Controlled Hypotension with Adenosine in Cerebral Aneurysm Surgery

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Abstract
The cardiovascular effects of adenosine-induced controlled hypotension were studied in 10 patients undergoing cerebral aneurysm surgery. Adenosine and its metabolites were measured in arterial plasma using high-pressure liquid chromatography. Whole body and cerebral arteriovenous O content differences (AVDO2), arterial lactate levels and arteriojugular lactate differences were determined. To reduce the dose requirement of adenosine, the patients were pretreated with the adenosine uptake inhibitor, dipyridamole (0.3-0.4 mg .cntdot. kg-1). During the infusion of adenosine(0.14 .+-. 0.04 mg .cntdot. kg-1 .cntdot. min-1) the mean arterial blood pressure decreased by 43%, from 82 to 46 mmHg, duing a mean hypotensive period of 32 min, without signs of tachyphylaxis. The arterial adenosine level increased from 0.15 .+-. 0.02 to 2.45 .+-. 0.65 .mu.M (P < 0.01). Hypotension was caused by a profound decrease in peripheral vascular resistance (61 .+-. 3%, P < 0.01), which was accompanied by an increase in cardiac output (44 < 9%, P < 0.01). Heart rate increased moderately by 16 .+-. 5% (P < 0.01). Pulmonary vascular resistance and central venous pressures were unaffected. Arterial lactate and Pa02 were unchanged, while whole body O2 consumption was decreased by 13 .+-. 4% (P < 0.05). The AVDO2 across the brain was decreased by 37 .+-. 5% (P < 0.05) without signs of lactate formation. Adenosine evidently rapidly induces a stable and easily controlled hypotension in humans by dilation of arterial resistance vasculature.