Background: Most postoperative upper abdominal pain is severe, and various methods can be employed to control it. Presently, morphine is the main drug used for anesthesia, but it may contribute to the occurrence of many uncomfortable side effects. Ketamine is an analgesic drug that inhibits NMDA receptors, making it a synergistic effect of morphine.

Objective: To investigate the efficacy of a combination of ketamine and morphine in controlling postoperative upper abdominal pain.

Materials and Methods: Informed consents were obtained from patients enrolled into the present double-blind randomized study that divided into two groups, (i) the M group, which received 1 mg/mL of morphine, and (ii) the MK group, which received 1 mg of ketamine plus 1 mg/mL of morphine as intravenous patient-controlled analgesia (IV-PCA) post-operation. All patients were assessed based on postoperative morphine consumption, a numeric rating scale (NRS) used to rate pain, and the presence of side effects.

Results: Sixty-seven patients completed the study including 34 patients in the MK group and 33 patients in the M group. Cumulative postoperative morphine consumption at 24 and 48 hours was significantly lower in the MK group at 27.91±11.11 and 46.44±15.21 mg compared to the M group at 43.24±15.32 and 71.33±19.67 mg, respectively (p<0.001). NRS were similar between the two groups and no observable differences regarding to side effects.

Conclusion: A combination of ketamine and morphine via IV PCA is effective in controlling postoperative upper abdominal pain.