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Optimal blood pressure during cardiopulmonary bypass defined by cerebral autoregulation monitoring.

ABSTRACT: OBJECTIVES:We sought to define the lower and upper limits of cerebral blood flow autoregulation and the optimal blood pressure during cardiopulmonary bypass. We further sought to identify variables predictive of these autoregulation end points. METHODS:Cerebral autoregulation was monitored continuously with transcranial Doppler in 614 patients during cardiopulmonary bypass enrolled in 3 investigations. A moving Pearson's correlation coefficient was calculated between cerebral blood flow velocity and mean arterial pressure to generate the variable mean velocity index. Optimal mean arterial pressure was defined as the mean arterial pressure with the lowest mean velocity index indicating the best autoregulation. The lower and upper limits of cerebral blood flow autoregulation were defined as the mean arterial pressure at which mean velocity index was increasingly pressure passive (ie, mean velocity index ?0.4) with declining or increasing blood pressure, respectively. RESULTS:The mean (± standard deviation) lower and upper limits of cerebral blood flow autoregulation, and optimal mean arterial pressure were 65 ± 12 mm Hg, 84 ± 11 mm Hg, and 78 ± 11 mm Hg, respectively, after adjusting for study enrollment. In 17% of patients, though, the lower limit of cerebral autoregulation was above this optimal mean arterial pressure, whereas in 29% of patients the upper limit of autoregulation was below the population optimal mean arterial pressure. Variables associated with optimal mean arterial pressure based on multivariate regression analysis were nonwhite race (increased 2.7 mm Hg; P = .034), diuretics use (decreased 1.9 mm Hg; P = .049), prior carotid endarterectomy (decreased 5.5 mm Hg; P = .019), and duration of cardiopulmonary bypass (decreased 1.28 per 60 minutes of cardiopulmonary bypass). The product of the duration and magnitude that mean arterial pressure during cardiopulmonary bypass was below the lower limit of cerebral autoregulation was associated with the risk for stroke (P = .02). CONCLUSIONS:Real-time monitoring of autoregulation may improve individualizing mean arterial pressure during cardiopulmonary bypass and improving patient outcomes.

SUBMITTER: Hori D

PROVIDER: S-EPMC5685671 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature

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Optimal blood pressure during cardiopulmonary bypass defined by cerebral autoregulation monitoring.

Hori Daijiro D Nomura Yohei Y Ono Masahiro M Joshi Brijen B Mandal Kaushik K Cameron Duke D Kocherginsky Masha M Hogue Charles W CW

The Journal of thoracic and cardiovascular surgery 20170724 5

<h4>Objectives</h4>We sought to define the lower and upper limits of cerebral blood flow autoregulation and the optimal blood pressure during cardiopulmonary bypass. We further sought to identify variables predictive of these autoregulation end points.<h4>Methods</h4>Cerebral autoregulation was monitored continuously with transcranial Doppler in 614 patients during cardiopulmonary bypass enrolled in 3 investigations. A moving Pearson's correlation coefficient was calculated between cerebral bloo ...[more]

PMID: 29042040

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Project description:ImportanceDelirium occurs in up to 52% of patients after cardiac surgery and may result from changes in cerebral perfusion. Using intraoperative cerebral autoregulation monitoring to individualize and optimize cerebral perfusion may be a useful strategy to reduce the incidence of delirium after cardiac surgery.ObjectiveTo determine whether targeting mean arterial pressure during cardiopulmonary bypass (CPB) using cerebral autoregulation monitoring reduces the incidence of delirium compared with usual care.Design, setting, and participantsThis randomized clinical trial nested within a larger trial enrolled patients older than 55 years who underwent nonemergency cardiac surgery at a single US academic medical center between October 11, 2012, and May 10, 2016, and had a high risk for neurologic complications. Patients, physicians, and outcome assessors were masked to the assigned intervention. A total of 2764 patients were screened, and 199 were eligible for analysis in this study.InterventionIn the intervention group, the patient's lower limit of cerebral autoregulation was identified during surgery before CPB. On CPB, the patient's mean arterial pressure was targeted to be greater than that patient's lower limit of autoregulation. In the control group, mean arterial pressure targets were determined according to institutional practice.Main outcomes and measuresThe main outcome was any incidence of delirium on postoperative days 1 through 4, as adjudicated by a consensus expert panel.ResultsAmong the 199 participants in this study, mean (SD) age was 70.3 (7.5) years and 150 (75.4%) were male. One hundred sixty-two (81.4%) were white, 26 (13.1%) were black, and 11 (5.5%) were of other race. Of 103 patients randomized to usual care, 94 were analyzed, and of 102 patients randomized to the intervention 105 were analyzed. Excluding 5 patients with coma, delirium occurred in 48 of the 91 patients (53%) in the usual care group compared with 39 of the 103 patients (38%) in the intervention group (P = .04). The odds of delirium were reduced by 45% in patients randomized to the autoregulation group (odds ratio, 0.55; 95% CI, 0.31-0.97; P = .04).Conclusions and relevanceThe results of this study suggest that optimizing mean arterial pressure to be greater than the individual patient's lower limit of cerebral autoregulation during CPB may reduce the incidence of delirium after cardiac surgery, but further study is needed.Trial registrationClinicalTrials.gov identifier: NCT00981474.

Project description:BackgroundPatient rewarming after hypothermic cardiopulmonary bypass (CPB) has been linked to brain injury after cardiac surgery. In this study, we evaluated whether cooling and then rewarming of body temperature during CPB in adult patients is associated with alterations in cerebral blood flow (CBF)-blood pressure autoregulation.MethodsOne hundred twenty-seven adult patients undergoing CPB during cardiac surgery had transcranial Doppler monitoring of the right and left middle cerebral artery blood flow velocity. Eleven patients undergoing CPB who had arterial inflow maintained at >35 degrees C served as controls. The mean velocity index (Mx) was calculated as a moving, linear correlation coefficient between slow waves of middle cerebral artery blood flow velocity and mean arterial blood pressure. Intact CBF-blood pressure autoregulation is associated with an Mx that approaches 0. Impaired autoregulation results in an increasing Mx approaching 1.0. Comparisons of time-averaged Mx values were made between the following periods: before CPB (baseline), during the cooling and rewarming phases of CPB, and after CPB. The number of patients in each phase of CPB with an Mx >4.0, indicative of impaired CBF autoregulation, was determined.ResultsDuring cooling, Mx (left, 0.29 +/- 0.18; right, 0.28 +/- 0.18 [mean +/- SD]) was greater than that at baseline (left, 0.17 +/- 0.21; right, 0.17 +/- 0.20; P <or= 0.0001). Mx increased during the rewarming phase of CPB (left, 0.40 +/- 0.19; right, 0.39 +/- 0.19) compared with baseline (P <or= 0.001) and the cooling phase (P <or= 0.0001), indicating impaired CBF autoregulation. After CPB, Mx (left, 0.27 +/- 0.20; right, 0.28 +/- 0.21) was higher than at baseline (left, P = 0.0004; right, P = 0.0003), no different than during the cooling phase, but lower than during rewarming (left, P <or= 0.0001; right, P <or= 0.0005). Forty-three patients (34%) had an Mx >or=0.4 during the cooling phase of CPB and 68 (53%) had an average Mx >or=0.4 during rewarming. Nine of the 11 warm controls had an average Mx >or=0.4 during the entire CPB period. There were 7 strokes and 1 TIA after surgery. All strokes were in patients with Mx >or= 0.4 during rewarming (P = 0.015). The unadjusted odds ratio for any neurologic event (stroke or transient ischemic attack) for patients with Mx >or= 0.4 during rewarming was 6.57 (95% confidence interval, 0.79 to 55.0, P < 0.08).ConclusionsHypothermic CPB is associated with abnormal CBF-blood pressure autoregulation that is worsened with rewarming. We found a high rate of strokes in patients with evidence of impaired CBF autoregulation. Whether a pressure-passive CBF state during rewarming is associated with risk for ischemic brain injury requires further investigation.

Project description:BackgroundImpaired cerebral autoregulation and cerebral hypoperfusion may play a critical role in the high morbidity and mortality in patients with sepsis-associated encephalopathy (SAE). Bedside assessment of cerebral autoregulation may help individualize hemodynamic targets that optimize brain perfusion. We hypothesize that near-infrared spectroscopy (NIRS)-derived cerebral oximetry can identify blood pressure ranges that enhance autoregulation in patients with SAE and that disturbances in autoregulation are associated with severity of encephalopathy.MethodsAdult patients with acute encephalopathy directly attributable to sepsis were followed using NIRS-based multimodal monitoring for 12 consecutive hours. We used the correlation in time between regional cerebral oxygen saturation and mean arterial pressure (MAP) to determine the cerebral oximetry index (COx) as a measure of cerebral autoregulation. Autoregulation curves were constructed for each patient with averaged COx values sorted by MAP in 3 sequential 4-hour periods; the optimal pressure (MAPOPT), defined as the MAP associated with most robust autoregulation (lowest COx), was identified in each period. Severity of encephalopathy was measured with Glasgow coma scale (GCS).ResultsSix patients with extracranial sepsis met the stringent criteria specified, including no pharmacological sedation or neurologic premorbidity. Optimal MAP was identified in all patients and ranged from 55 to 115 mmHg. Additionally, MAPOPT varied within individual patients over time during monitoring. Disturbed autoregulation, based on COx, was associated with worse neurologic status (GCS < 13) both with and without controlling for age and severity of sepsis (adjusted odds ratio [OR]: 2.11; 95% confidence interval [CI]: 1.77-2.52; P < .001; OR: 2.97; 95% CI: 1.63-5.43; P < .001).ConclusionsIn this high-fidelity group of patients with SAE, continuous, NIRS-based monitoring can identify blood pressure ranges that improve autoregulation. This is important given the association between cerebral autoregulatory function and severity of encephalopathy. Individualizing blood pressure goals using bedside autoregulation monitoring may better preserve cerebral perfusion in SAE than current practice.

Project description:BackgroundImpaired cerebral blood flow (CBF) autoregulation during cardiopulmonary bypass (CPB) is associated with stroke and other adverse outcomes. Large and small arterial stenosis is prevalent in patients undergoing cardiac surgery. We hypothesize that large and/or small vessel cerebral arterial disease is associated with impaired cerebral autoregulation during CPB.MethodsA retrospective cohort analysis of data from 346 patients undergoing cardiac surgery with CPB enrolled in an ongoing prospectively randomized clinical trial of autoregulation monitoring were evaluated. The study protocol included preoperative transcranial Doppler (TCD) evaluation of major cerebral artery flow velocity by a trained vascular technician and brain magnetic resonance imaging (MRI) between postoperative days 3 and 5. Brain MRI images were evaluated for chronic white matter hyperintensities (WMHI) by a vascular neurologist blinded to autoregulation data. "Large vessel" cerebral vascular disease was defined by the presence of characteristic TCD changes associated with stenosis of the major cerebral arteries. "Small vessel" cerebral vascular disease was defined based on accepted scoring methods of WMHI. All patients had continuous TCD-based autoregulation monitoring during surgery.ResultsImpaired autoregulation occurred in 32.4% (112/346) of patients. Preoperative TCD demonstrated moderate-severe large vessel stenosis in 67 (25.2%) of 266 patients with complete data. In adjusted analysis, female sex (odds ratio [OR], 0.46; 95% confidence interval [CI], 0.25-0.86; P = .014) and higher average temperature during CPB (OR, 1.23; 95% CI, 1.02-1.475; P = .029), but not moderate-severe large cerebral arterial stenosis (P = .406), were associated with impaired autoregulation during CPB. Of the 119 patients with available brain MRI data, 42 (35.3%) demonstrated WMHI. The presence of small vessel cerebral vascular disease was associated with impaired CBF autoregulation (OR, 3.25; 95% CI, 1.21-8.71; P = .019) after adjustment for age, history of peripheral vascular disease, preoperative hemoglobin level, and preoperative treatment with calcium channel blocking drugs.ConclusionsThese data confirm that impaired CBF autoregulation is prevalent during CPB predisposing affected patients to brain hypoperfusion or hyperperfusion with low or high blood pressure, respectively. Small vessel, but not large vessel, cerebral vascular disease, male sex, and higher average body temperature during CPB appear to be associated with impaired autoregulation.

Project description:BackgroundClassically, cerebral autoregulation (CA) entails cerebral blood flow (CBF) remaining constant by cerebrovascular tone adapting to fluctuations in mean arterial pressure (MAP) between ∼60 and ∼150 mmHg. However, this is not an on-off mechanism; previous work has suggested that vasomotor tone is proportionally related to CA function. During propofol-based anaesthesia, there is cerebrovascular vasoconstriction, and static CA remains intact. Sevoflurane-based anaesthesia induces cerebral vasodilation and attenuates CA dose-dependently. It is unclear how this translates to dynamic CA across a range of blood pressures in the autoregulatory range.ObjectiveThe aim of this study was to quantify the effect of step-wise increases in MAP between 60 and 100 mmHg, using phenylephrine, on dynamic CA during propofol- and sevoflurane-based anaesthesia.DesignA nonrandomised interventional trial.SettingSingle centre enrolment started on 11 January 2019 and ended on 23 September 2019.PatientsWe studied American Society of Anesthesiologists (ASA) I/II patients undergoing noncardiothoracic, nonneurosurgical and nonlaparoscopic surgery under general anaesthesia.InterventionIn this study, cerebrovascular tone was manipulated in the autoregulatory range by increasing MAP step-wise using phenylephrine in patients receiving either propofol- or sevoflurane-based anaesthesia. MAP and mean middle cerebral artery blood velocity (MCA Vmean ) were measured in ASA I and II patients, anaesthetised with either propofol ( n = 26) or sevoflurane ( n = 28), during 10 mmHg step-wise increments of MAP between 60 and 100 mmHg. Static CA was determined by plotting 2-min averaged MCA Vmean versus MAP. Dynamic CA was determined using transfer function analysis and expressed as the phase lead (°) between MAP and MCA Vmean oscillations, created with positive pressure ventilation with a frequency of 6 min -1 .Main outcomesThe primary outcome of this study was the response of dynamic CA during step-wise increases in MAP during propofol- and sevoflurane-based anaesthesia.ResultsMAP levels achieved per step-wise increments were comparable between anaesthesia regiment (63 ± 3, 72 ± 2, 80 ± 2, 90 ± 2, 100 ± 3 mmHg, and 61 ± 4, 71 ± 2, 80 ± 2, 89 ± 2, 98 ± 4 mmHg for propofol and sevoflurane, respectively). MCA Vmean increased more during step-wise MAP increments for sevoflurane compared to propofol ( P ≤0.001). Dynamic CA improved during propofol (0.73° mmHg -1 , 95% CI 0.51 to 0.95; P ≤ 0.001)) and less pronounced during sevoflurane-based anaesthesia (0.21° mmHg -1 (95% CI 0.01 to 0.42, P = 0.04).ConclusionsDuring general anaesthesia, dynamic CA is dependent on MAP, also within the autoregulatory range. This phenomenon was more pronounced during propofol anaesthesia than during sevoflurane.Trial registrationNCT03816072 ( https://clinicaltrials.gov/ct2/show/NCT03816072 ).

Project description:Clinical monitoring of cerebral blood flow (CBF) autoregulation in patients undergoing liver transplantation may provide a means for optimizing blood pressure to reduce the risk of brain injury. The purpose of this pilot project is to test the feasibility of autoregulation monitoring with transcranial Doppler (TCD) and near-infrared spectroscopy (NIRS) in patients undergoing liver transplantation and to assess changes that may occur perioperatively.We performed a prospective observational study in 9 consecutive patients undergoing orthotopic liver transplantation. Patients were monitored with TCD and NIRS. A continuous Pearson's correlation coefficient was calculated between mean arterial pressure (MAP) and CBF velocity and between MAP and NIRS data, rendering the variables mean velocity index (Mx) and cerebral oximetry index (COx), respectively. Both Mx and COx were averaged and compared during the dissection phase, anhepatic phase, first 30 min of reperfusion, and remaining reperfusion phase. Impaired autoregulation was defined as Mx ? 0.4.Autoregulation was impaired in one patient during all phases of surgery, in two patients during the anhepatic phase, and in one patient during reperfusion. Impaired autoregulation was associated with a MELD score >15 (p = 0.015) and postoperative seizures or stroke (p < 0.0001). Analysis of Mx categorized in 5 mmHg bins revealed that MAP at the lower limit of autoregulation (MAP when Mx increased to ? 0.4) ranged between 40 and 85 mmHg. Average Mx and average COx were significantly correlated (p = 0.0029). The relationship between COx and Mx remained when only patients with bilirubin >1.2 mg/dL were evaluated (p = 0.0419). There was no correlation between COx and baseline bilirubin (p = 0.2562) but MELD score and COx were correlated (p = 0.0458). Average COx was higher for patients with a MELD score >15 (p = 0.073) and for patients with a neurologic complication than for patients without neurologic complications (p = 0.0245).These results suggest that autoregulation is impaired in patients undergoing liver transplantation, even in the absence of acute, fulminant liver failure. Identification of patients at risk for neurologic complications after surgery may allow for prompt neuroprotective interventions, including directed pressure management.

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Optimal blood pressure during cardiopulmonary bypass defined by cerebral autoregulation monitoring.

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Optimal blood pressure during cardiopulmonary bypass defined by cerebral autoregulation monitoring.

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