A Nygren

BA Noord Van

JY Kim

Karim Bendjelid

M Kenosi

P Ray

PA Beest van

RJ Spruit

RS Smith

S Hyttel-Sorensen

S Strebel

SN Davie

Thomas W. L. Scheeren

TW Scheeren

English

PubMed

Scheeren, Thomas W. L.

Bendjelid, Karim

University of Groningen

   University of GroningenJournal of clinical monitoring and computing 2014 end of year summaryScheeren, Thomas W. L.; Bendjelid, KarimPublished in:Journal of clinical monitoring and computingDOI:10.1007/s10877-015-9689-4IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2015Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Scheeren, T. W. L., & Bendjelid, K. (2015). Journal of clinical monitoring and computing 2014 end of yearsummary: near infrared spectroscopy (NIRS). Journal of clinical monitoring and computing, 29(2), 217-220.https://doi.org/10.1007/s10877-015-9689-4CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 12-11-2019REVIEW PAPERJournal of clinical monitoring and computing 2014 end of yearsummary: near infrared spectroscopy (NIRS)Thomas W. L. Scheeren1,3 • Karim Bendjelid2Received: 13 February 2015 / Accepted: 13 February 2015 / Published online: 26 March 2015 The Author(s) 2015. This article is published with open access at Springerlink.comNear infrared spectroscopy (NIRS) is a non-invasivemethod for monitoring hemoglobin oxygen saturationwithin the microvessels. It is therefore also sometimes(erroneously) referred to as a measure of tissue oxygena-tion. By using self-adhesive optodes on the body surface,measurements can be taken in tissues below the skin up to adepth of 3–4 cm. The near infrared light (unlike visiblelight) even penetrates bone tissue, allowing measurementof regional cerebral oxygenation (SrcO2). There are nu-merous devices using NIRS technology available on themarket, and the main applications for use includemonitoring of SrcO2 during cardiothoracic and vascular(particularly carotid artery) surgery, as well as non-cardiacsurgery that is performed in the sitting or so-called beachchair position [1]. Another widespread use is the assess-ment of SrcO2 in neonates and preterm infants [2]. Fur-thermore, there have been attempts to use peripheral tissueoxygenation (SptO2) measurements by NIRS for guidingtherapy and predicting outcome in emergency medicine(both pre-hospital and emergency room use) and in theperioperative setting [3]. Finally, the ability to measureSptO2 at different sites [4] raised interest in researchers tolook at physiological changes, e.g. during exercise, inmusculature of the leg or arm. For this, a specialprovocation test (the vascular occlusion test (VOT) by in-flating a tourniquet proximal to the measurement site) hasbeen developed. The VOT looks at the rate of deoxy-genation during ischemia (vascular occlusion), which isconsidered as a measure of muscle and mitochondrialoxygen consumption, and at the rate of reoxygenationduring reperfusion, reflecting the reactivity of the micro-circulation [5].The Journal of Clinical Monitoring and Computing(JCMC) has become an ideal platform for publishingNIRS-related research, as reflected by an increasing num-ber of articles published in the recent years. This articlewill review two papers on peripheral (SptO2) and two pa-pers on cerebral hemoglobin oxygen saturation (SrcO2)published last year in the JCMC.1 NIRS for measuring peripheral hemoglobinoxygen saturationThe first two articles focus on a comparison of differentdevices measuring SptO2. Why is that an issue at all? Let’sgo back in time: Twenty years ago, with the first appear-ance of pulse oximeters in clinical use to measure periph-eral arterial oxygen saturation (SaO2), there were severalcompanies that developed and marketed such devices,which in turn incorporated different technologies (regard-ing wavelength used, measurement site etc.). As a conse-quence, at that time SaO2 had to be interpreted in view ofthe device used, and their readings could differ by severalpercentage points in individual patients. Nowadays, afterstandardization and technical progress of pulse oximetertechnologies, no one cares any longer with what device agiven SaO2 is measured, since variation between differentvendors has become negligible. With NIRS technology,& Thomas W. L. Scheerent.w.l.scheeren@umcg.nl1 Department of Anaesthesiology, University Medical CenterGroningen, Groningen, The Netherlands2 Department of Anaesthesiology and Intensive Care, IntensiveCare Service, Geneva University Hospitals, University ofGeneva, Geneva, Switzerland3 Department of Anaesthesiology, University of Groningen,Groningen, The Netherlands123J Clin Monit Comput (2015) 29:217–220DOI 10.1007/s10877-015-9689-4this standardisation process has still to be initiated, and weare currently confronted with a huge variety of devicesmeasuring regional hemoglobin oxygen saturation by using(one to four) different wavelengths, and come with multi-ple shaped optodes or sensors intended to be used at dif-ferent anatomic regions (forehead, thenar eminence,somatic organs, muscle etc.). This creates an area ofvalidation research of different NIRS applications, twoexamples of which are summarized in the followingchapter.The first study compares the use of two NIRS devices onSptO2 on the leg muscles of healthy human volunteers, withand without performing exercise [6]. Of note, only one ofthese devices (the InSpectra, Hutchinson Technologies) isproposed for this application, while the other one (the Invos4100, Somanetics) is primarily used for measuring SrcO2.Consequently, due to these different applications, the au-thors found a significant difference in muscle hemoglobinoxygen saturation of slightly more than 10 % already atbaseline (resting conditions), with the InSpectra showing thehigher values (87 ± 8 vs. 76 ± 6 %). The former was inclose agreement with baseline values (86 ± 6 %) observedwith the same device in 160 patients under general anaes-thesia [7]. During exercise, muscle hemoglobin oxygensaturation decreased immediately with both devices, tovalues close to zero (InSpectra) or slightly above 20 %(Invos) [6]. This decrease was reversible after cessation ofexercise, with slight hyperaemia of 8 % (InSpectra) and18 % above baseline values (Invos), respectively. The au-thors also performed a vascular occlusion test, which re-vealed similar results as the exercise test. Finally, theylooked at the influence of skin and subcutaneous tissuethickness as assessed by ultrasound on the measurements ofboth devices and found that the InSpectra, but not the Invos,was prone to increased skin and subcutaneous tissue thick-ness as reflected by lower SptO2 values. Since the measuringdepth within a tissue is determined by the distance betweenthe light-emitting and light-detecting part of the optode, thesmaller distance within the InSpectra sensor (30 mm ascompared to 40 mm in the Invos sensor) might explain itshigher susceptibility to thicker skin and subcutaneous tissue.The authors conclude that the Invos, although not primarilydesigned for this purpose, can be used to detect ex-perimentally and exercise induced skeletal muscle ischemiain the human leg, interchangeable with the InSpectra in thisrespect [6]. However, the study confirms the abovemen-tioned differences in sensitivity or calibration between NIRSdevices to detect changes in regional hemoglobin oxygensaturation.In the second study looking at peripheral hemoglobinoxygen saturation the authors compared the ability of threeNIRS devices (Invos 5100C, Nonin Equanox 7600, andFore-Sight, CASMed), all of which are primarily marketedfor cerebral and somatic use, to measure SptO2 on theforearm muscles of healthy human volunteers. [8] Themedian readings of the three devices at baseline werewithin 6 % points, with Invos giving the highest and Fore-Sight the lowest steady state values. To test the repeata-bility of the measurements the sensors were repositioned20 times on the forearm during hemodynamic steady stateconditions. The repeatability of Fore-Sight was best, whilethat of Equanox was worst, with no difference betweensame-site and various-site repeatability. Also, the authorsrepeatedly performed a VOT to induce maximal tissuedeoxygenation and to evaluate the dynamic properties ofthe three NIRS devices. The slopes of desaturation weresteepest with Equanox. Furthermore, Equanox and Invosoften reached their lower boundary values during ischemiaat a level of 20–30 % while Fore-Sight showed continuingdesaturation, likely best representing truly changing oxy-genation. This difference in dynamics found in SptO2measurements on the arm might also apply to measure-ments on the forehead, suggesting that differences in so-called removal of extra-cranial tissue contamination aspresented in a recent study [9] could be simply a matter ofdifferent sensitivity of NIRS devices to overall oxygena-tion changes in the tissue, as elegantly discussed by theauthors. The study has several clinical implications andconsequences when it comes to choosing a particular NIRSdevice: when NIRS oximetry is intended to be used fortrend monitoring, the repeatability of measurement is lessimportant. If in addition the sensitivity of a NIRS device tochanges in hemoglobin oxygen saturation is low, the risk ofundetected true hypoxia will be high. However, if NIRS isto be used as a spot measurement (e.g. in the emergencyroom) or if the monitoring is started when the patient statusis uncertain (e.g. in the ICU or OR in a deteriorating patientwithout having a baseline value), a good repeatability ofmeasurement or a close proximity to absolute (true) valuesbecomes more important. Since high sensitivity comes atthe expense of good repeatability, a pragmatic approachwould be to care less about the closeness to the ‘true’values, but to settle for the device with the best combina-tion of repeatability and sensitivity to changing oxygena-tion [8].2 NIRS for measuring cerebral hemoglobinoxygen saturationThe most commonly used application for NIRS technologyis monitoring cerebral hemoglobin oxygen saturation(SrcO2). A recently developed use includes patients un-dergoing arthroscopic shoulder surgery in the sitting posi-tion, which is preferred in some centers despite the dangerof hemodynamic instability for the sake of better surgical218 J Clin Monit Comput (2015) 29:217–220123conditions. Although it is known that SrcO2 is lower underthose conditions as compared to the alternative lateral de-cubitus position, the clinical relevant question arises whe-ther intravenous anesthesia or inhalational anesthesia issuperior when it comes to preserving cerebral oxygenation.This question was investigated in a recent trial, in which 40patients were randomized to receive either propofol ordesflurane, both titrated to similar anesthetic depth as ob-tained by bispectral index (BIS), resulting also in similarhemodynamics [10]. While SrcO2 significantly decreasedin both groups in the first minutes after patients were lo-cated from the supine to the sitting position, values re-mained significantly higher in the desflurane group ascompared to the propofol group, despite lower bloodpressures. Furthermore, cerebral desaturations, defined asSrcO2 below 75 % of individual baseline values, occurredin two patients of the propofol group but in none of thedesflurane group. Unfortunately, measurements werestopped 9 min after positioning of the patients, preventingconclusions on the intraoperative course of SrcO2 as wellas on-going differences between anesthetic agents. Theauthors conclude that desflurane preserved cerebral oxy-genation better than propofol at equipotent anestheticconcentrations [10]. These observations are surprising atfirst sight, since it is long known that volatile anestheticsimpair autoregulation of cerebral blood flow more thanpropofol [11]. The authors speculate that desflurane (unlikepropofol) induced cerebral vasodilation and thus increasedcerebral blood flow (CBF), which in turn compensates thereduction in CBF following installation of the sitting po-sition. Otherwise, we may also speculate that the negativeimpact of propofol on venous return and thus cardiacoutput is huge in the present posture due to the venodilatoreffect of the drug.Another example of the clinical applicability of NIRStechnology to measure SrcO2 is presented in a case seriesof 20 patients undergoing major abdominal or urologicalsurgery under general anaesthesia [12]. The authors usedcontrolled hypotension induced by nitroglycerin (NTG) inorder to minimize blood loss and optimise surgical condi-tions. Vasodilation with NTG reduced MAP by about 20 %(from 90 ± 14 to 72 ± 14 mmHg), whereas it increasedSrcO2 in all patients by an average between 15 and 21 %.Although the authors did not measure blood flow (e.g.cardiac output) and did not report what NIRS device theyused, these findings demonstrate that blood pressure andtissue perfusion are not always related in a linear, positivefashion (uncoupling phenomenon). The authors discuss asa potential confounder that the volatile anaesthetics usedmight have led to luxury perfusion of the monitored brainarea while diverting blood away from potentially ischemicregions. [12] Nevertheless, this case series shows thatNIRS monitoring can be used to ensure the adequacy oftissue oxygenation during controlled hypotension and ex-pands the scope of conventional hemodynamic monitoringin this respect. This way it may contribute to improvepatient’s safety in case of macro-microcirculatorydecoupling.3 Interpretation of SrcO2 valuesSince there is no consensus about what should be consid-ered ‘‘normal values’’ for cerebral hemoglobin oxygensaturation, the authors of the previous study [8] come upwith a very interesting calculation: Assuming that a jugularbulb saturation (SjbO2, the gold standard for assessingcerebral hypoxemia) below 50 % indicates cerebral is-chemia, then with a ratio between arterial and venous bloodvolumes of 25:75 contributing to the SrcO2 signal dis-played on the monitor, as most NIRS devices adopt, we cancalculate which readings actually indicate cerebral is-chemia and which readings may assure us that this is notthe case [8]. In detail, if the SaO2 is 95 % and SjbO2 50 %,the resulting SrcO2 should be 61 %, which can be con-sidered as ‘‘normal’’. Thus with a standard deviation of5 % a SrcO2 measurement should be below 52 % (61-1.96 9 5 %) to be more than 95 % certain that the tissue isactually ischemic and above 71 % (61 ? 1.96 9 5 %) tobe certain that it is not, implying a large ‘‘grey zone’’ ofSrcO2 values where its diagnostic ability is inconclusive[13]. On the other hand, changing of the body position (e.g.head-up or head-down tilting) may change the ratio be-tween arterial and venous blood volumes of 25:75, so thatfor instance decreases in the SrcO2 readings are simply theresults of an increased proportion of venous blood con-tributing to the signal, rather than a true change in cerebraltissue oxygenation. In this respect, the higher SrcO2 valuesafter raising patients to the sitting position during desflu-rane anesthesia in the abovementioned study [10] could beinterpreted as evidence for cerebral arterial vasodilationunder desflurane and maintained cerebrovascular tone un-der propofol anesthesia.In conclusion, until a standardization of NIRS deviceshas been effectuated, the clinical context may influence thechoice of the adequate NIRS device for a specific purpose.Open Access This article is distributed under the terms of theCreative Commons Attribution License which permits any use, dis-tribution, and reproduction in any medium, provided the originalauthor(s) and the source are credited.References1. Scheeren TW, Schober P, Schwarte LA. Monitoring tissue oxy-genation by near infrared spectroscopy (NIRS): background andJ Clin Monit Comput (2015) 29:217–220 219123current applications. J Clin Monit Comput. 2012;26(4):279–87.doi:10.1007/s10877-012-9348-y.2. Kenosi M, Naulaers G, Ryan C, Dempsey E. Current researchsuggests that the future looks brighter for cerebral oxygenationmonitoring in preterm infants. Acta Paediatr. 2015;104(3):225–31. doi:10.1111/apa.12906.3. van Beest PA, Vos JJ, Poterman M, Kalmar AF, Scheeren TW.Tissue oxygenation as a target for goal-directed therapy in high-risk surgery: a pilot study. BMC Anesthesiol. 2014;14:122.doi:10.1186/1471-2253-14-122.4. van Beest PA, Scheeren TW. Tissue oxygen saturation as a goal,but when and where should we measure it? J Clin Monit Comput.2013;27(3):211–3. doi:10.1007/s10877-013-9438-5.5. Smith RS, Murkin JM. A novel assessment of peripheral tissuemicrocirculatory vasoreactivity using vascular occlusion testingduring cardiopulmonary bypass. J Cardiothorac Vasc Anesth.2014;28(5):1217–20. doi:10.1053/j.jvca.2014.03.016.6. Nygren A, Rennerfelt K, Zhang Q. Detection of changes inmuscle oxygen saturation in the human leg: a comparison of twonear-infrared spectroscopy devices. J Clin Monit Comput.2014;28(1):57–62. doi:10.1007/s10877-013-9494-x.7. Spruit RJ, Schwarte LA, Hakenberg OW, Scheeren TW. Asso-ciation of intraoperative tissue oxygenation with suspected riskfactors for tissue hypoxia. J Clin Monit Comput. 2013;27(5):541–50. doi:10.1007/s10877-013-9460-7.8. Hyttel-Sorensen S, Hessel TW, Greisen G. Peripheral tissueoximetry: comparing three commercial near-infrared spectroscopyoximeters on the forearm. J Clin Monit Comput. 2014;28(2):149–55. doi:10.1007/s10877-013-9507-9.9. Davie SN, Grocott HP. Impact of extracranial contamination onregional cerebral oxygen saturation: a comparison of three cere-bral oximetry technologies. Anesthesiology. 2012;116(4):834–40. doi:10.1097/ALN.0b013e31824c00d7.10. Kim JY, Lee JS, Lee KC, Kim HS, Kim SH, Kwak HJ. The effectof desflurane versus propofol on regional cerebral oxygenation inthe sitting position for shoulder arthroscopy. J Clin MonitComput. 2014;28(4):371–6. doi:10.1007/s10877-013-9543-5.11. Strebel S, Lam AM, Matta B, Mayberg TS, Aaslid R, NewellDW. Dynamic and static cerebral autoregulation during isoflu-rane, desflurane, and propofol anesthesia. Anesthesiology.1995;83(1):66–76.12. Van Noord BA, Stalker CL, Roffey P, Thangathurai D. The useof regional cerebral oximetry monitoring during controlled hy-potension: a case series. J Clin Monit Comput. 2014;28(3):319–23. doi:10.1007/s10877-013-9523-9.13. Ray P, Le Manach Y, Riou B, Houle TT. Statistical evaluation ofa biomarker. Anesthesiology. 2010;112(4):1023–40. doi:10.1097/ALN.0b013e3181d47604.220 J Clin Monit Comput (2015) 29:217–220123

Journal of clinical monitoring and computing 2014 end of year summary:near infrared spectroscopy (NIRS)

Dissertations of the University of Groningen

   University of GroningenJournal of clinical monitoring and computing 2014 end of year summaryScheeren, Thomas W. L.; Bendjelid, KarimPublished in:Journal of clinical monitoring and computingDOI:10.1007/s10877-015-9689-4IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2015Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Scheeren, T. W. L., & Bendjelid, K. (2015). Journal of clinical monitoring and computing 2014 end of yearsummary: near infrared spectroscopy (NIRS). Journal of clinical monitoring and computing, 29(2), 217-220.https://doi.org/10.1007/s10877-015-9689-4CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 09-09-2023REVIEW PAPERJournal of clinical monitoring and computing 2014 end of yearsummary: near infrared spectroscopy (NIRS)Thomas W. L. Scheeren1,3 • Karim Bendjelid2Received: 13 February 2015 / Accepted: 13 February 2015 / Published online: 26 March 2015 The Author(s) 2015. This article is published with open access at Springerlink.comNear infrared spectroscopy (NIRS) is a non-invasivemethod for monitoring hemoglobin oxygen saturationwithin the microvessels. It is therefore also sometimes(erroneously) referred to as a measure of tissue oxygena-tion. By using self-adhesive optodes on the body surface,measurements can be taken in tissues below the skin up to adepth of 3–4 cm. The near infrared light (unlike visiblelight) even penetrates bone tissue, allowing measurementof regional cerebral oxygenation (SrcO2). There are nu-merous devices using NIRS technology available on themarket, and the main applications for use includemonitoring of SrcO2 during cardiothoracic and vascular(particularly carotid artery) surgery, as well as non-cardiacsurgery that is performed in the sitting or so-called beachchair position [1]. Another widespread use is the assess-ment of SrcO2 in neonates and preterm infants [2]. Fur-thermore, there have been attempts to use peripheral tissueoxygenation (SptO2) measurements by NIRS for guidingtherapy and predicting outcome in emergency medicine(both pre-hospital and emergency room use) and in theperioperative setting [3]. Finally, the ability to measureSptO2 at different sites [4] raised interest in researchers tolook at physiological changes, e.g. during exercise, inmusculature of the leg or arm. For this, a specialprovocation test (the vascular occlusion test (VOT) by in-flating a tourniquet proximal to the measurement site) hasbeen developed. The VOT looks at the rate of deoxy-genation during ischemia (vascular occlusion), which isconsidered as a measure of muscle and mitochondrialoxygen consumption, and at the rate of reoxygenationduring reperfusion, reflecting the reactivity of the micro-circulation [5].The Journal of Clinical Monitoring and Computing(JCMC) has become an ideal platform for publishingNIRS-related research, as reflected by an increasing num-ber of articles published in the recent years. This articlewill review two papers on peripheral (SptO2) and two pa-pers on cerebral hemoglobin oxygen saturation (SrcO2)published last year in the JCMC.1 NIRS for measuring peripheral hemoglobinoxygen saturationThe first two articles focus on a comparison of differentdevices measuring SptO2. Why is that an issue at all? Let’sgo back in time: Twenty years ago, with the first appear-ance of pulse oximeters in clinical use to measure periph-eral arterial oxygen saturation (SaO2), there were severalcompanies that developed and marketed such devices,which in turn incorporated different technologies (regard-ing wavelength used, measurement site etc.). As a conse-quence, at that time SaO2 had to be interpreted in view ofthe device used, and their readings could differ by severalpercentage points in individual patients. Nowadays, afterstandardization and technical progress of pulse oximetertechnologies, no one cares any longer with what device agiven SaO2 is measured, since variation between differentvendors has become negligible. With NIRS technology,& Thomas W. L. Scheerent.w.l.scheeren@umcg.nl1 Department of Anaesthesiology, University Medical CenterGroningen, Groningen, The Netherlands2 Department of Anaesthesiology and Intensive Care, IntensiveCare Service, Geneva University Hospitals, University ofGeneva, Geneva, Switzerland3 Department of Anaesthesiology, University of Groningen,Groningen, The Netherlands123J Clin Monit Comput (2015) 29:217–220DOI 10.1007/s10877-015-9689-4this standardisation process has still to be initiated, and weare currently confronted with a huge variety of devicesmeasuring regional hemoglobin oxygen saturation by using(one to four) different wavelengths, and come with multi-ple shaped optodes or sensors intended to be used at dif-ferent anatomic regions (forehead, thenar eminence,somatic organs, muscle etc.). This creates an area ofvalidation research of different NIRS applications, twoexamples of which are summarized in the followingchapter.The first study compares the use of two NIRS devices onSptO2 on the leg muscles of healthy human volunteers, withand without performing exercise [6]. Of note, only one ofthese devices (the InSpectra, Hutchinson Technologies) isproposed for this application, while the other one (the Invos4100, Somanetics) is primarily used for measuring SrcO2.Consequently, due to these different applications, the au-thors found a significant difference in muscle hemoglobinoxygen saturation of slightly more than 10 % already atbaseline (resting conditions), with the InSpectra showing thehigher values (87 ± 8 vs. 76 ± 6 %). The former was inclose agreement with baseline values (86 ± 6 %) observedwith the same device in 160 patients under general anaes-thesia [7]. During exercise, muscle hemoglobin oxygensaturation decreased immediately with both devices, tovalues close to zero (InSpectra) or slightly above 20 %(Invos) [6]. This decrease was reversible after cessation ofexercise, with slight hyperaemia of 8 % (InSpectra) and18 % above baseline values (Invos), respectively. The au-thors also performed a vascular occlusion test, which re-vealed similar results as the exercise test. Finally, theylooked at the influence of skin and subcutaneous tissuethickness as assessed by ultrasound on the measurements ofboth devices and found that the InSpectra, but not the Invos,was prone to increased skin and subcutaneous tissue thick-ness as reflected by lower SptO2 values. Since the measuringdepth within a tissue is determined by the distance betweenthe light-emitting and light-detecting part of the optode, thesmaller distance within the InSpectra sensor (30 mm ascompared to 40 mm in the Invos sensor) might explain itshigher susceptibility to thicker skin and subcutaneous tissue.The authors conclude that the Invos, although not primarilydesigned for this purpose, can be used to detect ex-perimentally and exercise induced skeletal muscle ischemiain the human leg, interchangeable with the InSpectra in thisrespect [6]. However, the study confirms the abovemen-tioned differences in sensitivity or calibration between NIRSdevices to detect changes in regional hemoglobin oxygensaturation.In the second study looking at peripheral hemoglobinoxygen saturation the authors compared the ability of threeNIRS devices (Invos 5100C, Nonin Equanox 7600, andFore-Sight, CASMed), all of which are primarily marketedfor cerebral and somatic use, to measure SptO2 on theforearm muscles of healthy human volunteers. [8] Themedian readings of the three devices at baseline werewithin 6 % points, with Invos giving the highest and Fore-Sight the lowest steady state values. To test the repeata-bility of the measurements the sensors were repositioned20 times on the forearm during hemodynamic steady stateconditions. The repeatability of Fore-Sight was best, whilethat of Equanox was worst, with no difference betweensame-site and various-site repeatability. Also, the authorsrepeatedly performed a VOT to induce maximal tissuedeoxygenation and to evaluate the dynamic properties ofthe three NIRS devices. The slopes of desaturation weresteepest with Equanox. Furthermore, Equanox and Invosoften reached their lower boundary values during ischemiaat a level of 20–30 % while Fore-Sight showed continuingdesaturation, likely best representing truly changing oxy-genation. This difference in dynamics found in SptO2measurements on the arm might also apply to measure-ments on the forehead, suggesting that differences in so-called removal of extra-cranial tissue contamination aspresented in a recent study [9] could be simply a matter ofdifferent sensitivity of NIRS devices to overall oxygena-tion changes in the tissue, as elegantly discussed by theauthors. The study has several clinical implications andconsequences when it comes to choosing a particular NIRSdevice: when NIRS oximetry is intended to be used fortrend monitoring, the repeatability of measurement is lessimportant. If in addition the sensitivity of a NIRS device tochanges in hemoglobin oxygen saturation is low, the risk ofundetected true hypoxia will be high. However, if NIRS isto be used as a spot measurement (e.g. in the emergencyroom) or if the monitoring is started when the patient statusis uncertain (e.g. in the ICU or OR in a deteriorating patientwithout having a baseline value), a good repeatability ofmeasurement or a close proximity to absolute (true) valuesbecomes more important. Since high sensitivity comes atthe expense of good repeatability, a pragmatic approachwould be to care less about the closeness to the ‘true’values, but to settle for the device with the best combina-tion of repeatability and sensitivity to changing oxygena-tion [8].2 NIRS for measuring cerebral hemoglobinoxygen saturationThe most commonly used application for NIRS technologyis monitoring cerebral hemoglobin oxygen saturation(SrcO2). A recently developed use includes patients un-dergoing arthroscopic shoulder surgery in the sitting posi-tion, which is preferred in some centers despite the dangerof hemodynamic instability for the sake of better surgical218 J Clin Monit Comput (2015) 29:217–220123conditions. Although it is known that SrcO2 is lower underthose conditions as compared to the alternative lateral de-cubitus position, the clinical relevant question arises whe-ther intravenous anesthesia or inhalational anesthesia issuperior when it comes to preserving cerebral oxygenation.This question was investigated in a recent trial, in which 40patients were randomized to receive either propofol ordesflurane, both titrated to similar anesthetic depth as ob-tained by bispectral index (BIS), resulting also in similarhemodynamics [10]. While SrcO2 significantly decreasedin both groups in the first minutes after patients were lo-cated from the supine to the sitting position, values re-mained significantly higher in the desflurane group ascompared to the propofol group, despite lower bloodpressures. Furthermore, cerebral desaturations, defined asSrcO2 below 75 % of individual baseline values, occurredin two patients of the propofol group but in none of thedesflurane group. Unfortunately, measurements werestopped 9 min after positioning of the patients, preventingconclusions on the intraoperative course of SrcO2 as wellas on-going differences between anesthetic agents. Theauthors conclude that desflurane preserved cerebral oxy-genation better than propofol at equipotent anestheticconcentrations [10]. These observations are surprising atfirst sight, since it is long known that volatile anestheticsimpair autoregulation of cerebral blood flow more thanpropofol [11]. The authors speculate that desflurane (unlikepropofol) induced cerebral vasodilation and thus increasedcerebral blood flow (CBF), which in turn compensates thereduction in CBF following installation of the sitting po-sition. Otherwise, we may also speculate that the negativeimpact of propofol on venous return and thus cardiacoutput is huge in the present posture due to the venodilatoreffect of the drug.Another example of the clinical applicability of NIRStechnology to measure SrcO2 is presented in a case seriesof 20 patients undergoing major abdominal or urologicalsurgery under general anaesthesia [12]. The authors usedcontrolled hypotension induced by nitroglycerin (NTG) inorder to minimize blood loss and optimise surgical condi-tions. Vasodilation with NTG reduced MAP by about 20 %(from 90 ± 14 to 72 ± 14 mmHg), whereas it increasedSrcO2 in all patients by an average between 15 and 21 %.Although the authors did not measure blood flow (e.g.cardiac output) and did not report what NIRS device theyused, these findings demonstrate that blood pressure andtissue perfusion are not always related in a linear, positivefashion (uncoupling phenomenon). The authors discuss asa potential confounder that the volatile anaesthetics usedmight have led to luxury perfusion of the monitored brainarea while diverting blood away from potentially ischemicregions. [12] Nevertheless, this case series shows thatNIRS monitoring can be used to ensure the adequacy oftissue oxygenation during controlled hypotension and ex-pands the scope of conventional hemodynamic monitoringin this respect. This way it may contribute to improvepatient’s safety in case of macro-microcirculatorydecoupling.3 Interpretation of SrcO2 valuesSince there is no consensus about what should be consid-ered ‘‘normal values’’ for cerebral hemoglobin oxygensaturation, the authors of the previous study [8] come upwith a very interesting calculation: Assuming that a jugularbulb saturation (SjbO2, the gold standard for assessingcerebral hypoxemia) below 50 % indicates cerebral is-chemia, then with a ratio between arterial and venous bloodvolumes of 25:75 contributing to the SrcO2 signal dis-played on the monitor, as most NIRS devices adopt, we cancalculate which readings actually indicate cerebral is-chemia and which readings may assure us that this is notthe case [8]. In detail, if the SaO2 is 95 % and SjbO2 50 %,the resulting SrcO2 should be 61 %, which can be con-sidered as ‘‘normal’’. Thus with a standard deviation of5 % a SrcO2 measurement should be below 52 % (61-1.96 9 5 %) to be more than 95 % certain that the tissue isactually ischemic and above 71 % (61 ? 1.96 9 5 %) tobe certain that it is not, implying a large ‘‘grey zone’’ ofSrcO2 values where its diagnostic ability is inconclusive[13]. On the other hand, changing of the body position (e.g.head-up or head-down tilting) may change the ratio be-tween arterial and venous blood volumes of 25:75, so thatfor instance decreases in the SrcO2 readings are simply theresults of an increased proportion of venous blood con-tributing to the signal, rather than a true change in cerebraltissue oxygenation. In this respect, the higher SrcO2 valuesafter raising patients to the sitting position during desflu-rane anesthesia in the abovementioned study [10] could beinterpreted as evidence for cerebral arterial vasodilationunder desflurane and maintained cerebrovascular tone un-der propofol anesthesia.In conclusion, until a standardization of NIRS deviceshas been effectuated, the clinical context may influence thechoice of the adequate NIRS device for a specific purpose.Open Access This article is distributed under the terms of theCreative Commons Attribution License which permits any use, dis-tribution, and reproduction in any medium, provided the originalauthor(s) and the source are credited.References1. Scheeren TW, Schober P, Schwarte LA. Monitoring tissue oxy-genation by near infrared spectroscopy (NIRS): background andJ Clin Monit Comput (2015) 29:217–220 219123current applications. J Clin Monit Comput. 2012;26(4):279–87.doi:10.1007/s10877-012-9348-y.2. Kenosi M, Naulaers G, Ryan C, Dempsey E. Current researchsuggests that the future looks brighter for cerebral oxygenationmonitoring in preterm infants. Acta Paediatr. 2015;104(3):225–31. doi:10.1111/apa.12906.3. van Beest PA, Vos JJ, Poterman M, Kalmar AF, Scheeren TW.Tissue oxygenation as a target for goal-directed therapy in high-risk surgery: a pilot study. BMC Anesthesiol. 2014;14:122.doi:10.1186/1471-2253-14-122.4. van Beest PA, Scheeren TW. Tissue oxygen saturation as a goal,but when and where should we measure it? J Clin Monit Comput.2013;27(3):211–3. doi:10.1007/s10877-013-9438-5.5. Smith RS, Murkin JM. A novel assessment of peripheral tissuemicrocirculatory vasoreactivity using vascular occlusion testingduring cardiopulmonary bypass. J Cardiothorac Vasc Anesth.2014;28(5):1217–20. doi:10.1053/j.jvca.2014.03.016.6. Nygren A, Rennerfelt K, Zhang Q. Detection of changes inmuscle oxygen saturation in the human leg: a comparison of twonear-infrared spectroscopy devices. J Clin Monit Comput.2014;28(1):57–62. doi:10.1007/s10877-013-9494-x.7. Spruit RJ, Schwarte LA, Hakenberg OW, Scheeren TW. Asso-ciation of intraoperative tissue oxygenation with suspected riskfactors for tissue hypoxia. J Clin Monit Comput. 2013;27(5):541–50. doi:10.1007/s10877-013-9460-7.8. Hyttel-Sorensen S, Hessel TW, Greisen G. Peripheral tissueoximetry: comparing three commercial near-infrared spectroscopyoximeters on the forearm. J Clin Monit Comput. 2014;28(2):149–55. doi:10.1007/s10877-013-9507-9.9. Davie SN, Grocott HP. Impact of extracranial contamination onregional cerebral oxygen saturation: a comparison of three cere-bral oximetry technologies. Anesthesiology. 2012;116(4):834–40. doi:10.1097/ALN.0b013e31824c00d7.10. Kim JY, Lee JS, Lee KC, Kim HS, Kim SH, Kwak HJ. The effectof desflurane versus propofol on regional cerebral oxygenation inthe sitting position for shoulder arthroscopy. J Clin MonitComput. 2014;28(4):371–6. doi:10.1007/s10877-013-9543-5.11. Strebel S, Lam AM, Matta B, Mayberg TS, Aaslid R, NewellDW. Dynamic and static cerebral autoregulation during isoflu-rane, desflurane, and propofol anesthesia. Anesthesiology.1995;83(1):66–76.12. Van Noord BA, Stalker CL, Roffey P, Thangathurai D. The useof regional cerebral oximetry monitoring during controlled hy-potension: a case series. J Clin Monit Comput. 2014;28(3):319–23. doi:10.1007/s10877-013-9523-9.13. Ray P, Le Manach Y, Riou B, Houle TT. Statistical evaluation ofa biomarker. Anesthesiology. 2010;112(4):1023–40. doi:10.1097/ALN.0b013e3181d47604.220 J Clin Monit Comput (2015) 29:217–220123

ARTS repository - University of Groningen

   University of GroningenJournal of clinical monitoring and computing 2014 end of year summaryScheeren, Thomas W. L.; Bendjelid, KarimPublished in:Journal of clinical monitoring and computingDOI:10.1007/s10877-015-9689-4IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2015Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Scheeren, T. W. L., & Bendjelid, K. (2015). Journal of clinical monitoring and computing 2014 end of yearsummary: near infrared spectroscopy (NIRS). Journal of clinical monitoring and computing, 29(2), 217-220.https://doi.org/10.1007/s10877-015-9689-4CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 05-06-2022REVIEW PAPERJournal of clinical monitoring and computing 2014 end of yearsummary: near infrared spectroscopy (NIRS)Thomas W. L. Scheeren1,3 • Karim Bendjelid2Received: 13 February 2015 / Accepted: 13 February 2015 / Published online: 26 March 2015 The Author(s) 2015. This article is published with open access at Springerlink.comNear infrared spectroscopy (NIRS) is a non-invasivemethod for monitoring hemoglobin oxygen saturationwithin the microvessels. It is therefore also sometimes(erroneously) referred to as a measure of tissue oxygena-tion. By using self-adhesive optodes on the body surface,measurements can be taken in tissues below the skin up to adepth of 3–4 cm. The near infrared light (unlike visiblelight) even penetrates bone tissue, allowing measurementof regional cerebral oxygenation (SrcO2). There are nu-merous devices using NIRS technology available on themarket, and the main applications for use includemonitoring of SrcO2 during cardiothoracic and vascular(particularly carotid artery) surgery, as well as non-cardiacsurgery that is performed in the sitting or so-called beachchair position [1]. Another widespread use is the assess-ment of SrcO2 in neonates and preterm infants [2]. Fur-thermore, there have been attempts to use peripheral tissueoxygenation (SptO2) measurements by NIRS for guidingtherapy and predicting outcome in emergency medicine(both pre-hospital and emergency room use) and in theperioperative setting [3]. Finally, the ability to measureSptO2 at different sites [4] raised interest in researchers tolook at physiological changes, e.g. during exercise, inmusculature of the leg or arm. For this, a specialprovocation test (the vascular occlusion test (VOT) by in-flating a tourniquet proximal to the measurement site) hasbeen developed. The VOT looks at the rate of deoxy-genation during ischemia (vascular occlusion), which isconsidered as a measure of muscle and mitochondrialoxygen consumption, and at the rate of reoxygenationduring reperfusion, reflecting the reactivity of the micro-circulation [5].The Journal of Clinical Monitoring and Computing(JCMC) has become an ideal platform for publishingNIRS-related research, as reflected by an increasing num-ber of articles published in the recent years. This articlewill review two papers on peripheral (SptO2) and two pa-pers on cerebral hemoglobin oxygen saturation (SrcO2)published last year in the JCMC.1 NIRS for measuring peripheral hemoglobinoxygen saturationThe first two articles focus on a comparison of differentdevices measuring SptO2. Why is that an issue at all? Let’sgo back in time: Twenty years ago, with the first appear-ance of pulse oximeters in clinical use to measure periph-eral arterial oxygen saturation (SaO2), there were severalcompanies that developed and marketed such devices,which in turn incorporated different technologies (regard-ing wavelength used, measurement site etc.). As a conse-quence, at that time SaO2 had to be interpreted in view ofthe device used, and their readings could differ by severalpercentage points in individual patients. Nowadays, afterstandardization and technical progress of pulse oximetertechnologies, no one cares any longer with what device agiven SaO2 is measured, since variation between differentvendors has become negligible. With NIRS technology,& Thomas W. L. Scheerent.w.l.scheeren@umcg.nl1 Department of Anaesthesiology, University Medical CenterGroningen, Groningen, The Netherlands2 Department of Anaesthesiology and Intensive Care, IntensiveCare Service, Geneva University Hospitals, University ofGeneva, Geneva, Switzerland3 Department of Anaesthesiology, University of Groningen,Groningen, The Netherlands123J Clin Monit Comput (2015) 29:217–220DOI 10.1007/s10877-015-9689-4this standardisation process has still to be initiated, and weare currently confronted with a huge variety of devicesmeasuring regional hemoglobin oxygen saturation by using(one to four) different wavelengths, and come with multi-ple shaped optodes or sensors intended to be used at dif-ferent anatomic regions (forehead, thenar eminence,somatic organs, muscle etc.). This creates an area ofvalidation research of different NIRS applications, twoexamples of which are summarized in the followingchapter.The first study compares the use of two NIRS devices onSptO2 on the leg muscles of healthy human volunteers, withand without performing exercise [6]. Of note, only one ofthese devices (the InSpectra, Hutchinson Technologies) isproposed for this application, while the other one (the Invos4100, Somanetics) is primarily used for measuring SrcO2.Consequently, due to these different applications, the au-thors found a significant difference in muscle hemoglobinoxygen saturation of slightly more than 10 % already atbaseline (resting conditions), with the InSpectra showing thehigher values (87 ± 8 vs. 76 ± 6 %). The former was inclose agreement with baseline values (86 ± 6 %) observedwith the same device in 160 patients under general anaes-thesia [7]. During exercise, muscle hemoglobin oxygensaturation decreased immediately with both devices, tovalues close to zero (InSpectra) or slightly above 20 %(Invos) [6]. This decrease was reversible after cessation ofexercise, with slight hyperaemia of 8 % (InSpectra) and18 % above baseline values (Invos), respectively. The au-thors also performed a vascular occlusion test, which re-vealed similar results as the exercise test. Finally, theylooked at the influence of skin and subcutaneous tissuethickness as assessed by ultrasound on the measurements ofboth devices and found that the InSpectra, but not the Invos,was prone to increased skin and subcutaneous tissue thick-ness as reflected by lower SptO2 values. Since the measuringdepth within a tissue is determined by the distance betweenthe light-emitting and light-detecting part of the optode, thesmaller distance within the InSpectra sensor (30 mm ascompared to 40 mm in the Invos sensor) might explain itshigher susceptibility to thicker skin and subcutaneous tissue.The authors conclude that the Invos, although not primarilydesigned for this purpose, can be used to detect ex-perimentally and exercise induced skeletal muscle ischemiain the human leg, interchangeable with the InSpectra in thisrespect [6]. However, the study confirms the abovemen-tioned differences in sensitivity or calibration between NIRSdevices to detect changes in regional hemoglobin oxygensaturation.In the second study looking at peripheral hemoglobinoxygen saturation the authors compared the ability of threeNIRS devices (Invos 5100C, Nonin Equanox 7600, andFore-Sight, CASMed), all of which are primarily marketedfor cerebral and somatic use, to measure SptO2 on theforearm muscles of healthy human volunteers. [8] Themedian readings of the three devices at baseline werewithin 6 % points, with Invos giving the highest and Fore-Sight the lowest steady state values. To test the repeata-bility of the measurements the sensors were repositioned20 times on the forearm during hemodynamic steady stateconditions. The repeatability of Fore-Sight was best, whilethat of Equanox was worst, with no difference betweensame-site and various-site repeatability. Also, the authorsrepeatedly performed a VOT to induce maximal tissuedeoxygenation and to evaluate the dynamic properties ofthe three NIRS devices. The slopes of desaturation weresteepest with Equanox. Furthermore, Equanox and Invosoften reached their lower boundary values during ischemiaat a level of 20–30 % while Fore-Sight showed continuingdesaturation, likely best representing truly changing oxy-genation. This difference in dynamics found in SptO2measurements on the arm might also apply to measure-ments on the forehead, suggesting that differences in so-called removal of extra-cranial tissue contamination aspresented in a recent study [9] could be simply a matter ofdifferent sensitivity of NIRS devices to overall oxygena-tion changes in the tissue, as elegantly discussed by theauthors. The study has several clinical implications andconsequences when it comes to choosing a particular NIRSdevice: when NIRS oximetry is intended to be used fortrend monitoring, the repeatability of measurement is lessimportant. If in addition the sensitivity of a NIRS device tochanges in hemoglobin oxygen saturation is low, the risk ofundetected true hypoxia will be high. However, if NIRS isto be used as a spot measurement (e.g. in the emergencyroom) or if the monitoring is started when the patient statusis uncertain (e.g. in the ICU or OR in a deteriorating patientwithout having a baseline value), a good repeatability ofmeasurement or a close proximity to absolute (true) valuesbecomes more important. Since high sensitivity comes atthe expense of good repeatability, a pragmatic approachwould be to care less about the closeness to the ‘true’values, but to settle for the device with the best combina-tion of repeatability and sensitivity to changing oxygena-tion [8].2 NIRS for measuring cerebral hemoglobinoxygen saturationThe most commonly used application for NIRS technologyis monitoring cerebral hemoglobin oxygen saturation(SrcO2). A recently developed use includes patients un-dergoing arthroscopic shoulder surgery in the sitting posi-tion, which is preferred in some centers despite the dangerof hemodynamic instability for the sake of better surgical218 J Clin Monit Comput (2015) 29:217–220123conditions. Although it is known that SrcO2 is lower underthose conditions as compared to the alternative lateral de-cubitus position, the clinical relevant question arises whe-ther intravenous anesthesia or inhalational anesthesia issuperior when it comes to preserving cerebral oxygenation.This question was investigated in a recent trial, in which 40patients were randomized to receive either propofol ordesflurane, both titrated to similar anesthetic depth as ob-tained by bispectral index (BIS), resulting also in similarhemodynamics [10]. While SrcO2 significantly decreasedin both groups in the first minutes after patients were lo-cated from the supine to the sitting position, values re-mained significantly higher in the desflurane group ascompared to the propofol group, despite lower bloodpressures. Furthermore, cerebral desaturations, defined asSrcO2 below 75 % of individual baseline values, occurredin two patients of the propofol group but in none of thedesflurane group. Unfortunately, measurements werestopped 9 min after positioning of the patients, preventingconclusions on the intraoperative course of SrcO2 as wellas on-going differences between anesthetic agents. Theauthors conclude that desflurane preserved cerebral oxy-genation better than propofol at equipotent anestheticconcentrations [10]. These observations are surprising atfirst sight, since it is long known that volatile anestheticsimpair autoregulation of cerebral blood flow more thanpropofol [11]. The authors speculate that desflurane (unlikepropofol) induced cerebral vasodilation and thus increasedcerebral blood flow (CBF), which in turn compensates thereduction in CBF following installation of the sitting po-sition. Otherwise, we may also speculate that the negativeimpact of propofol on venous return and thus cardiacoutput is huge in the present posture due to the venodilatoreffect of the drug.Another example of the clinical applicability of NIRStechnology to measure SrcO2 is presented in a case seriesof 20 patients undergoing major abdominal or urologicalsurgery under general anaesthesia [12]. The authors usedcontrolled hypotension induced by nitroglycerin (NTG) inorder to minimize blood loss and optimise surgical condi-tions. Vasodilation with NTG reduced MAP by about 20 %(from 90 ± 14 to 72 ± 14 mmHg), whereas it increasedSrcO2 in all patients by an average between 15 and 21 %.Although the authors did not measure blood flow (e.g.cardiac output) and did not report what NIRS device theyused, these findings demonstrate that blood pressure andtissue perfusion are not always related in a linear, positivefashion (uncoupling phenomenon). The authors discuss asa potential confounder that the volatile anaesthetics usedmight have led to luxury perfusion of the monitored brainarea while diverting blood away from potentially ischemicregions. [12] Nevertheless, this case series shows thatNIRS monitoring can be used to ensure the adequacy oftissue oxygenation during controlled hypotension and ex-pands the scope of conventional hemodynamic monitoringin this respect. This way it may contribute to improvepatient’s safety in case of macro-microcirculatorydecoupling.3 Interpretation of SrcO2 valuesSince there is no consensus about what should be consid-ered ‘‘normal values’’ for cerebral hemoglobin oxygensaturation, the authors of the previous study [8] come upwith a very interesting calculation: Assuming that a jugularbulb saturation (SjbO2, the gold standard for assessingcerebral hypoxemia) below 50 % indicates cerebral is-chemia, then with a ratio between arterial and venous bloodvolumes of 25:75 contributing to the SrcO2 signal dis-played on the monitor, as most NIRS devices adopt, we cancalculate which readings actually indicate cerebral is-chemia and which readings may assure us that this is notthe case [8]. In detail, if the SaO2 is 95 % and SjbO2 50 %,the resulting SrcO2 should be 61 %, which can be con-sidered as ‘‘normal’’. Thus with a standard deviation of5 % a SrcO2 measurement should be below 52 % (61-1.96 9 5 %) to be more than 95 % certain that the tissue isactually ischemic and above 71 % (61 ? 1.96 9 5 %) tobe certain that it is not, implying a large ‘‘grey zone’’ ofSrcO2 values where its diagnostic ability is inconclusive[13]. On the other hand, changing of the body position (e.g.head-up or head-down tilting) may change the ratio be-tween arterial and venous blood volumes of 25:75, so thatfor instance decreases in the SrcO2 readings are simply theresults of an increased proportion of venous blood con-tributing to the signal, rather than a true change in cerebraltissue oxygenation. In this respect, the higher SrcO2 valuesafter raising patients to the sitting position during desflu-rane anesthesia in the abovementioned study [10] could beinterpreted as evidence for cerebral arterial vasodilationunder desflurane and maintained cerebrovascular tone un-der propofol anesthesia.In conclusion, until a standardization of NIRS deviceshas been effectuated, the clinical context may influence thechoice of the adequate NIRS device for a specific purpose.Open Access This article is distributed under the terms of theCreative Commons Attribution License which permits any use, dis-tribution, and reproduction in any medium, provided the originalauthor(s) and the source are credited.References1. Scheeren TW, Schober P, Schwarte LA. Monitoring tissue oxy-genation by near infrared spectroscopy (NIRS): background andJ Clin Monit Comput (2015) 29:217–220 219123current applications. J Clin Monit Comput. 2012;26(4):279–87.doi:10.1007/s10877-012-9348-y.2. Kenosi M, Naulaers G, Ryan C, Dempsey E. Current researchsuggests that the future looks brighter for cerebral oxygenationmonitoring in preterm infants. Acta Paediatr. 2015;104(3):225–31. doi:10.1111/apa.12906.3. van Beest PA, Vos JJ, Poterman M, Kalmar AF, Scheeren TW.Tissue oxygenation as a target for goal-directed therapy in high-risk surgery: a pilot study. BMC Anesthesiol. 2014;14:122.doi:10.1186/1471-2253-14-122.4. van Beest PA, Scheeren TW. Tissue oxygen saturation as a goal,but when and where should we measure it? J Clin Monit Comput.2013;27(3):211–3. doi:10.1007/s10877-013-9438-5.5. Smith RS, Murkin JM. A novel assessment of peripheral tissuemicrocirculatory vasoreactivity using vascular occlusion testingduring cardiopulmonary bypass. J Cardiothorac Vasc Anesth.2014;28(5):1217–20. doi:10.1053/j.jvca.2014.03.016.6. Nygren A, Rennerfelt K, Zhang Q. Detection of changes inmuscle oxygen saturation in the human leg: a comparison of twonear-infrared spectroscopy devices. J Clin Monit Comput.2014;28(1):57–62. doi:10.1007/s10877-013-9494-x.7. Spruit RJ, Schwarte LA, Hakenberg OW, Scheeren TW. Asso-ciation of intraoperative tissue oxygenation with suspected riskfactors for tissue hypoxia. J Clin Monit Comput. 2013;27(5):541–50. doi:10.1007/s10877-013-9460-7.8. Hyttel-Sorensen S, Hessel TW, Greisen G. Peripheral tissueoximetry: comparing three commercial near-infrared spectroscopyoximeters on the forearm. J Clin Monit Comput. 2014;28(2):149–55. doi:10.1007/s10877-013-9507-9.9. Davie SN, Grocott HP. Impact of extracranial contamination onregional cerebral oxygen saturation: a comparison of three cere-bral oximetry technologies. Anesthesiology. 2012;116(4):834–40. doi:10.1097/ALN.0b013e31824c00d7.10. Kim JY, Lee JS, Lee KC, Kim HS, Kim SH, Kwak HJ. The effectof desflurane versus propofol on regional cerebral oxygenation inthe sitting position for shoulder arthroscopy. J Clin MonitComput. 2014;28(4):371–6. doi:10.1007/s10877-013-9543-5.11. Strebel S, Lam AM, Matta B, Mayberg TS, Aaslid R, NewellDW. Dynamic and static cerebral autoregulation during isoflu-rane, desflurane, and propofol anesthesia. Anesthesiology.1995;83(1):66–76.12. Van Noord BA, Stalker CL, Roffey P, Thangathurai D. The useof regional cerebral oximetry monitoring during controlled hy-potension: a case series. J Clin Monit Comput. 2014;28(3):319–23. doi:10.1007/s10877-013-9523-9.13. Ray P, Le Manach Y, Riou B, Houle TT. Statistical evaluation ofa biomarker. Anesthesiology. 2010;112(4):1023–40. doi:10.1097/ALN.0b013e3181d47604.220 J Clin Monit Comput (2015) 29:217–220123

Proceedings - University of Groningen

   University of GroningenJournal of clinical monitoring and computing 2014 end of year summaryScheeren, Thomas W. L.; Bendjelid, KarimPublished in:Journal of clinical monitoring and computingDOI:10.1007/s10877-015-9689-4IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2015Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Scheeren, T. W. L., & Bendjelid, K. (2015). Journal of clinical monitoring and computing 2014 end of yearsummary: near infrared spectroscopy (NIRS). Journal of clinical monitoring and computing, 29(2), 217-220.https://doi.org/10.1007/s10877-015-9689-4CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 31-10-2023REVIEW PAPERJournal of clinical monitoring and computing 2014 end of yearsummary: near infrared spectroscopy (NIRS)Thomas W. L. Scheeren1,3 • Karim Bendjelid2Received: 13 February 2015 / Accepted: 13 February 2015 / Published online: 26 March 2015 The Author(s) 2015. This article is published with open access at Springerlink.comNear infrared spectroscopy (NIRS) is a non-invasivemethod for monitoring hemoglobin oxygen saturationwithin the microvessels. It is therefore also sometimes(erroneously) referred to as a measure of tissue oxygena-tion. By using self-adhesive optodes on the body surface,measurements can be taken in tissues below the skin up to adepth of 3–4 cm. The near infrared light (unlike visiblelight) even penetrates bone tissue, allowing measurementof regional cerebral oxygenation (SrcO2). There are nu-merous devices using NIRS technology available on themarket, and the main applications for use includemonitoring of SrcO2 during cardiothoracic and vascular(particularly carotid artery) surgery, as well as non-cardiacsurgery that is performed in the sitting or so-called beachchair position [1]. Another widespread use is the assess-ment of SrcO2 in neonates and preterm infants [2]. Fur-thermore, there have been attempts to use peripheral tissueoxygenation (SptO2) measurements by NIRS for guidingtherapy and predicting outcome in emergency medicine(both pre-hospital and emergency room use) and in theperioperative setting [3]. Finally, the ability to measureSptO2 at different sites [4] raised interest in researchers tolook at physiological changes, e.g. during exercise, inmusculature of the leg or arm. For this, a specialprovocation test (the vascular occlusion test (VOT) by in-flating a tourniquet proximal to the measurement site) hasbeen developed. The VOT looks at the rate of deoxy-genation during ischemia (vascular occlusion), which isconsidered as a measure of muscle and mitochondrialoxygen consumption, and at the rate of reoxygenationduring reperfusion, reflecting the reactivity of the micro-circulation [5].The Journal of Clinical Monitoring and Computing(JCMC) has become an ideal platform for publishingNIRS-related research, as reflected by an increasing num-ber of articles published in the recent years. This articlewill review two papers on peripheral (SptO2) and two pa-pers on cerebral hemoglobin oxygen saturation (SrcO2)published last year in the JCMC.1 NIRS for measuring peripheral hemoglobinoxygen saturationThe first two articles focus on a comparison of differentdevices measuring SptO2. Why is that an issue at all? Let’sgo back in time: Twenty years ago, with the first appear-ance of pulse oximeters in clinical use to measure periph-eral arterial oxygen saturation (SaO2), there were severalcompanies that developed and marketed such devices,which in turn incorporated different technologies (regard-ing wavelength used, measurement site etc.). As a conse-quence, at that time SaO2 had to be interpreted in view ofthe device used, and their readings could differ by severalpercentage points in individual patients. Nowadays, afterstandardization and technical progress of pulse oximetertechnologies, no one cares any longer with what device agiven SaO2 is measured, since variation between differentvendors has become negligible. With NIRS technology,& Thomas W. L. Scheerent.w.l.scheeren@umcg.nl1 Department of Anaesthesiology, University Medical CenterGroningen, Groningen, The Netherlands2 Department of Anaesthesiology and Intensive Care, IntensiveCare Service, Geneva University Hospitals, University ofGeneva, Geneva, Switzerland3 Department of Anaesthesiology, University of Groningen,Groningen, The Netherlands123J Clin Monit Comput (2015) 29:217–220DOI 10.1007/s10877-015-9689-4this standardisation process has still to be initiated, and weare currently confronted with a huge variety of devicesmeasuring regional hemoglobin oxygen saturation by using(one to four) different wavelengths, and come with multi-ple shaped optodes or sensors intended to be used at dif-ferent anatomic regions (forehead, thenar eminence,somatic organs, muscle etc.). This creates an area ofvalidation research of different NIRS applications, twoexamples of which are summarized in the followingchapter.The first study compares the use of two NIRS devices onSptO2 on the leg muscles of healthy human volunteers, withand without performing exercise [6]. Of note, only one ofthese devices (the InSpectra, Hutchinson Technologies) isproposed for this application, while the other one (the Invos4100, Somanetics) is primarily used for measuring SrcO2.Consequently, due to these different applications, the au-thors found a significant difference in muscle hemoglobinoxygen saturation of slightly more than 10 % already atbaseline (resting conditions), with the InSpectra showing thehigher values (87 ± 8 vs. 76 ± 6 %). The former was inclose agreement with baseline values (86 ± 6 %) observedwith the same device in 160 patients under general anaes-thesia [7]. During exercise, muscle hemoglobin oxygensaturation decreased immediately with both devices, tovalues close to zero (InSpectra) or slightly above 20 %(Invos) [6]. This decrease was reversible after cessation ofexercise, with slight hyperaemia of 8 % (InSpectra) and18 % above baseline values (Invos), respectively. The au-thors also performed a vascular occlusion test, which re-vealed similar results as the exercise test. Finally, theylooked at the influence of skin and subcutaneous tissuethickness as assessed by ultrasound on the measurements ofboth devices and found that the InSpectra, but not the Invos,was prone to increased skin and subcutaneous tissue thick-ness as reflected by lower SptO2 values. Since the measuringdepth within a tissue is determined by the distance betweenthe light-emitting and light-detecting part of the optode, thesmaller distance within the InSpectra sensor (30 mm ascompared to 40 mm in the Invos sensor) might explain itshigher susceptibility to thicker skin and subcutaneous tissue.The authors conclude that the Invos, although not primarilydesigned for this purpose, can be used to detect ex-perimentally and exercise induced skeletal muscle ischemiain the human leg, interchangeable with the InSpectra in thisrespect [6]. However, the study confirms the abovemen-tioned differences in sensitivity or calibration between NIRSdevices to detect changes in regional hemoglobin oxygensaturation.In the second study looking at peripheral hemoglobinoxygen saturation the authors compared the ability of threeNIRS devices (Invos 5100C, Nonin Equanox 7600, andFore-Sight, CASMed), all of which are primarily marketedfor cerebral and somatic use, to measure SptO2 on theforearm muscles of healthy human volunteers. [8] Themedian readings of the three devices at baseline werewithin 6 % points, with Invos giving the highest and Fore-Sight the lowest steady state values. To test the repeata-bility of the measurements the sensors were repositioned20 times on the forearm during hemodynamic steady stateconditions. The repeatability of Fore-Sight was best, whilethat of Equanox was worst, with no difference betweensame-site and various-site repeatability. Also, the authorsrepeatedly performed a VOT to induce maximal tissuedeoxygenation and to evaluate the dynamic properties ofthe three NIRS devices. The slopes of desaturation weresteepest with Equanox. Furthermore, Equanox and Invosoften reached their lower boundary values during ischemiaat a level of 20–30 % while Fore-Sight showed continuingdesaturation, likely best representing truly changing oxy-genation. This difference in dynamics found in SptO2measurements on the arm might also apply to measure-ments on the forehead, suggesting that differences in so-called removal of extra-cranial tissue contamination aspresented in a recent study [9] could be simply a matter ofdifferent sensitivity of NIRS devices to overall oxygena-tion changes in the tissue, as elegantly discussed by theauthors. The study has several clinical implications andconsequences when it comes to choosing a particular NIRSdevice: when NIRS oximetry is intended to be used fortrend monitoring, the repeatability of measurement is lessimportant. If in addition the sensitivity of a NIRS device tochanges in hemoglobin oxygen saturation is low, the risk ofundetected true hypoxia will be high. However, if NIRS isto be used as a spot measurement (e.g. in the emergencyroom) or if the monitoring is started when the patient statusis uncertain (e.g. in the ICU or OR in a deteriorating patientwithout having a baseline value), a good repeatability ofmeasurement or a close proximity to absolute (true) valuesbecomes more important. Since high sensitivity comes atthe expense of good repeatability, a pragmatic approachwould be to care less about the closeness to the ‘true’values, but to settle for the device with the best combina-tion of repeatability and sensitivity to changing oxygena-tion [8].2 NIRS for measuring cerebral hemoglobinoxygen saturationThe most commonly used application for NIRS technologyis monitoring cerebral hemoglobin oxygen saturation(SrcO2). A recently developed use includes patients un-dergoing arthroscopic shoulder surgery in the sitting posi-tion, which is preferred in some centers despite the dangerof hemodynamic instability for the sake of better surgical218 J Clin Monit Comput (2015) 29:217–220123conditions. Although it is known that SrcO2 is lower underthose conditions as compared to the alternative lateral de-cubitus position, the clinical relevant question arises whe-ther intravenous anesthesia or inhalational anesthesia issuperior when it comes to preserving cerebral oxygenation.This question was investigated in a recent trial, in which 40patients were randomized to receive either propofol ordesflurane, both titrated to similar anesthetic depth as ob-tained by bispectral index (BIS), resulting also in similarhemodynamics [10]. While SrcO2 significantly decreasedin both groups in the first minutes after patients were lo-cated from the supine to the sitting position, values re-mained significantly higher in the desflurane group ascompared to the propofol group, despite lower bloodpressures. Furthermore, cerebral desaturations, defined asSrcO2 below 75 % of individual baseline values, occurredin two patients of the propofol group but in none of thedesflurane group. Unfortunately, measurements werestopped 9 min after positioning of the patients, preventingconclusions on the intraoperative course of SrcO2 as wellas on-going differences between anesthetic agents. Theauthors conclude that desflurane preserved cerebral oxy-genation better than propofol at equipotent anestheticconcentrations [10]. These observations are surprising atfirst sight, since it is long known that volatile anestheticsimpair autoregulation of cerebral blood flow more thanpropofol [11]. The authors speculate that desflurane (unlikepropofol) induced cerebral vasodilation and thus increasedcerebral blood flow (CBF), which in turn compensates thereduction in CBF following installation of the sitting po-sition. Otherwise, we may also speculate that the negativeimpact of propofol on venous return and thus cardiacoutput is huge in the present posture due to the venodilatoreffect of the drug.Another example of the clinical applicability of NIRStechnology to measure SrcO2 is presented in a case seriesof 20 patients undergoing major abdominal or urologicalsurgery under general anaesthesia [12]. The authors usedcontrolled hypotension induced by nitroglycerin (NTG) inorder to minimize blood loss and optimise surgical condi-tions. Vasodilation with NTG reduced MAP by about 20 %(from 90 ± 14 to 72 ± 14 mmHg), whereas it increasedSrcO2 in all patients by an average between 15 and 21 %.Although the authors did not measure blood flow (e.g.cardiac output) and did not report what NIRS device theyused, these findings demonstrate that blood pressure andtissue perfusion are not always related in a linear, positivefashion (uncoupling phenomenon). The authors discuss asa potential confounder that the volatile anaesthetics usedmight have led to luxury perfusion of the monitored brainarea while diverting blood away from potentially ischemicregions. [12] Nevertheless, this case series shows thatNIRS monitoring can be used to ensure the adequacy oftissue oxygenation during controlled hypotension and ex-pands the scope of conventional hemodynamic monitoringin this respect. This way it may contribute to improvepatient’s safety in case of macro-microcirculatorydecoupling.3 Interpretation of SrcO2 valuesSince there is no consensus about what should be consid-ered ‘‘normal values’’ for cerebral hemoglobin oxygensaturation, the authors of the previous study [8] come upwith a very interesting calculation: Assuming that a jugularbulb saturation (SjbO2, the gold standard for assessingcerebral hypoxemia) below 50 % indicates cerebral is-chemia, then with a ratio between arterial and venous bloodvolumes of 25:75 contributing to the SrcO2 signal dis-played on the monitor, as most NIRS devices adopt, we cancalculate which readings actually indicate cerebral is-chemia and which readings may assure us that this is notthe case [8]. In detail, if the SaO2 is 95 % and SjbO2 50 %,the resulting SrcO2 should be 61 %, which can be con-sidered as ‘‘normal’’. Thus with a standard deviation of5 % a SrcO2 measurement should be below 52 % (61-1.96 9 5 %) to be more than 95 % certain that the tissue isactually ischemic and above 71 % (61 ? 1.96 9 5 %) tobe certain that it is not, implying a large ‘‘grey zone’’ ofSrcO2 values where its diagnostic ability is inconclusive[13]. On the other hand, changing of the body position (e.g.head-up or head-down tilting) may change the ratio be-tween arterial and venous blood volumes of 25:75, so thatfor instance decreases in the SrcO2 readings are simply theresults of an increased proportion of venous blood con-tributing to the signal, rather than a true change in cerebraltissue oxygenation. In this respect, the higher SrcO2 valuesafter raising patients to the sitting position during desflu-rane anesthesia in the abovementioned study [10] could beinterpreted as evidence for cerebral arterial vasodilationunder desflurane and maintained cerebrovascular tone un-der propofol anesthesia.In conclusion, until a standardization of NIRS deviceshas been effectuated, the clinical context may influence thechoice of the adequate NIRS device for a specific purpose.Open Access This article is distributed under the terms of theCreative Commons Attribution License which permits any use, dis-tribution, and reproduction in any medium, provided the originalauthor(s) and the source are credited.References1. Scheeren TW, Schober P, Schwarte LA. Monitoring tissue oxy-genation by near infrared spectroscopy (NIRS): background andJ Clin Monit Comput (2015) 29:217–220 219123current applications. J Clin Monit Comput. 2012;26(4):279–87.doi:10.1007/s10877-012-9348-y.2. Kenosi M, Naulaers G, Ryan C, Dempsey E. Current researchsuggests that the future looks brighter for cerebral oxygenationmonitoring in preterm infants. Acta Paediatr. 2015;104(3):225–31. doi:10.1111/apa.12906.3. van Beest PA, Vos JJ, Poterman M, Kalmar AF, Scheeren TW.Tissue oxygenation as a target for goal-directed therapy in high-risk surgery: a pilot study. BMC Anesthesiol. 2014;14:122.doi:10.1186/1471-2253-14-122.4. van Beest PA, Scheeren TW. Tissue oxygen saturation as a goal,but when and where should we measure it? J Clin Monit Comput.2013;27(3):211–3. doi:10.1007/s10877-013-9438-5.5. Smith RS, Murkin JM. A novel assessment of peripheral tissuemicrocirculatory vasoreactivity using vascular occlusion testingduring cardiopulmonary bypass. J Cardiothorac Vasc Anesth.2014;28(5):1217–20. doi:10.1053/j.jvca.2014.03.016.6. Nygren A, Rennerfelt K, Zhang Q. Detection of changes inmuscle oxygen saturation in the human leg: a comparison of twonear-infrared spectroscopy devices. J Clin Monit Comput.2014;28(1):57–62. doi:10.1007/s10877-013-9494-x.7. Spruit RJ, Schwarte LA, Hakenberg OW, Scheeren TW. Asso-ciation of intraoperative tissue oxygenation with suspected riskfactors for tissue hypoxia. J Clin Monit Comput. 2013;27(5):541–50. doi:10.1007/s10877-013-9460-7.8. Hyttel-Sorensen S, Hessel TW, Greisen G. Peripheral tissueoximetry: comparing three commercial near-infrared spectroscopyoximeters on the forearm. J Clin Monit Comput. 2014;28(2):149–55. doi:10.1007/s10877-013-9507-9.9. Davie SN, Grocott HP. Impact of extracranial contamination onregional cerebral oxygen saturation: a comparison of three cere-bral oximetry technologies. Anesthesiology. 2012;116(4):834–40. doi:10.1097/ALN.0b013e31824c00d7.10. Kim JY, Lee JS, Lee KC, Kim HS, Kim SH, Kwak HJ. The effectof desflurane versus propofol on regional cerebral oxygenation inthe sitting position for shoulder arthroscopy. J Clin MonitComput. 2014;28(4):371–6. doi:10.1007/s10877-013-9543-5.11. Strebel S, Lam AM, Matta B, Mayberg TS, Aaslid R, NewellDW. Dynamic and static cerebral autoregulation during isoflu-rane, desflurane, and propofol anesthesia. Anesthesiology.1995;83(1):66–76.12. Van Noord BA, Stalker CL, Roffey P, Thangathurai D. The useof regional cerebral oximetry monitoring during controlled hy-potension: a case series. J Clin Monit Comput. 2014;28(3):319–23. doi:10.1007/s10877-013-9523-9.13. Ray P, Le Manach Y, Riou B, Houle TT. Statistical evaluation ofa biomarker. Anesthesiology. 2010;112(4):1023–40. doi:10.1097/ALN.0b013e3181d47604.220 J Clin Monit Comput (2015) 29:217–220123

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Journal of clinical monitoring and computing 2014 end of year summary: near infrared spectroscopy (NIRS)

   University of GroningenJournal of clinical monitoring and computing 2014 end of year summaryScheeren, Thomas W. L.; Bendjelid, KarimPublished in:Journal of clinical monitoring and computingDOI:10.1007/s10877-015-9689-4IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2015Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Scheeren, T. W. L., & Bendjelid, K. (2015). Journal of clinical monitoring and computing 2014 end of yearsummary: near infrared spectroscopy (NIRS). Journal of clinical monitoring and computing, 29(2), 217-220.https://doi.org/10.1007/s10877-015-9689-4CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 30-10-2023REVIEW PAPERJournal of clinical monitoring and computing 2014 end of yearsummary: near infrared spectroscopy (NIRS)Thomas W. L. Scheeren1,3 • Karim Bendjelid2Received: 13 February 2015 / Accepted: 13 February 2015 / Published online: 26 March 2015 The Author(s) 2015. This article is published with open access at Springerlink.comNear infrared spectroscopy (NIRS) is a non-invasivemethod for monitoring hemoglobin oxygen saturationwithin the microvessels. It is therefore also sometimes(erroneously) referred to as a measure of tissue oxygena-tion. By using self-adhesive optodes on the body surface,measurements can be taken in tissues below the skin up to adepth of 3–4 cm. The near infrared light (unlike visiblelight) even penetrates bone tissue, allowing measurementof regional cerebral oxygenation (SrcO2). There are nu-merous devices using NIRS technology available on themarket, and the main applications for use includemonitoring of SrcO2 during cardiothoracic and vascular(particularly carotid artery) surgery, as well as non-cardiacsurgery that is performed in the sitting or so-called beachchair position [1]. Another widespread use is the assess-ment of SrcO2 in neonates and preterm infants [2]. Fur-thermore, there have been attempts to use peripheral tissueoxygenation (SptO2) measurements by NIRS for guidingtherapy and predicting outcome in emergency medicine(both pre-hospital and emergency room use) and in theperioperative setting [3]. Finally, the ability to measureSptO2 at different sites [4] raised interest in researchers tolook at physiological changes, e.g. during exercise, inmusculature of the leg or arm. For this, a specialprovocation test (the vascular occlusion test (VOT) by in-flating a tourniquet proximal to the measurement site) hasbeen developed. The VOT looks at the rate of deoxy-genation during ischemia (vascular occlusion), which isconsidered as a measure of muscle and mitochondrialoxygen consumption, and at the rate of reoxygenationduring reperfusion, reflecting the reactivity of the micro-circulation [5].The Journal of Clinical Monitoring and Computing(JCMC) has become an ideal platform for publishingNIRS-related research, as reflected by an increasing num-ber of articles published in the recent years. This articlewill review two papers on peripheral (SptO2) and two pa-pers on cerebral hemoglobin oxygen saturation (SrcO2)published last year in the JCMC.1 NIRS for measuring peripheral hemoglobinoxygen saturationThe first two articles focus on a comparison of differentdevices measuring SptO2. Why is that an issue at all? Let’sgo back in time: Twenty years ago, with the first appear-ance of pulse oximeters in clinical use to measure periph-eral arterial oxygen saturation (SaO2), there were severalcompanies that developed and marketed such devices,which in turn incorporated different technologies (regard-ing wavelength used, measurement site etc.). As a conse-quence, at that time SaO2 had to be interpreted in view ofthe device used, and their readings could differ by severalpercentage points in individual patients. Nowadays, afterstandardization and technical progress of pulse oximetertechnologies, no one cares any longer with what device agiven SaO2 is measured, since variation between differentvendors has become negligible. With NIRS technology,& Thomas W. L. Scheerent.w.l.scheeren@umcg.nl1 Department of Anaesthesiology, University Medical CenterGroningen, Groningen, The Netherlands2 Department of Anaesthesiology and Intensive Care, IntensiveCare Service, Geneva University Hospitals, University ofGeneva, Geneva, Switzerland3 Department of Anaesthesiology, University of Groningen,Groningen, The Netherlands123J Clin Monit Comput (2015) 29:217–220DOI 10.1007/s10877-015-9689-4this standardisation process has still to be initiated, and weare currently confronted with a huge variety of devicesmeasuring regional hemoglobin oxygen saturation by using(one to four) different wavelengths, and come with multi-ple shaped optodes or sensors intended to be used at dif-ferent anatomic regions (forehead, thenar eminence,somatic organs, muscle etc.). This creates an area ofvalidation research of different NIRS applications, twoexamples of which are summarized in the followingchapter.The first study compares the use of two NIRS devices onSptO2 on the leg muscles of healthy human volunteers, withand without performing exercise [6]. Of note, only one ofthese devices (the InSpectra, Hutchinson Technologies) isproposed for this application, while the other one (the Invos4100, Somanetics) is primarily used for measuring SrcO2.Consequently, due to these different applications, the au-thors found a significant difference in muscle hemoglobinoxygen saturation of slightly more than 10 % already atbaseline (resting conditions), with the InSpectra showing thehigher values (87 ± 8 vs. 76 ± 6 %). The former was inclose agreement with baseline values (86 ± 6 %) observedwith the same device in 160 patients under general anaes-thesia [7]. During exercise, muscle hemoglobin oxygensaturation decreased immediately with both devices, tovalues close to zero (InSpectra) or slightly above 20 %(Invos) [6]. This decrease was reversible after cessation ofexercise, with slight hyperaemia of 8 % (InSpectra) and18 % above baseline values (Invos), respectively. The au-thors also performed a vascular occlusion test, which re-vealed similar results as the exercise test. Finally, theylooked at the influence of skin and subcutaneous tissuethickness as assessed by ultrasound on the measurements ofboth devices and found that the InSpectra, but not the Invos,was prone to increased skin and subcutaneous tissue thick-ness as reflected by lower SptO2 values. Since the measuringdepth within a tissue is determined by the distance betweenthe light-emitting and light-detecting part of the optode, thesmaller distance within the InSpectra sensor (30 mm ascompared to 40 mm in the Invos sensor) might explain itshigher susceptibility to thicker skin and subcutaneous tissue.The authors conclude that the Invos, although not primarilydesigned for this purpose, can be used to detect ex-perimentally and exercise induced skeletal muscle ischemiain the human leg, interchangeable with the InSpectra in thisrespect [6]. However, the study confirms the abovemen-tioned differences in sensitivity or calibration between NIRSdevices to detect changes in regional hemoglobin oxygensaturation.In the second study looking at peripheral hemoglobinoxygen saturation the authors compared the ability of threeNIRS devices (Invos 5100C, Nonin Equanox 7600, andFore-Sight, CASMed), all of which are primarily marketedfor cerebral and somatic use, to measure SptO2 on theforearm muscles of healthy human volunteers. [8] Themedian readings of the three devices at baseline werewithin 6 % points, with Invos giving the highest and Fore-Sight the lowest steady state values. To test the repeata-bility of the measurements the sensors were repositioned20 times on the forearm during hemodynamic steady stateconditions. The repeatability of Fore-Sight was best, whilethat of Equanox was worst, with no difference betweensame-site and various-site repeatability. Also, the authorsrepeatedly performed a VOT to induce maximal tissuedeoxygenation and to evaluate the dynamic properties ofthe three NIRS devices. The slopes of desaturation weresteepest with Equanox. Furthermore, Equanox and Invosoften reached their lower boundary values during ischemiaat a level of 20–30 % while Fore-Sight showed continuingdesaturation, likely best representing truly changing oxy-genation. This difference in dynamics found in SptO2measurements on the arm might also apply to measure-ments on the forehead, suggesting that differences in so-called removal of extra-cranial tissue contamination aspresented in a recent study [9] could be simply a matter ofdifferent sensitivity of NIRS devices to overall oxygena-tion changes in the tissue, as elegantly discussed by theauthors. The study has several clinical implications andconsequences when it comes to choosing a particular NIRSdevice: when NIRS oximetry is intended to be used fortrend monitoring, the repeatability of measurement is lessimportant. If in addition the sensitivity of a NIRS device tochanges in hemoglobin oxygen saturation is low, the risk ofundetected true hypoxia will be high. However, if NIRS isto be used as a spot measurement (e.g. in the emergencyroom) or if the monitoring is started when the patient statusis uncertain (e.g. in the ICU or OR in a deteriorating patientwithout having a baseline value), a good repeatability ofmeasurement or a close proximity to absolute (true) valuesbecomes more important. Since high sensitivity comes atthe expense of good repeatability, a pragmatic approachwould be to care less about the closeness to the ‘true’values, but to settle for the device with the best combina-tion of repeatability and sensitivity to changing oxygena-tion [8].2 NIRS for measuring cerebral hemoglobinoxygen saturationThe most commonly used application for NIRS technologyis monitoring cerebral hemoglobin oxygen saturation(SrcO2). A recently developed use includes patients un-dergoing arthroscopic shoulder surgery in the sitting posi-tion, which is preferred in some centers despite the dangerof hemodynamic instability for the sake of better surgical218 J Clin Monit Comput (2015) 29:217–220123conditions. Although it is known that SrcO2 is lower underthose conditions as compared to the alternative lateral de-cubitus position, the clinical relevant question arises whe-ther intravenous anesthesia or inhalational anesthesia issuperior when it comes to preserving cerebral oxygenation.This question was investigated in a recent trial, in which 40patients were randomized to receive either propofol ordesflurane, both titrated to similar anesthetic depth as ob-tained by bispectral index (BIS), resulting also in similarhemodynamics [10]. While SrcO2 significantly decreasedin both groups in the first minutes after patients were lo-cated from the supine to the sitting position, values re-mained significantly higher in the desflurane group ascompared to the propofol group, despite lower bloodpressures. Furthermore, cerebral desaturations, defined asSrcO2 below 75 % of individual baseline values, occurredin two patients of the propofol group but in none of thedesflurane group. Unfortunately, measurements werestopped 9 min after positioning of the patients, preventingconclusions on the intraoperative course of SrcO2 as wellas on-going differences between anesthetic agents. Theauthors conclude that desflurane preserved cerebral oxy-genation better than propofol at equipotent anestheticconcentrations [10]. These observations are surprising atfirst sight, since it is long known that volatile anestheticsimpair autoregulation of cerebral blood flow more thanpropofol [11]. The authors speculate that desflurane (unlikepropofol) induced cerebral vasodilation and thus increasedcerebral blood flow (CBF), which in turn compensates thereduction in CBF following installation of the sitting po-sition. Otherwise, we may also speculate that the negativeimpact of propofol on venous return and thus cardiacoutput is huge in the present posture due to the venodilatoreffect of the drug.Another example of the clinical applicability of NIRStechnology to measure SrcO2 is presented in a case seriesof 20 patients undergoing major abdominal or urologicalsurgery under general anaesthesia [12]. The authors usedcontrolled hypotension induced by nitroglycerin (NTG) inorder to minimize blood loss and optimise surgical condi-tions. Vasodilation with NTG reduced MAP by about 20 %(from 90 ± 14 to 72 ± 14 mmHg), whereas it increasedSrcO2 in all patients by an average between 15 and 21 %.Although the authors did not measure blood flow (e.g.cardiac output) and did not report what NIRS device theyused, these findings demonstrate that blood pressure andtissue perfusion are not always related in a linear, positivefashion (uncoupling phenomenon). The authors discuss asa potential confounder that the volatile anaesthetics usedmight have led to luxury perfusion of the monitored brainarea while diverting blood away from potentially ischemicregions. [12] Nevertheless, this case series shows thatNIRS monitoring can be used to ensure the adequacy oftissue oxygenation during controlled hypotension and ex-pands the scope of conventional hemodynamic monitoringin this respect. This way it may contribute to improvepatient’s safety in case of macro-microcirculatorydecoupling.3 Interpretation of SrcO2 valuesSince there is no consensus about what should be consid-ered ‘‘normal values’’ for cerebral hemoglobin oxygensaturation, the authors of the previous study [8] come upwith a very interesting calculation: Assuming that a jugularbulb saturation (SjbO2, the gold standard for assessingcerebral hypoxemia) below 50 % indicates cerebral is-chemia, then with a ratio between arterial and venous bloodvolumes of 25:75 contributing to the SrcO2 signal dis-played on the monitor, as most NIRS devices adopt, we cancalculate which readings actually indicate cerebral is-chemia and which readings may assure us that this is notthe case [8]. In detail, if the SaO2 is 95 % and SjbO2 50 %,the resulting SrcO2 should be 61 %, which can be con-sidered as ‘‘normal’’. Thus with a standard deviation of5 % a SrcO2 measurement should be below 52 % (61-1.96 9 5 %) to be more than 95 % certain that the tissue isactually ischemic and above 71 % (61 ? 1.96 9 5 %) tobe certain that it is not, implying a large ‘‘grey zone’’ ofSrcO2 values where its diagnostic ability is inconclusive[13]. On the other hand, changing of the body position (e.g.head-up or head-down tilting) may change the ratio be-tween arterial and venous blood volumes of 25:75, so thatfor instance decreases in the SrcO2 readings are simply theresults of an increased proportion of venous blood con-tributing to the signal, rather than a true change in cerebraltissue oxygenation. In this respect, the higher SrcO2 valuesafter raising patients to the sitting position during desflu-rane anesthesia in the abovementioned study [10] could beinterpreted as evidence for cerebral arterial vasodilationunder desflurane and maintained cerebrovascular tone un-der propofol anesthesia.In conclusion, until a standardization of NIRS deviceshas been effectuated, the clinical context may influence thechoice of the adequate NIRS device for a specific purpose.Open Access This article is distributed under the terms of theCreative Commons Attribution License which permits any use, dis-tribution, and reproduction in any medium, provided the originalauthor(s) and the source are credited.References1. Scheeren TW, Schober P, Schwarte LA. Monitoring tissue oxy-genation by near infrared spectroscopy (NIRS): background andJ Clin Monit Comput (2015) 29:217–220 219123current applications. J Clin Monit Comput. 2012;26(4):279–87.doi:10.1007/s10877-012-9348-y.2. Kenosi M, Naulaers G, Ryan C, Dempsey E. Current researchsuggests that the future looks brighter for cerebral oxygenationmonitoring in preterm infants. Acta Paediatr. 2015;104(3):225–31. doi:10.1111/apa.12906.3. van Beest PA, Vos JJ, Poterman M, Kalmar AF, Scheeren TW.Tissue oxygenation as a target for goal-directed therapy in high-risk surgery: a pilot study. BMC Anesthesiol. 2014;14:122.doi:10.1186/1471-2253-14-122.4. van Beest PA, Scheeren TW. Tissue oxygen saturation as a goal,but when and where should we measure it? J Clin Monit Comput.2013;27(3):211–3. doi:10.1007/s10877-013-9438-5.5. Smith RS, Murkin JM. A novel assessment of peripheral tissuemicrocirculatory vasoreactivity using vascular occlusion testingduring cardiopulmonary bypass. J Cardiothorac Vasc Anesth.2014;28(5):1217–20. doi:10.1053/j.jvca.2014.03.016.6. Nygren A, Rennerfelt K, Zhang Q. Detection of changes inmuscle oxygen saturation in the human leg: a comparison of twonear-infrared spectroscopy devices. J Clin Monit Comput.2014;28(1):57–62. doi:10.1007/s10877-013-9494-x.7. Spruit RJ, Schwarte LA, Hakenberg OW, Scheeren TW. Asso-ciation of intraoperative tissue oxygenation with suspected riskfactors for tissue hypoxia. J Clin Monit Comput. 2013;27(5):541–50. doi:10.1007/s10877-013-9460-7.8. Hyttel-Sorensen S, Hessel TW, Greisen G. Peripheral tissueoximetry: comparing three commercial near-infrared spectroscopyoximeters on the forearm. J Clin Monit Comput. 2014;28(2):149–55. doi:10.1007/s10877-013-9507-9.9. Davie SN, Grocott HP. Impact of extracranial contamination onregional cerebral oxygen saturation: a comparison of three cere-bral oximetry technologies. Anesthesiology. 2012;116(4):834–40. doi:10.1097/ALN.0b013e31824c00d7.10. Kim JY, Lee JS, Lee KC, Kim HS, Kim SH, Kwak HJ. The effectof desflurane versus propofol on regional cerebral oxygenation inthe sitting position for shoulder arthroscopy. J Clin MonitComput. 2014;28(4):371–6. doi:10.1007/s10877-013-9543-5.11. Strebel S, Lam AM, Matta B, Mayberg TS, Aaslid R, NewellDW. Dynamic and static cerebral autoregulation during isoflu-rane, desflurane, and propofol anesthesia. Anesthesiology.1995;83(1):66–76.12. Van Noord BA, Stalker CL, Roffey P, Thangathurai D. The useof regional cerebral oximetry monitoring during controlled hy-potension: a case series. J Clin Monit Comput. 2014;28(3):319–23. doi:10.1007/s10877-013-9523-9.13. Ray P, Le Manach Y, Riou B, Houle TT. Statistical evaluation ofa biomarker. Anesthesiology. 2010;112(4):1023–40. doi:10.1097/ALN.0b013e3181d47604.220 J Clin Monit Comput (2015) 29:217–220123

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   University of GroningenJournal of clinical monitoring and computing 2014 end of year summaryScheeren, Thomas W. L.; Bendjelid, KarimPublished in:Journal of clinical monitoring and computingDOI:10.1007/s10877-015-9689-4IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2015Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Scheeren, T. W. L., & Bendjelid, K. (2015). Journal of clinical monitoring and computing 2014 end of yearsummary: near infrared spectroscopy (NIRS). Journal of clinical monitoring and computing, 29(2), 217-220.https://doi.org/10.1007/s10877-015-9689-4CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 27-04-2023REVIEW PAPERJournal of clinical monitoring and computing 2014 end of yearsummary: near infrared spectroscopy (NIRS)Thomas W. L. Scheeren1,3 • Karim Bendjelid2Received: 13 February 2015 / Accepted: 13 February 2015 / Published online: 26 March 2015 The Author(s) 2015. This article is published with open access at Springerlink.comNear infrared spectroscopy (NIRS) is a non-invasivemethod for monitoring hemoglobin oxygen saturationwithin the microvessels. It is therefore also sometimes(erroneously) referred to as a measure of tissue oxygena-tion. By using self-adhesive optodes on the body surface,measurements can be taken in tissues below the skin up to adepth of 3–4 cm. The near infrared light (unlike visiblelight) even penetrates bone tissue, allowing measurementof regional cerebral oxygenation (SrcO2). There are nu-merous devices using NIRS technology available on themarket, and the main applications for use includemonitoring of SrcO2 during cardiothoracic and vascular(particularly carotid artery) surgery, as well as non-cardiacsurgery that is performed in the sitting or so-called beachchair position [1]. Another widespread use is the assess-ment of SrcO2 in neonates and preterm infants [2]. Fur-thermore, there have been attempts to use peripheral tissueoxygenation (SptO2) measurements by NIRS for guidingtherapy and predicting outcome in emergency medicine(both pre-hospital and emergency room use) and in theperioperative setting [3]. Finally, the ability to measureSptO2 at different sites [4] raised interest in researchers tolook at physiological changes, e.g. during exercise, inmusculature of the leg or arm. For this, a specialprovocation test (the vascular occlusion test (VOT) by in-flating a tourniquet proximal to the measurement site) hasbeen developed. The VOT looks at the rate of deoxy-genation during ischemia (vascular occlusion), which isconsidered as a measure of muscle and mitochondrialoxygen consumption, and at the rate of reoxygenationduring reperfusion, reflecting the reactivity of the micro-circulation [5].The Journal of Clinical Monitoring and Computing(JCMC) has become an ideal platform for publishingNIRS-related research, as reflected by an increasing num-ber of articles published in the recent years. This articlewill review two papers on peripheral (SptO2) and two pa-pers on cerebral hemoglobin oxygen saturation (SrcO2)published last year in the JCMC.1 NIRS for measuring peripheral hemoglobinoxygen saturationThe first two articles focus on a comparison of differentdevices measuring SptO2. Why is that an issue at all? Let’sgo back in time: Twenty years ago, with the first appear-ance of pulse oximeters in clinical use to measure periph-eral arterial oxygen saturation (SaO2), there were severalcompanies that developed and marketed such devices,which in turn incorporated different technologies (regard-ing wavelength used, measurement site etc.). As a conse-quence, at that time SaO2 had to be interpreted in view ofthe device used, and their readings could differ by severalpercentage points in individual patients. Nowadays, afterstandardization and technical progress of pulse oximetertechnologies, no one cares any longer with what device agiven SaO2 is measured, since variation between differentvendors has become negligible. With NIRS technology,& Thomas W. L. Scheerent.w.l.scheeren@umcg.nl1 Department of Anaesthesiology, University Medical CenterGroningen, Groningen, The Netherlands2 Department of Anaesthesiology and Intensive Care, IntensiveCare Service, Geneva University Hospitals, University ofGeneva, Geneva, Switzerland3 Department of Anaesthesiology, University of Groningen,Groningen, The Netherlands123J Clin Monit Comput (2015) 29:217–220DOI 10.1007/s10877-015-9689-4this standardisation process has still to be initiated, and weare currently confronted with a huge variety of devicesmeasuring regional hemoglobin oxygen saturation by using(one to four) different wavelengths, and come with multi-ple shaped optodes or sensors intended to be used at dif-ferent anatomic regions (forehead, thenar eminence,somatic organs, muscle etc.). This creates an area ofvalidation research of different NIRS applications, twoexamples of which are summarized in the followingchapter.The first study compares the use of two NIRS devices onSptO2 on the leg muscles of healthy human volunteers, withand without performing exercise [6]. Of note, only one ofthese devices (the InSpectra, Hutchinson Technologies) isproposed for this application, while the other one (the Invos4100, Somanetics) is primarily used for measuring SrcO2.Consequently, due to these different applications, the au-thors found a significant difference in muscle hemoglobinoxygen saturation of slightly more than 10 % already atbaseline (resting conditions), with the InSpectra showing thehigher values (87 ± 8 vs. 76 ± 6 %). The former was inclose agreement with baseline values (86 ± 6 %) observedwith the same device in 160 patients under general anaes-thesia [7]. During exercise, muscle hemoglobin oxygensaturation decreased immediately with both devices, tovalues close to zero (InSpectra) or slightly above 20 %(Invos) [6]. This decrease was reversible after cessation ofexercise, with slight hyperaemia of 8 % (InSpectra) and18 % above baseline values (Invos), respectively. The au-thors also performed a vascular occlusion test, which re-vealed similar results as the exercise test. Finally, theylooked at the influence of skin and subcutaneous tissuethickness as assessed by ultrasound on the measurements ofboth devices and found that the InSpectra, but not the Invos,was prone to increased skin and subcutaneous tissue thick-ness as reflected by lower SptO2 values. Since the measuringdepth within a tissue is determined by the distance betweenthe light-emitting and light-detecting part of the optode, thesmaller distance within the InSpectra sensor (30 mm ascompared to 40 mm in the Invos sensor) might explain itshigher susceptibility to thicker skin and subcutaneous tissue.The authors conclude that the Invos, although not primarilydesigned for this purpose, can be used to detect ex-perimentally and exercise induced skeletal muscle ischemiain the human leg, interchangeable with the InSpectra in thisrespect [6]. However, the study confirms the abovemen-tioned differences in sensitivity or calibration between NIRSdevices to detect changes in regional hemoglobin oxygensaturation.In the second study looking at peripheral hemoglobinoxygen saturation the authors compared the ability of threeNIRS devices (Invos 5100C, Nonin Equanox 7600, andFore-Sight, CASMed), all of which are primarily marketedfor cerebral and somatic use, to measure SptO2 on theforearm muscles of healthy human volunteers. [8] Themedian readings of the three devices at baseline werewithin 6 % points, with Invos giving the highest and Fore-Sight the lowest steady state values. To test the repeata-bility of the measurements the sensors were repositioned20 times on the forearm during hemodynamic steady stateconditions. The repeatability of Fore-Sight was best, whilethat of Equanox was worst, with no difference betweensame-site and various-site repeatability. Also, the authorsrepeatedly performed a VOT to induce maximal tissuedeoxygenation and to evaluate the dynamic properties ofthe three NIRS devices. The slopes of desaturation weresteepest with Equanox. Furthermore, Equanox and Invosoften reached their lower boundary values during ischemiaat a level of 20–30 % while Fore-Sight showed continuingdesaturation, likely best representing truly changing oxy-genation. This difference in dynamics found in SptO2measurements on the arm might also apply to measure-ments on the forehead, suggesting that differences in so-called removal of extra-cranial tissue contamination aspresented in a recent study [9] could be simply a matter ofdifferent sensitivity of NIRS devices to overall oxygena-tion changes in the tissue, as elegantly discussed by theauthors. The study has several clinical implications andconsequences when it comes to choosing a particular NIRSdevice: when NIRS oximetry is intended to be used fortrend monitoring, the repeatability of measurement is lessimportant. If in addition the sensitivity of a NIRS device tochanges in hemoglobin oxygen saturation is low, the risk ofundetected true hypoxia will be high. However, if NIRS isto be used as a spot measurement (e.g. in the emergencyroom) or if the monitoring is started when the patient statusis uncertain (e.g. in the ICU or OR in a deteriorating patientwithout having a baseline value), a good repeatability ofmeasurement or a close proximity to absolute (true) valuesbecomes more important. Since high sensitivity comes atthe expense of good repeatability, a pragmatic approachwould be to care less about the closeness to the ‘true’values, but to settle for the device with the best combina-tion of repeatability and sensitivity to changing oxygena-tion [8].2 NIRS for measuring cerebral hemoglobinoxygen saturationThe most commonly used application for NIRS technologyis monitoring cerebral hemoglobin oxygen saturation(SrcO2). A recently developed use includes patients un-dergoing arthroscopic shoulder surgery in the sitting posi-tion, which is preferred in some centers despite the dangerof hemodynamic instability for the sake of better surgical218 J Clin Monit Comput (2015) 29:217–220123conditions. Although it is known that SrcO2 is lower underthose conditions as compared to the alternative lateral de-cubitus position, the clinical relevant question arises whe-ther intravenous anesthesia or inhalational anesthesia issuperior when it comes to preserving cerebral oxygenation.This question was investigated in a recent trial, in which 40patients were randomized to receive either propofol ordesflurane, both titrated to similar anesthetic depth as ob-tained by bispectral index (BIS), resulting also in similarhemodynamics [10]. While SrcO2 significantly decreasedin both groups in the first minutes after patients were lo-cated from the supine to the sitting position, values re-mained significantly higher in the desflurane group ascompared to the propofol group, despite lower bloodpressures. Furthermore, cerebral desaturations, defined asSrcO2 below 75 % of individual baseline values, occurredin two patients of the propofol group but in none of thedesflurane group. Unfortunately, measurements werestopped 9 min after positioning of the patients, preventingconclusions on the intraoperative course of SrcO2 as wellas on-going differences between anesthetic agents. Theauthors conclude that desflurane preserved cerebral oxy-genation better than propofol at equipotent anestheticconcentrations [10]. These observations are surprising atfirst sight, since it is long known that volatile anestheticsimpair autoregulation of cerebral blood flow more thanpropofol [11]. The authors speculate that desflurane (unlikepropofol) induced cerebral vasodilation and thus increasedcerebral blood flow (CBF), which in turn compensates thereduction in CBF following installation of the sitting po-sition. Otherwise, we may also speculate that the negativeimpact of propofol on venous return and thus cardiacoutput is huge in the present posture due to the venodilatoreffect of the drug.Another example of the clinical applicability of NIRStechnology to measure SrcO2 is presented in a case seriesof 20 patients undergoing major abdominal or urologicalsurgery under general anaesthesia [12]. The authors usedcontrolled hypotension induced by nitroglycerin (NTG) inorder to minimize blood loss and optimise surgical condi-tions. Vasodilation with NTG reduced MAP by about 20 %(from 90 ± 14 to 72 ± 14 mmHg), whereas it increasedSrcO2 in all patients by an average between 15 and 21 %.Although the authors did not measure blood flow (e.g.cardiac output) and did not report what NIRS device theyused, these findings demonstrate that blood pressure andtissue perfusion are not always related in a linear, positivefashion (uncoupling phenomenon). The authors discuss asa potential confounder that the volatile anaesthetics usedmight have led to luxury perfusion of the monitored brainarea while diverting blood away from potentially ischemicregions. [12] Nevertheless, this case series shows thatNIRS monitoring can be used to ensure the adequacy oftissue oxygenation during controlled hypotension and ex-pands the scope of conventional hemodynamic monitoringin this respect. This way it may contribute to improvepatient’s safety in case of macro-microcirculatorydecoupling.3 Interpretation of SrcO2 valuesSince there is no consensus about what should be consid-ered ‘‘normal values’’ for cerebral hemoglobin oxygensaturation, the authors of the previous study [8] come upwith a very interesting calculation: Assuming that a jugularbulb saturation (SjbO2, the gold standard for assessingcerebral hypoxemia) below 50 % indicates cerebral is-chemia, then with a ratio between arterial and venous bloodvolumes of 25:75 contributing to the SrcO2 signal dis-played on the monitor, as most NIRS devices adopt, we cancalculate which readings actually indicate cerebral is-chemia and which readings may assure us that this is notthe case [8]. In detail, if the SaO2 is 95 % and SjbO2 50 %,the resulting SrcO2 should be 61 %, which can be con-sidered as ‘‘normal’’. Thus with a standard deviation of5 % a SrcO2 measurement should be below 52 % (61-1.96 9 5 %) to be more than 95 % certain that the tissue isactually ischemic and above 71 % (61 ? 1.96 9 5 %) tobe certain that it is not, implying a large ‘‘grey zone’’ ofSrcO2 values where its diagnostic ability is inconclusive[13]. On the other hand, changing of the body position (e.g.head-up or head-down tilting) may change the ratio be-tween arterial and venous blood volumes of 25:75, so thatfor instance decreases in the SrcO2 readings are simply theresults of an increased proportion of venous blood con-tributing to the signal, rather than a true change in cerebraltissue oxygenation. In this respect, the higher SrcO2 valuesafter raising patients to the sitting position during desflu-rane anesthesia in the abovementioned study [10] could beinterpreted as evidence for cerebral arterial vasodilationunder desflurane and maintained cerebrovascular tone un-der propofol anesthesia.In conclusion, until a standardization of NIRS deviceshas been effectuated, the clinical context may influence thechoice of the adequate NIRS device for a specific purpose.Open Access This article is distributed under the terms of theCreative Commons Attribution License which permits any use, dis-tribution, and reproduction in any medium, provided the originalauthor(s) and the source are credited.References1. Scheeren TW, Schober P, Schwarte LA. Monitoring tissue oxy-genation by near infrared spectroscopy (NIRS): background andJ Clin Monit Comput (2015) 29:217–220 219123current applications. J Clin Monit Comput. 2012;26(4):279–87.doi:10.1007/s10877-012-9348-y.2. Kenosi M, Naulaers G, Ryan C, Dempsey E. Current researchsuggests that the future looks brighter for cerebral oxygenationmonitoring in preterm infants. Acta Paediatr. 2015;104(3):225–31. doi:10.1111/apa.12906.3. van Beest PA, Vos JJ, Poterman M, Kalmar AF, Scheeren TW.Tissue oxygenation as a target for goal-directed therapy in high-risk surgery: a pilot study. BMC Anesthesiol. 2014;14:122.doi:10.1186/1471-2253-14-122.4. van Beest PA, Scheeren TW. Tissue oxygen saturation as a goal,but when and where should we measure it? J Clin Monit Comput.2013;27(3):211–3. doi:10.1007/s10877-013-9438-5.5. Smith RS, Murkin JM. A novel assessment of peripheral tissuemicrocirculatory vasoreactivity using vascular occlusion testingduring cardiopulmonary bypass. J Cardiothorac Vasc Anesth.2014;28(5):1217–20. doi:10.1053/j.jvca.2014.03.016.6. Nygren A, Rennerfelt K, Zhang Q. Detection of changes inmuscle oxygen saturation in the human leg: a comparison of twonear-infrared spectroscopy devices. J Clin Monit Comput.2014;28(1):57–62. doi:10.1007/s10877-013-9494-x.7. Spruit RJ, Schwarte LA, Hakenberg OW, Scheeren TW. Asso-ciation of intraoperative tissue oxygenation with suspected riskfactors for tissue hypoxia. J Clin Monit Comput. 2013;27(5):541–50. doi:10.1007/s10877-013-9460-7.8. Hyttel-Sorensen S, Hessel TW, Greisen G. Peripheral tissueoximetry: comparing three commercial near-infrared spectroscopyoximeters on the forearm. J Clin Monit Comput. 2014;28(2):149–55. doi:10.1007/s10877-013-9507-9.9. Davie SN, Grocott HP. Impact of extracranial contamination onregional cerebral oxygen saturation: a comparison of three cere-bral oximetry technologies. Anesthesiology. 2012;116(4):834–40. doi:10.1097/ALN.0b013e31824c00d7.10. Kim JY, Lee JS, Lee KC, Kim HS, Kim SH, Kwak HJ. The effectof desflurane versus propofol on regional cerebral oxygenation inthe sitting position for shoulder arthroscopy. J Clin MonitComput. 2014;28(4):371–6. doi:10.1007/s10877-013-9543-5.11. Strebel S, Lam AM, Matta B, Mayberg TS, Aaslid R, NewellDW. Dynamic and static cerebral autoregulation during isoflu-rane, desflurane, and propofol anesthesia. Anesthesiology.1995;83(1):66–76.12. Van Noord BA, Stalker CL, Roffey P, Thangathurai D. The useof regional cerebral oximetry monitoring during controlled hy-potension: a case series. J Clin Monit Comput. 2014;28(3):319–23. doi:10.1007/s10877-013-9523-9.13. Ray P, Le Manach Y, Riou B, Houle TT. Statistical evaluation ofa biomarker. Anesthesiology. 2010;112(4):1023–40. doi:10.1097/ALN.0b013e3181d47604.220 J Clin Monit Comput (2015) 29:217–220123

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