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 ketamine 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 upper abdominal procedures.

INTERVENTIONS: Patients were randomly allocated to one of the two treatment groups: patients in Group 1 received epidural morphine 50 microg/kg whereas patients in Group 2 received epidural ketamine 1 mg/kg combined with 50 microg/kg of morphine postoperatively.

MEASUREMENTS: A blinded observer using a visual analog scale (VAS) for pain assessment followed up patients for 48 hours postoperatively. Top-up dose of epidural morphine was provided when VAS was higher than 4. Analgesic requirements and side effects were compared between the two groups.

RESULTS: Only 40 patients completed the study. There were no differences between the two groups with respect to age, gender, weight, duration, or type of surgical procedure or intraoperative opioid requirements. Onset of analgesia was faster (p < 0.001) in Group 2 (11 min) than in Group 1 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 required 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 sedation scores than Group I patients for the first 2 hours postoperatively. None 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 microg/kg improved analgesia after major upper abdominal surgery without increasing side effects.