Evaluation of the safety and efficacy of epidural ketamine combined with morphine for postoperative analgesia after major upper abdominal surgery

Study Objective: To evaluate the efficacy of the combination of epidural ke tamine and morphine compared with epidural morphine alone for Postoperative pain relief following major upper abdominal surgery. Study design: Prospective, randomized, double-blinded study. Setting: Tertiary care referral and teaching hospital Patients: 46 ASA physical status I and II patients who underwent major uppe r abdominal procedures. Interventions: Patients were randomly allocated to one of the two treatment groups: patients in Group I received epidural morphine 50 mug/kg whereas p atients in Group 2 received epidural keta mine I mg/kg combined with 50 mug /kg of morphine postoperatively. Measurements: A blinded observer using a visual analog scale (IAS)for pain assessment followed up patients for 48 hours postoperatively. Top-up dose o f epidural morphine was provided when VAS was higher than 4. Analgesic requ irements and side effects were compared between the two groups. Results: Only 40 patients completed the study. There were no differences be tween the two groups with respect to age, gender, weight, duration, or type of surgical procedure or intraoperative opioid requirements. Onset of anal gesia was faster (p < 0.001) in Group 2 (11 min) than in Group I patients ( 25 min). The time for first requirement of analgesia was significantly (p < 0.01) longer (19.8 +/- 9.8 hours) in Group 2 patients than Group 1 (12.8 /- 6.2 hours). Total number of supplemental doses of epidural morphine requ ired in the first 48 hours postoperatively was also significantly less (p < 0.005) in Group 2 compared to Group 1. Patients in Group 2 had higher seda tion scores than Group I patients for the first 2 hours postoperatively. No ne of the patients in either group developed hallucinations or respiratory depression. Other side effects such as pruritus, nausea, and vomiting were also similar in both groups. Conclusions: The addition of epidural ketamine 1 mg/kg to morphine 50 mug/k g improved analgesia after major upper abdominal surgery without increasing side effects. (C) 2001 by Elsevier Science Inc.