Angiotensin converting enzyme inhibition has no effect on blood pressure and splanchnic perfusion after cardiac surgery

Abstract

The purpose of this study was to study the effect of the angiotensin-converting enzyme inhibitor, enalaprilat, on blood pressure and splanchnic perfusion after cardiac surgery. Sixteen patients were studied after coronary artery bypass grafting. After admission to the intensive care unit, a 30-minute baseline measurement of systemic hemodynamics, oxygen transport, and gastric tonometry was performed. In 6 of 10 patients receiving enalaprilat and in each of 6 control patients, regional (splanchnic and leg) blood flows were measured also. After the baseline measurement period, 10 patients received a 0.5 mg bolus of enalaprilat and thereafter an incremental infusion of enalaprilat up to a total dose of 10 mg (mean 8.3; range 4 to 10 mg) was continued to reduce the mean arterial pressure (MAP) to 70 to 80 mm Hg. A 30-minute measurement period was repeated 2 to 3 hours after the first measurement period. In the control group, the second measurement was performed at corresponding time points. Though MAP decreased in the enalaprilat group (enalaprilat 99 +/- 14 mm Hg v 89 +/- 21 mm Hg, P < .05; control 95 +/- 13 mm Hg v82 +/- 10 mm Hg, P = NS) in only 4 of 10 patients was the targeted MAP reduction achieved. No significant changes were observed either in systemic or regional blood flows. Systemic, pulmonary, and femoral vascular resistance indices decreased significantly in both groups. Gastric-arterial PCO2 difference did not change in either groups. Angiotensin-converting enzyme activity decreased in the enalaprilat group (10.0 +/- 2.3 v 1.3 +/- 0.3 U x l(-1), P < .01), but plasma renin and endothelin-1 concentrations did not change in either group. The effect of enalaprilat on blood pressure was poor and it had no beneficial effects on splanchnic circulation. Renin-angiotensin activation is not a major factor in hypertension and splanchnic perfusion after cardiac surgery.