Cerebral autoregulation and cerebral blood flow response to mean arterial pressure challenge following induction of general anaesthesia for neuroradiology procedure

IntroductionIntraoperative hypotension is common following general anaesthesia induction with propofol, but its impact on cerebral autoregulation (CA) remains unclear. We investigate the incidence and risk factors of impaired CApost-propofol induction and its recovery after a mean arterial pressure (mAP) challenge.MethodsWe included 40 non-emergency neuroradiology surgery patients [58 (47, 58)years old., 57% women]. We recorded mAP, mean blood flow velocity in the mean cerebral artery (MCAvmean), and regional cerebral oxygen saturation (rSO2). We computed the mean flow index (Mxa) pre and post mAP challenge. Mxa > 0.3 defined poor CA.ResultsAfter anaesthesia induction, 21 (53%) had impaired CBF autoregulation (CA−, Mxa > 0.3). The average mAP was 66 ± 9 mmHg, average MCAv was 39 ± 12 cm.s−1, and rSO2 was 63 ± 7%. We found no significant difference in age, norepinephrine infusion rate, and cardiovascular risks factors were similar between CA− and CA+ (Mxa ≤ 0.3) patients. Among the 22 patients (CA−: n = 14; CA+: n = 8) undergoing mAP challenge, there was a significant Mxa improvement and MCAv increase among CA− patients, (CA−: 0.63 ± 0.18 vs. 0.28 ± 0.20, p < 0.001), and [absolute variation: 1 (0.7–1.5) vs. 7 (3–9) cm.sec−1], respectively.ConclusionAfter induction of general anaesthesia for neuroradiology procedure, 53% of the patients had an impaired CA, regardless of age or medical history. Importantly, a mAP challenge effectively restored CA and improved CBF.Clinical Trial Registrationidentifier, NCT0428886

Norepinephrine reduces arterial compliance less than phenylephrine when treating general anesthesia-induced arterial hypotension

International audienceIntroduction: During general anesthesia, arterial hypotension is frequent and may be an important contributor to peri-operative morbidity. We assessed the effect of a 5µg bolus of Norepinephrine (NA) when compared with 50 µg bolus of Phenylephrine (PE) administered to treat hypotension during maintenance anesthesia, on MAP, derived cardiac output and arterial stiffness parameters. Methods: Patients scheduled for a neurosurgical procedure under general anesthesia were prospectively included. Monitoring included invasive blood pressure, esophageal Doppler and arterial tonometer used to estimate central aortic pressure with arterial stiffness parameters, such as augmentation index (Aix). After initial resuscitation, hypotensive episodes were corrected by a bolus administration of NA or PE in a peripheral venous line. Results: There were 269 bolus administrations of vasopressors (149 NA, 120 PE) in 47 patients with no adverse effects detected. A decrease in stroke volume (SV) was observed with PE compared with NA (-18±9% vs -14±7%, p<0.001). This decrease was associated with an increase in Aix, which was greater for PE than for NA (+10±8% vs +6±6%, p<0.0001), and a decrease in total arterial compliance greater for PE compared to NA (Ctot=SV/Central Pulse Pressure) (-35±9% vs. -29±10%, p<0.001). Discussion: This study suggests that 5 µg of NA administered as a bolus in a peripheral venous line could treat general-anesthesia-induced arterial hypotension with a smaller decrease in SV and arterial compliance when compared to PE

Cerebral autoregulation and cerebral blood flow response to mean arterial pressure challenge following induction of general anaesthesia for neuroradiology procedure

International audienceIntroduction Intraoperative hypotension is common following general anaesthesia induction with propofol, but its impact on cerebral autoregulation (CA) remains unclear. We investigate the incidence and risk factors of impaired CApost-propofol induction and its recovery after a mean arterial pressure (mAP) challenge. Methods We included 40 non-emergency neuroradiology surgery patients [58 (47, 58)years old., 57% women]. We recorded mAP, mean blood flow velocity in the mean cerebral artery (MCAv$_{ mean}$ ), and regional cerebral oxygen saturation (rSO2). We computed the mean flow index (Mxa) pre and post mAP challenge. Mxa > 0.3 defined poor CA. Results After anaesthesia induction, 21 (53%) had impaired CBF autoregulation (CA−, Mxa < 0.3). The average mAP was 66 ± 9 mmHg, average MCAv was 39 ± 12 cm.s$^{−1}$ , and rSO 2 was 63 ± 7%. We found no significant difference in age, norepinephrine infusion rate, and cardiovascular risks factors were similar between CA− and CA+ (Mxa ≤ 0.3) patients. Among the 22 patients (CA−: n = 14; CA+: n = 8) undergoing mAP challenge, there was a significant Mxa improvement and MCAv increase among CA− patients, (CA−: 0.63 ± 0.18 vs. 0.28 ± 0.20, p < 0.001), and [absolute variation: 1 (0.7–1.5) vs. 7 (3–9) cm.sec$^{−1}$ ], respectively. Conclusion After induction of general anaesthesia for neuroradiology procedure, 53% of the patients had an impaired CA, regardless of age or medical history. Importantly, a mAP challenge effectively restored CA and improved CBF. Clinical Trial Registration identifier, NCT0428886

Beat-by-beat assessment of cardiac afterload using descending aortic velocity–pressure loop during general anesthesia: a pilot study

International audienceIntroduction:Continuous cardiac afterload evaluation could represent a useful tool during general anesthesia (GA) to titrate vasopressor effect. Using beat to beat descending aortic pressure(P)/flow velocity(U) loop obtained from esophageal Doppler and femoral pressure signals might allow to track afterload changes.Methods:We defined 3 angles characterizing the PU loop (alpha, beta and Global After-Load Angle(GALA)). Augmentation index (AIx) and total arterial compliance (Ctot) were measured via radial tonometry. Peripheral Vascular Resistances (PVR) were also calculated.Twenty patients were recruited and classified into low and high cardiovascular (CV) risk group. Vasopressors were administered, when baseline mean arterial pressure (MAP) fell by 20%. Results:We studied 118 pairs of pre/post bolus measurements.At baseline, patients in the lower CV risk group had higher cardiac output (6.1±1.7 vs 4.2±0.6 L/min; p= 0.005), higher Ctot (2.7±1.0 vs 2.0±0.4ml/mmHg, p = 0.033), lower Aix and PVR (13±10 vs 32±11% and 1011±318 vs 1390±327 dyn.s.cm-5; p<0.001 and p=0.016, respectively) and lower GALA (41±15 vs ± 6°; p <0.001). GALA was the only PU Loop parameterassociated with Ctot, Aix and PVR.After vasopressors, MAP increase was associated with a decrease in Ctot, an increase in Aix and PVR and an increase in alpha, beta and GALA (p<0.001 for all). Changes in GALA and Ctot after vasopressors were strongly associated (p=0.004).Conclusions:PU Loop assessment from routine invasive hemodynamic optimization management during GA and especially GALA parameter could monitor cardiac afterload continuously in anesthetized patients, and may help clinicians to titratevasopressor therapy

Propofol Requirement and EEG Alpha Band Power During General Anesthesia Provide Complementary Views on Preoperative Cognitive Decline

International audienceBackground: Although cognitive decline (CD) is associated with increased post-operative morbidity and mortality, routinely screening patients remains difficult. The main objective of this prospective study is to use the EEG response to a Propofol-based general anesthesia (GA) to reveal CD. Methods: 42 patients with collected EEG and Propofol target concentration infusion (TCI) during GA had a preoperative cognitive assessment using MoCA. We evaluated the performance of three variables to detect CD (MoCA &lt; 25 points): age, Propofol requirement to induce unconsciousness (TCI at SEF 95 : 8–13 Hz) and the frontal alpha band power (AP at SEF 95 : 8–13 Hz). Results: The 17 patients (40%) with CD were significantly older ( p &lt; 0.001), had lower TCI ( p &lt; 0.001), and AP ( p &lt; 0.001). We found using logistic models that TCI and AP were the best set of variables associated with CD (AUC: 0.89) and performed better than age ( p &lt; 0.05). Propofol TCI had a greater impact on CD probability compared to AP, although both were complementary in detecting CD. Conclusion: TCI and AP contribute additively to reveal patient with preoperative cognitive decline. Further research on post-operative cognitive trajectory are necessary to confirm the interest of intra operative variables in addition or as a substitute to cognitive evaluation

Impact of impaired cerebral blood flow autoregulation on electroencephalogram signals in adults undergoing propofol anaesthesia: a pilot study

International audienceBackground: Cerebral autoregulation actively maintains cerebral blood flow over a range of MAPs. During general anaesthesia, this mechanism may not compensate for reductions in MAP leading to brain hypoperfusion. Cerebral autoregulation can be assessed using the mean flow index derived from Doppler measurements of average blood velocity in the middle cerebral artery, but this is impractical for routine monitoring within the operating room. Here, we investigate the possibility of using the EEG as a proxy measure for a loss of cerebral autoregulation, determined by the mean flow index. Methods: Thirty-six patients (57.5 [44.25; 66.5] yr; 38.9% women, non-emergency neuroradiology surgery) anaesthetised using propofol were prospectively studied. Continuous recordings of MAP, average blood velocity in the middle cerebral artery, EEG, and regional cerebral oxygen saturation were made. Poor cerebral autoregulation was defined as a mean flow index greater than 0.3. Results: Eighteen patients had preserved cerebral autoregulation, and 18 had altered cerebral autoregulation. The two groups had similar ages, MAPs, and average blood velocities in the middle cerebral artery. Patients with altered cerebral autoregulation exhibited a significantly slower alpha peak frequency (9

Velocity–pressure loops for continuous assessment of ventricular afterload: influence of pressure measurement site

International audienceVPloop, the graphical representation of pressure versus velocity, and its characteristic angles, GALA and β, can be used to monitor cardiac afterload during anesthesia. Ideally VPloop should be measured from pressure and velocity obtained at the same arterial location but standard of care usually provide either radial or femoral pressure waveforms. The purpose of this study was to look at the influence of arterial sites and the use of a transfer function (TF) on VPloop and its related angles. Invasive pressure signals were recorded in 25 patients undergoing neuroradiology intervention under general anesthesia with transesophageal flow velocity monitoring. Pressures were recorded in the descending thoracic aorta, abdominal aorta, femoral and radial arteries. We compared GALA and β from VPloops generated from each location and in high and low risk patients. GALA was similar in the central locations (55°[49–63], 52°[47–61] and 54°[45–62] from descending thoracic to femoral artery, median[interquartile], p = 0.10), while there was a difference in β angle (16°[4–27] to 8°[3–15], p < 0.0001). GALA and β obtained from radial waveforms were different (39°[31–47] compared to 46°[36–54] and 6°[2–14] compared to 16°[4–27] for GALA and β angles respectively, p < 0.001) which was corrected by the use of a TF (45°[32–55] and 17°[5–28], p = ns). GALA and β are underestimated when measured with a radial catheter. Using pressure waveforms from femoral locations alters VPloops, GALA and β in a smaller extend. The use of a TF on radial pressure allows to correctly plot VPloops and their characteristic angles for routine clinical use