We assessed accuracy of monitoring transcutaneous oxygen tension (PtcO2) in patients with chronic renal failure (CRF). Sixteen stable individuals undergoing chronic maintenance hemodialysis were studied. Correlations between simultaneously determined PtcO2 and arterial oxygen tension (PaO2) were made both before and during dialysis. Comparisons were made with a group of 22 consecutive patients in whom respiration was mechanically assisted, who were hemodynamically stable (urine output greater than 30 mL/hour, pulse less than 130 beats/min, and mean arterial blood pressure greater than 80 mm Hg in the absence of pressor agents), and who had normal renal function.
Among CRF patients, the correlation between PtcO2 and PaO2 was poor (R = .5232, p ⩽ .05), regardless of whether determined immediately before (R = .5454, p  ⩽ .05) or during hemodialysis (R = .4353, p =  ⩽  .05). In contrast, the PtcO2 correlated well with PaO2 among stable, mechanically ventilated patients (R = .9822, p  ⩽ .01). PtcO2 monitoring in patients with CRF requiring maintenance hemodialysis is of limited value whether performed before or during dialysis

Armstrong, John R.

Conway, William A.

Dumler, Francis

Kreps, Thomas W.

Popovich, John, Jr.

Henry Ford Health System Scholarly Commons

Henry Ford Hospital Medical Journal Volume 33 Number 1 Article 14 3-1985 The Invalidity of Monitoring Transcutaneous Oxygen Tension in Patients Who Have Chronic Renal Failure John R. Armstrong Thomas W. Kreps William A. Conway Francis Dumler John Popovich Jr. Follow this and additional works at: https://scholarlycommons.henryford.com/hfhmedjournal  Part of the Life Sciences Commons, Medical Specialties Commons, and the Public Health Commons Recommended Citation Armstrong, John R.; Kreps, Thomas W.; Conway, William A.; Dumler, Francis; and Popovich, John Jr. (1985) "The Invalidity of Monitoring Transcutaneous Oxygen Tension in Patients Who Have Chronic Renal Failure," Henry Ford Hospital Medical Journal : Vol. 33 : No. 1 , 57-60. Available at: https://scholarlycommons.henryford.com/hfhmedjournal/vol33/iss1/14 This Article is brought to you for free and open access by Henry Ford Health System Scholarly Commons. It has been accepted for inclusion in Henry Ford Hospital Medical Journal by an authorized editor of Henry Ford Health System Scholarly Commons. Henry Ford Hosp Med J 5ol 33. NO 1,1985 bas The Invalidity of Monitoring Transcutaneous Oxygen Tension in Patients Who Have Chronic Renal Failure John R. Armstrong, MD,* Thomas W. Kreps, BS+, William A. Conway, MD* Francis Dumler, MD* and John Popovich, Jr, MD* We assessed accuracy of monitoring transcutaneous oxygen tension (Ptc02) in patients with chronic renal failure (CRF). Sixteen stable individuals undergoing chronic maintenance hemodialysis were studied. Cor-relations between simultaneously determined PtcOz and arterial oxygen tension (PaOz) were made both before and during dialysis. Comparisons were made with a group of 22 consecutive patients in whom respi-ration was mechanically assisted, who were hemo-dynamically stable (urine output greater than 30 mU hour, pulse less than 130 beats/min, and mean arterial blood pressure greater than 80 mm Hg in the absence of pressor agents), and who had normal renal function. The reliability of transcutaneous oxygen monitors using heated plat inum electrodes to predict arterial oxygen tension (Pa02) has been demonstrated in neo-natal intensive care patients, selected adult intensive care patients, and dur ing exercise cardiopulmonary stress testing (1-3). The correlat ion between trans-cutaneous oxygen tension (PtcOi) and Pa02 in hemo-dynamically unstable patients, however, has been poor, probably as a result of redistribution of blood f low away from the cutaneous vascular bed (4). The accuracy of transcutaneous oxygen monitor ing in patients who have chronic renal failure (CRF) has not previously been studied. In view of the recognized phenomenon of dialysis-induced hypoxemia (5-6), its hemodynamic consequences (7-8), and the relative fre-quency with which patients who have CRF require in-tensive care, a simple inexpensive and noninvasive method of moni tor ing oxygenation could have sig-nificant clinical advantages. The present study evaluates the accuracy of Ptc02 monitor ing in patients who have CRF and who have been on maintenance ou tpu t hemodialysis. Methods Sixteen stable patients who had undergone chronic Inaintenance hemodialysis for a mean of 29 months (range of four to 32 months) were studied. Comparisons lyere made with a control group of 22 consecutive, Hemodynamically stable patients in whom respiration Was mechanically assisted and who had normal renal Among CRF patients, the correlation between Ptc02 and Pa02 was poor (R = .5232, p ^ .05), regardless of whether determined immediately before (R = .5454, p'^ .05) or during hemodialysis (R = .4353, p =e .05). In contrast, the Ptc02 correlated well with Pa02 among stable, mechanically ventilated patients (R = .9822, p « .01). Ptc02 monitoring in patients with CRF requiring main-tenance hemodialysis is of limited value whether per-formed before or during dialysis. funct ion. Hemodynamic stability was defined by the presence of all of the fo l lowing criteria: mean blood pressure greater than 80 mm Hg in the absence of pressor agents, urine output greater than 30 mL/hour, and pulse rate less than 130 beats/min. Ptc02 and Pa02 were simultaneously determined in both groups, and among chronic hemodialysis patients, measurements w e r e m a d e i m m e d i a t e l y p r i o r t o a n d d u r i n g hemodialysis. Ptc02 was measured using a Radiometer TcM 1 T<- oxy-gen monitor (Copenhagen, Denmark). The principle of operation is a Clark electrode consisting of a platinum cathode surrounded by a silver anode containing a heating element and NTC-resistor for temperature con-trol . A two-point calibration using atmospheric air ad-justed for barometric pressure and a zero PO2 sodium sulfite solution was established before placing the elec-trode on the right anterior chest below the clavicle. The electrode was maintained at45°Cand recalibrated every two hours and between each patient. A minimum of 20 min equil ibration t ime was allowed for placement be-fore readings were taken. Submitted for publication: April 17, 1985 Accepted for publication: May 14, 1985 •Department of Medicine, Division of Pulmonary and Critical Care Medicine, Henry Ford Hospital "•"Department of Respiratory Therapy, Henry Ford Hospital ^Department of Medicine, Division of Nephrology and Hypertension, Henry Ford Hospital Address reprint requests to Dr Popovich, Department of Medicine, Henry Ford Hospital, 2799 W Crand Blvd, Detroit, Ml 48202. 57 A r m s t r o n g , Kreps, C o n w a y , et al Simultaneously collected arterial blood samples were obtained via direct arterial puncture or an indwell ing arterial catheter, when present. Specimens were iced and immediately processed through an 1L513 Blood Cas Analyzer ( Instrumentat ion Laboratories, Lexington, Massachusetts). All arterial blood gasses were tempera-ture corrected according to standard formulas (9). PtcOj , Pa02, ur ine ou tpu t , pulse, b lood pressure, hematocrit value and, when appropriate, length of time on the current hemodialysis run were recorded at the t ime of measurement. Results Table I displays patient data for each group. Except for pulse rate, wh i ch was h igher among the cont ro l patients, there were no significant differences between groups for the variables noted. The correlation coefficients and regression data for Ptc02 and Pa02 for the same groups are shown in Table I I . The correlation for Ptc02 and Pa02 among patients who have renal failure is significantly lower than con-trols, whether monitor ing occurred during the hemo-dialysis run or between dialyses. The corresponding scatter plots and regression lines are shown in Figures 1, 2, and 3. The mean difference between Pa02 and PtcOz for control subjects and patients who have CRF was 10.3 ± 1.8 torr and 11.6 ± 3.6 forr, respectively (p< .OS Review of the CRF data showed that the Ptc02 tracked ini the same direction as the Pa02 in only seven of IS patients in whom serial determinations were made To evaluate the possible effects of anemia on the cop relation between Ptc02 and Pa02, we matched contrd subjects and CRF patients by hematocrit levels. Anemii| control subjects continued to show a significantly higher correlation coefficient than did patients who haj CRF at the same hematocrit level (Table 111). Discussion The amount of oxygen dif fusing through the skin m reach the transcutaneous electrode varies in a numbei of condit ions. Skin thickness, cutaneous oxygen con-sumption, and local perfusion levels all influence this phenomenon (1,2,10). A fall in Ptc02 may signify a hemodynamic alteration rather than a true change i | arterial oxygenation in some circumstances. Oxygei transport gradients across the skin have clearly beei shown to change with local temperature f luctuat ion alterations in cardiac output , peripheral vascular resi j tance, and total oxygen transport (4). Al though changel in Ptc02 do not always reflect changes in Pa02, they m ^ serve as an early warning sign of subtle alterations i n i patient's condit ion. Table I Patient Data Sex (M/F) Age (years) Pulse (beat/min) Mean b lood Pressure (mm Hg) 'Group means and standard error ••"p < .05 when compared to controls Controls 13/9 58.8 ± 2.8 110.0 ± 1.5 93.8 ± 1.2 Chronic Renal Failure 6/10 58.9 ± 2.2 Interdialysis Period 89 ± 3.1 91 ± 4.6 Dur ing Hemodialysis 8b 89 2.0 4.4 Table l i Comparison of Correlations of PtcOj wi th PaOj Number of Observations PaOs (mm Hg mean ± SE)* Regression Coef f ic ient ' Correlat ion Coefficient'!' Controls 41 109 ± 9.4 .9348 .9822 CRF total 38 79 ± 2.0 .8547 .5232 CRF interdialysis per iod 13 84 ± 4.1 .5491 .5450 CRF dur ing hemodialysis 25 76 ± 1.8 .9141 .4353 •p <.05 for Pa02 and regression coefficient between controls and all CRF groups "•"Significant difference between the correlation coefficient of control and CRF groups (p < .01) 58 Ptc02 Intercept im Hg mean ± S - 3.22 ± 3.5 - 3.97 ± 18.0 28.40 ± 21.8 -11 .90 ± 30.0 Monitoring Transcutaneous Oxygen Tension / (p< .05 .tracked ill ;ven of 15 e made. ] )n the COr; ied contro ;ls. Anemic gnificantl' its who hai the skin toi T a number xygen con-luence this ly signify ! ; change in 2s. Oxygen learly been fluctuation; icular resiS' Igh change! )2, they ma} jrations ins /SIS 5 rcept an ± SE) : 3.5 18.0 t 21.8 30.0 Table l l i Correlation Coefficient of Ptc02 with Pa02 Among Patients Matched for Hematocrit Controls CRF Number of Observations 19 16 PaOj (mm Hg mean ± SE)* 121 ± 17.7 79 ± 3.3 Correlat ion Coeff ic ient* .9898 .7009 Mean Hematocrit ' ' ' 29.0 ± .55 27.6 ± .82 •Significant difference between controls and CRF patients values, for Pa02 and correlation coefficients (p<.01) tNo significant difference between control and CRF patients at matched hematocrit Line of Identity Regression Line 40 50 60 70 80 90 100 110 120 Pa02 (mmHg) F i g i Plot of PtcOi vs PaOj in 13 patients who had chronic renal failure (CRF) prior to hemodialysis run. R = .5454, p « .05. The Ptc02 has been shown to correlate very well wi th the Pa02 over a wide range of arterial oxygen levels under conditions of adequate cardiac output (4). This was confirmed in the present study among the hemo-dynamically stable patients undergoing venti lat ion. The poor correlat ion between Ptc02 and Pa02 among patients who had CRF, both dur ing hemodialysis and in the interdialysis per iod, was unexpected. Hypoxia, as well as several hemodynamic changes, has occurred in response to hemodialysis. Decrease in pulmonary ar-terial pressure, cardiac index, and stroke index, wi thout 3n increase in heart rate or even a paradoxical bradycar-dia, have been documented (7,8). These may occur Without significant change in mean arterial pressure and perhaps could alter oxygen transport sufficiently to cause a variable and disproport ionate lowering of the tcOj relative to Pa02. However, the reason for the poor correlation of Ptc02 wi th PaOj dur ing the inter-•alysis interval remains unclear. Tissue edema may ave been a factor although peridialysis weights in "ese selected patients were not much above their 100 -P t c O j (mmHg) gO Line of Identity Regression Line 40 60 80 100 Pa02 (mmHg) Fig 2 Plot of Ptc02 vs Pa02 in 25 patients who had CRF and were undergoing dialysis. R = .04353, p « .05. 280 PtcOz (mmHg) 200 120 80-Lineof Identity Regression Line PaOs (mmHg) Plot of Ptc02 vs PaO Fig 3 in 41 control patients. R .9822, p « .01. 59 Armstrong, Kreps, Conway, et al dry-target weight . Other speculative considerations might include changes in P50 (11) or the presence of a microvascular disease affecting cutaneous perfusion. Even so, the Ptc02 did not consistently track in the same direction as the PaOz in almost 50% of determinations. In an effort to determine if a lower arterial O2 content may have affected the transport gradient in our CRF patients, we used control subjects whose low hemat-ocrit values were matched wi th those of the patients for comparison. Patients who were anemic and who had normal renal function cont inued to have a significantly higher correlation of Ptc02 with Pa02 than patients who had CRF at the same hematocrit level (p< .01). We conclude that moni tor ing transcutaneous oxygenj concentration in patients who have CRF and who resl quire maintenance hemodialysis is not helpful . Thisis true whether monitor ing occurs dur ing hemodialysis 01 in the interdialysis interval. PtcOj readings in these patients are not a reliable indicator of either changes in arterial oxygenation or other parameters that can affea the cutaneous O2 gradient. Further studies are needed to explore the potent ia l causative factors for tha phenomenon. References 1 Huch R Huch A, Albani M, et al. Transcutaneous PO, monitormg in routine management of infants and children with cardi-orespiratory problems. Pediatrics 1976;57:681. 2 Rooth G, Hedstrand U, Tyden H, et al. The validity of the trans-cutaneous oxygen tension methods in adults. Cnt Care Med 1976,4:162. 3 Schonfeld T, Sargent CW, Bautista D, et al. Transcutaneous oxy-gen monitoring during exercise stress testing. Am Rev Respir Dis 1980;121:458-62. 4 Tremper KK, Shoemaker WC. Transcutaneous oxygen monitor-ing of critically ill adults with and without low flow shock. Cnt Care Med 1981;9:706-9. Patterson RW, Nissenson AR, Miller J, Smith RT, Narins RG, Sullivan SF. Hypoxemia and pulmonary gas exchange during hemodialysis. ) Appl Physiol 1981;50:259-64. Burns CB, Scheinhorn DJ. Hypoxemia during hemodialysis. Arch Intern Med 1982;142:1350-3. 5-6. 10. 11 Azancot 1, Degoulet P, Juillet Y, et al. Hemodynamic evaluationol hypotension during chronic hemodialysis. Clin Nephr« 1977;8:312. Endou K, Kamuimo ), Kakubari Y, Kikawada R. Hemodynamic changes during hemodialysis. Cardiology 1978;63:175. Kelman GR, Nunn )F. Nomograms for correction of blood POi PCO2, pH, and base excess for time and temperature. J Appl Physiol 1966;21:1484. Goeckenjaw G, Strasser K. Relation of transcutaneous to arteriJ P02 in hypoxemia, normoxemia, hyperoxemia: Investigations 11 adults with normal circulation and in patients with circulatoB insufficiency. Biotelemetry 1977;4;77. HIastala MP, Woodson RD. Saturation dependency of the Bohi effect: Interactions among H* C02, and DPG. J Appl Physid 1975;38:1126. 60 

The Invalidity of Monitoring Transcutaneous Oxygen Tension in Patients Who Have Chronic Renal Failure

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