Clinical benefits related to the combination of ketamine with morphine for patient controlled analgesia after major abdominal surgery

Abstract

Background: combination of ketamine may improve morphine patient controlled analgesia (PCA) but clinical results are still equivocal.

Aim: The authors designed a powerful study to evaluate this hypothesis after major abdominal surgery.

Methods: 138 patients undergoing abdominal surgery participated in the randomized double blind study. Patients were allocated to two groups: M-group: morphine 0.5 mg/ml + placebo in PCA and MK-group: morphine 0.5 mg/ml + ketamine 0.5 mg/ml with the same bolus dose and lock out time. The patients were evaluated during 48 hours by visual analog scale (VAS), simplified verbal scale (SVS). Side effects and amount of morphine used were monitored.

Results: The two groups are comparable for demographic data and surgery characteristics. From the 24th hour, morphine consumption was significantly lower in the MK-group. At 48 hours after surgery, the amount of morphine received in the MK-group was significantly lower than in the M-group (48 vs 66 mg, p < 0.001). The average value of VAS was lower in the MK-group from the 12th hour at rest and 20th hour during mobilization. SVS was significantly lower for the MK-group after the 12th postoperative hour. The incidence of respiratory depression was higher in the M-group: 4 vs none in the MK-group. The incidence of nausea, vomiting and pruritus was halved in the MK-group (p < 0.04).

Conclusion: The combination of ketamine with morphine in PCA after major abdominal surgery offers a reduction of the morphine consumption, a reduction of pain scores and a decrease in the incidence of adverse effects.