Predicting the Limits of Cerebral Autoregulation During Cardiopulmonary Bypass

Abstract

Background-Mean arterial blood pressure (MAP) targets are empirically chosen during cardiopulmonary bypass (CPB). We have previously shown that near-infrared spectroscopy (NIRS) can be used clinically for monitoring cerebral blood flow autoregulation. The hypothesis of this study was that real-time autoregulation monitoring using NIRS-based methods is more accurate for delineating the MAP at the lower limit of autoregulation (LLA) during CPB than empiric determinations based on age, preoperative history, and preoperative blood pressure.

Risks for Impaired Cerebral Autoregulation During Cardiopulmonary Bypass and Postoperative Stroke

“…10 We found no relationship between patient age, history of diabetes, hypertension, or stroke and the MAP at the lower limit of autoregulation. Preoperative MAP did not accurately predict MAP at the autoregulation threshold; however, there was a relationship between systolic arterial pressure measured before surgery and the lower limit of autoregulation but only for patients with a systolic arterial pressure of ≤160 mm Hg.…”

Defining oliguria during cardiopulmonary bypass and its relationship with cardiac surgery–associated acute kidney injury

“…12 A continuous, moving Pearson's correlation coefficient between MAP and TCD blood flow velocity signals was then calculated to generate the variable mean velocity index (Mx). [8][9][10][11][12] When MAP is outside the limits of CBF autoregulation, Mx approaches 1, whereas it is close to 0 or negative when MAP is within the limits of autoregulation.…”

“…[8][9][10][11] Patients were eligible for enrolment if they were judged to be at high risk for stroke, as we have previously described. [8][9][10][11] Patients were excluded if they did not speak English, if they had visual impairment, or if there were contraindications to magnetic resonance imaging. The relationship between urine flow rate and MAP values below the lower limit of CBF autoregulation using this database has not been reported.…”

“…7 Our group has evaluated whether monitoring of cerebral blood flow (CBF) autoregulation provides a more precise approach for determining mean arterial pressure (MAP) targets during CPB than empirical targets. [8][9][10][11] We have found that the lower limits of CBF autoregulation vary widely between individuals and that the magnitude that MAP is below the lower limits of autoregulation influences the risk for AKI. [8][9][10]12 These findings indicate that the target MAP during CPB across individuals cannot necessarily be generalized and accurately empirically determined.…”

“…[8][9][10][11] We have found that the lower limits of CBF autoregulation vary widely between individuals and that the magnitude that MAP is below the lower limits of autoregulation influences the risk for AKI. [8][9][10]12 These findings indicate that the target MAP during CPB across individuals cannot necessarily be generalized and accurately empirically determined. Rather, an individualized definition of the lowest tolerable MAP based on physiologic end points, such as those derived from cerebral autoregulation monitoring, may better ensure organ perfusion during CPB, including that to the kidney.…”