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

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 nitro-prusside 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 post-operative analgesia without delaying tracheal extubation. Copyright (C) 2000 by W.B. Saunders Company.