Comparison of epidural morphine and oxycodone for pain after abdominal surgery

To compare the efficacy and side effects of epidural morphine and oxycodone for pain following major abdominal surgery.

Randomized, double-blind study.

4th Department of Surgery, Helsinki University Central Hospital.

44 adult ASA physical status I, II, and III patients scheduled for elective major abdominal surgery.

Thirty-three patients were allocated randomly to one of two epidural groups and 11 patients received oxycodone intravenously (IV). The two epidural groups received either morphine (bolus 0.015 mg/kg followed by an infusion 0.003 mg/kg/hr) or oxycodone (bolus 0.15 mg/kg followed by an infusion 0.03 mg/kg/hr) before induction of standardized anesthesia and for 24 hours thereafter. A third group of patients was given the same dose of IV oxycodone as in the epidural group, serving as an open control group for epidural oxycodone.

Blood samples were drawn for plasma opioid concentrations. Postoperatively, pain (at rest and during coughing), nausea, pruritus, sedation, respiratory rate, and hemodynamics were recorded until the end of the infusions. The epidural dose ratio between morphine and oxycodone was 1:8.4 to 9.8 to provide similar analgesia. Side effects occurred similarly in the three groups. Mild respiratory depression was seen in all groups, especially in the IV oxycodone group. In all groups, hemodynamic variables remained within normal limits.

In the dosages reported, oxycodone can be used epidurally for acute post-operative pain. The analgesic effect was as good as that of epidural morphine.