ORAL PREMEDICATION ENHANCES THE POSTOPERATIVE ANALGESIA BY EPIDURAL MORPHINE

Abstract

S338 INTRODUCTION: It is controversial whether preoperative clonidine administration reduces postoperative morphine requirements [1,2]. We have previously reported that oral clonidine premedication potentiates postoperative analgesia from intrathecal morphine [3]. This study was designed to prospectively assess the effect of oral clonidine premedication on postoperative analgesia by epidural morphine. METHOD: After institutional approval, 56 consented patients, undergoing gynecological surgeries, were randomly assigned to one of three groups; Clonidine-Morphine group (n=19) received oral clonidine 5 mcg/kg 90 min before arriving at the operating room and epidural morphine 2 mg, Placebo-Morphine group (n=20) received no clonidine and epidural morphine, Clonidine-Placebo group received clonidine and no epidural morphine. Epidural catheters were placed at L1-2 or L2-3 interspace, and tested with 3 ml 1.5 % lidocaine containing 15 mcg epinephrine followed by 12 ml 1.5 % lidocaine solution with or without 2 mg morphine. General anesthesia was induced with propofol and maintained with 67 % nitrous oxide and propofol. Lidocaine 10 ml was injected into the epidural space every hour without any other analgesic. After surgery, IV-PCA morphine was started (no continuous infusion, PCA bolus dose of 2 mg morphine, lockout interval of 10 min, maximal 1 hour dose of 12 mg). Postoperative pain was evaluated using the VAS at 1, 6, 12, 18, 24, 36 and 48 h. Nausea and pruritus were also assessed at the same interval. Unpaired Student's t-test and Mann-Whitney U-test were used for data analysis. P<0.05 was considered statistically significant. RESULTS: The three groups were similar in terms of age, height, weight, duration of surgery and doses of lidocaine. Cumulative morphine requirements in the Clonidine-Morphine group were significantly less than the other two groups (Figure 1). VAS scores in the Clonidine-Morphine group were lower than the Placebo-Morphine group at 48 h at rest, and also were lower than the Placebo Morphine group at 1, 24, 36 and 48 h at moving. There were no significant differences in the incidence of nausea and pruritus among groups.Figure 1: Cumulative morphine doses in the Clonidine-Morphine group were less than those in the Clonidine-Placebo group throughout study period and than those in the Placebo-Morphine group from 20 to 48 h. * P < 0.05 vs the Placebo-Morphine group.CONCLUSION: Our results suggest that oral clonidine premedication enhances postoperative analgesia by epidural morphine.