Cardiorespiratory response of intravenous angiotensin-converting enzyme inhibitor enalaprilat in hypertensive cardiac surgery patients

Abstract

Twenty-four patients undergoing elective coronary artery bypass surgery were studied. Either the angiotensin-converting enzyme (ACE) inhibitor enalaprilat, 0.06 mg/kg, ( n = 12), or saline solution (=control group; n = 12), was randomly and blindly administered intravenously when the mean arterial blood pressure (MAP) increased to 90 mmHg after induction of anesthesia. Cardiorespiratory parameters were studied before injection, during the subsequent 30 minutes, precardiopulmonary bypass (CPB), post-CPB, and at the end of surgery. MAP was significantly reduced 5 minutes after administration of enalaprilat. The peak reduction of blood pressure was observed after 30 minutes (from 98 ± 4 to 68 ± 8 mmHg). Even immediately before CPB (112 ± 12 minutes after injection of enalaprilat), MAP and systemic vascular resistance were significantly lower than baseline values. Heart rate remained almost unchanged in both groups. Cardiac index increased slightly in the enalaprilat patients (maximum: +0.75 L/min/m 2 20 minutes after injection). Filling pressures (central venous pressure, pulmonary capillary wedge pressure) were also significantly reduced by enalaprilat. There were no differences from the control patients with regard to changes in right ventricular hemodynamics (right ventricular ejection fraction, right ventricular end-diastolic volume, right ventricular end-systolic volume), pulmonary gas exchange (PaO 2), or intrapulmonary right-to-left shunting (Qs/Qt). VO 2 increased only in the enalaprilat patients (from 179 ± 28 to 230 ± 30 mL/min) ( p < 0.05). Cardiorespiratory parameters did not differ between the two groups post-CPB. No significant differences in the use of inotropes or vasoconstrictors were found during the entire investigation period. It is concluded that intravenous (IV) administration of the ACE inhibitor enalaprilat was effective in reducing blood pressure in patients with coronary artery disease with hypertension after induction with fentanyl/midazolam. Lack of a reflex increase in heart rate and reduction in left ventricular afterload indicated a decrease in myocardial oxygen consumption, which is of particular importance in coronary artery surgery patients. Improved tissue perfusion can be assumed because of the increase in oxygen consumption, whereas pulmonary gas exchange remained unchanged. Thus, IV enalaprilat enlarges the armamentarium for treating hypertension and can be recommended in patients with coronary artery disease undergoing cardiac surgery.