Impact of Cardiopulmonary Bypass Flow on Cerebral Autoregulation

Cerebral autoregulation is defined by the capacity of the brain to maintain a constant cerebral blood flow (CBF) despite variations of arterial pressure. However, when the arterial pressure is below a critical threshold, cerebral blood decreases.This critical threshold is called the lower limit of cerebral autoregulation (LLA).Cardiopulmonary bypass is a unique environment wherein systemic blood flow is totally controlled by the cardiopulmonary bypass pump. It has been shown that high pump flows combined with low arterial pressures did not compromise neurologic postoperative outcomes.Our hypothesis is that that LLA may depend on the cardiopulmonary bypass flow, ie the LLA may decrease when the cardiopulmonary bypass flow increases, explaining why low arterial pressure may be well tolerated.

Inclusion Criteria:Patient, male or female, over the age of 18Patient scheduled to undergo valvular heart surgery with planned CPBPatient with a Euroscore below 7%Patient affiliated or entitled to a social security schemePatient having received informed information about the study and having signed a free and informed consent to participate in the studyExclusion Criteria:Patient with untreated or uncontrolled severe hypertension despite treatmentPatient with chronic renal failure, with glomerular filtration < 30 mL/min/1.73m² or requiring a kidney transplantPatient with left ventricular ejection fraction < 40%Patient with a history of ischemic strokePatient having or about to benefit from renal vascular surgeryPatient with preoperative sepsisPatient who required a norepinephrine infusion within 24 hours before surgeryPatient presenting with an inaccessible temporal Doppler windowPatient candidate for emergency surgeryPregnant, parturient or breastfeeding womanPatient with preoperative uni or bilateral carotid stenosis > 50%Protected patient: adult under guardianship, curators or other legal protection, deprived of liberty by judicial or administrative decision