Effect of subarachnoid morphine administration on extubation time after coronary artery bypass graft surgery

Abstract

Objective: To determine the effects of 2 low doses of intrathecal morphine on extubation time and on postoperative analgesic requirements after coronary artery bypass graft (CABG) surgery. Design: A prospective, randomized, double-blind, placebo-controlled study. Setting: Tertiary-care university hospital. Participants: Fifty adult patients scheduled for elective primary CABG surgery. Interventions: Patients were randomized to receive placebo, 250 μg, or 500 μg intrathecal morphine, preoperatively. Intraoperative fentanyl and midazolam were limited to 15 μg/kg and 20 μg/kg intravenously. Patients were extubated in the intensive care unit by a blinded observer using predefined extubation criteria. Measurements and Main Results: Time to extubation and postoperative requirements for morphine, midazolam, nitroglycerin, and sodium nitroprusside were recorded by a blinded observer. Extubation times were 441 ± 207 minutes versus 325 ± 188 minutes versus 409 ± 245 minutes for the placebo, 250-μg, and 500-μg groups (p = 0.27). Postoperative morphine requirements in the 250-μg and 500-μg groups were 13.6 ± 7.8 mg and 11.7 ± 7.4 mg, compared with 21.3 ± 6.2 mg in the placebo group (p = 0.001). There were no differences among the study groups with regard to postoperative midazolam, nitroglycerin, and sodium nitroprusside requirements. Conclusions: Despite decreased postoperative morphine requirements, intrathecal morphine administration did not have a clinically relevant effect on extubation time after CABG surgery. This study suggests that 250 μg is the optimal dose of intrathecal morphine to provide significant postoperative analgesia without delaying tracheal extubation. Copyright © 2000 by W.B. Saunders Company