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

Abstract

Background: 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.

Methods: 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.

Results: 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.

Conclusion: 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.