COMPARATIVE ANALYSIS OF THE EFFECT OF TWO DOSES OF INTRATHECAL MORPHINE INJECTION ON EXTUBATION TIME AFTER CORONARY ARTERY BYPASS GRAFTING

The object of the present study was to determine the effect of 2 doses of intrathecal morphine on extubation time and on postoperative analgestic requirements after coronary artery bypass graft surgery. This prospective, randomized, double blind placebo-control study was carried out on 60 adult patients(ASA II, ASA III) without emergency surgery, valvular heart disease, contraindication for spinal anesthesia or addiction. Patients (40-70 years old) were randomly divided to three groups to receive placebo, 3μg/Kg or 73μg/Kg interathecal morphine preoperatively. Intraoperative midozolame and fentanyl injection were limited to 153μg/Kg and 303μg/Kg intravenously. Patients were extubated in the intensive care unit by a blinded observer using predefined extubation criteria. Time to extubation and postoperative requirements for intravenous morphine was recorded by a blind observer. Patient in three groups did not have any significant difference in terms of age, weight or height. Extubation times were 465±207 minutes for placebo group and 414±245 minutes and 335±177 minutes for 3 μg/Kg & 7μg/Kg intrathecal morphine group(P=0.19). Postoperative morphine requirements in 3μg/Kg, 7μg/Kg and placebo groups were 18.8±7.8, 13.3±6.4 and 28.3±6.5(mg)(P=0.001). ABG analysis in three groups in ICU indicated that average Paco2 were 40.1±4.1, 43.6±6.5 and 47.9±4.8(mmhg) in placebo, 3μg/Kg and 7μg/Kg in intrathecal morphine groups respectively(P=0.001)(mean±SD). Despite decreased post operative morphine requirements, intrathecal morphine administration did not have a clinially relevant effect on extubation time after CABG surgery. This study suggests that 3μg/Kg intrathecal morphine is a suitable dose for providing significant postoperative analgesia without delaying tracheal extubation time and has minimum respiratory depression.