Comparison of isoflurane and midazolam as hypnotic supplementation to moderately high-dose fentanyl during coronary artery bypass grafting: Effects on systemic hemodynamics and early postoperative recovery profile

Objective: The aim of this study was to compare isoflurane and midazolam as hypnotic adjuncts to moderately high-dose fentanyl during coronary artery bypass grafting (CABG) with regard to perioperative hemodynamics and early postoperative recovery profile. Design: Prospective open randomized clinical trial. Setting: Single university-affiliated medical center. Participants: Thirty patients scheduled for elective primary CABG were randomly divided into two groups receiving either isoflurane or midazolam as adjuncts to 50 mu g/kg of fentanyl. Intervention: Anesthesia was induced with intravenous fentanyl, 10 mu g/kg, and midazolam, 0.1 mg/kg, and maintained with either isoflurane, 0.6%, or midazolam, 0.1 mg/kg/hour, in intravenous infusion. Before the sternotomy, all patients received 30 mu g/kg of fentanyl. Midazolam and isoflurane were stopped at the start of cardiopulmonary bypass (CPB). At rewarming, all patients received fentanyl, 5 to 10 mu g/kg, and either isoflurane, 0.6%, or midazolam, at a reduced rate of 0.05 mg/kg/h. Changes in systolic blood pressure of more than 20% from baseline were first treated with vasoactive drugs. Hypertension was corrected with ketanserin, 10 to 20 mg; hypotension with ephedrine, 5 mg. For a mean blood pressure of less than 50 mmHg during CPB phenylephrine, 0.25 to 0.5 mg, was administered. When hypotension persisted despite a vasopressor, the administration of midazolam or isoflurane was stopped. Postoperatively, the patients were mechanically ventilated overnight and sedated with intermittent doses of fentanyl, 0.15 mg, and midazolam, 5 mg. Measurements and Main Results: Routine five-lead electrocardiogram (ECG) and invasive hemodynamic monitoring using a pulmonary artery catheter were performed. The mean dose of fentanyl was 3.9 mg in the midazolam group versus 3.6 mg in the isoflurane group. There were no significant perioperative differences between groups in cardiac output, filling, or pulmonary artery pressures. Systolic blood pressure from the initial incision to CPB was lower in the isoflurane group compared with the midazolam group. During this interval, ketanserin was required in nine patients from the midazolam group at a mean dose of 26 mg, compared with only one patient in the isoflurane group. During and after CPB, there was no difference in ketanserin and in vasopressive/inotropic agent requirements. Temporary cessation of midazolam was required in four patients, far a mean of 34 minutes; whereas isoflurane was stopped in 10 patients for 36 minutes, mostly in the post-CPB period. Time to awakening and to extubation in the midazolam group (217 minutes and 19.5 hours) and the isoflurane group (193 minutes and 18.2 hours) were comparable. Between intensive care unit (ICU) admission and extubation, the patients in the midazolam group received 0.89 mg of fentanyl and 36.5 mg of midazolam compared with 0.98 ntg of fentanyl and 36.2 mg of midazolam in the isoflurane group. There was a tendency for a higher postoperative pulmonary shunt: and more severely impaired oxygenation in the isoflurane group. Conclusion: Midazolam supplementation to fentanyl required more frequent antihypertensive escape during the pre-CPB period than isoflurane. However, more frequent cessation of isoflurane caused by hypotension was needed in the post-CPB period. No difference in awakening and ICU discharge was found. Copyright (C) 1997 by W.B. Saunders Company.