Chronic AT1-receptor blockade does not alter cerebral oxygen supply/demand ratio during cardiopulmonary bypass in hypertensive patients.

Abstract

The angiotensin II receptor type 1 antagonist candesartan has been hypothesized to alter vasopressor requirements and brain-blood flow by changing cerebrovascular autoregulation. Therefore, we assessed the effects of a pre-anaesthetic treatment course with candesartan on cerebral arterial-jugular bulb oxygen content difference, middle cerebral artery blood velocity, and vasopressor requirements in hypertensive patients undergoing elective on-pump coronary artery bypass graft surgery. In a randomized, double-blind, placebo-controlled study, we evaluated the effects of candesartan (8 mg po/d, given for 6-8 days before surgery) in 35 hypertensive patients. The mean arterial pressure was maintained above 60 mmHg by bolus administration of phenylephrine, if required, and dosages were recorded. Candesartan did not significantly alter oxygen content difference across the cerebral circulation, mean middle cerebral artery blood velocity during cardiopulmonary bypass, or phenylephrine requirements either before (0.0067 microg/kg/min+/-0.0042 vs. 0.0056 microg/kg/min+/-0.0049, P=0.48) or during cardiopulmonary bypass (0.0240 microg/kg/min+/-0.0240 vs. 0.0250 microg/kg/min+/-0.0190, P=0.97) compared with placebo. Thus, a 6-8-day treatment course with candesartan does not alter global cerebral perfusion and oxygen supply/demand ratio during cardiopulmonary bypass, or vasopressor requirements in hypertensive patients undergoing on-pump coronary artery bypass graft surgery, and no deleterious consequences of AT1-receptor blockade were detected.