Infiltration of morphine into an abnormal wound; effects on pain relief and endocrine/immune response

We wanted to evaluate pain relief and endocrine/immune response after local administration of morphine into an abdominal wound. In a randomised double blind design 29 patients undergoing hysterectomy received two blinded injections of morphine and saline. Before surgery the patients in the control group (n = 15) got 10 mg of subcutaneous morphine into an arm and at skin incision 30 ml of saline was infiltrated directly into the wound. The patients in the wound group (n = 14) received 1 ml of saline into an arm before surgery and 10 mg of morphine in 30 ml of saline into the wound at skin incision. Patient controlled analgesia (PCA) with i.v. morphine was used after surgery. Repeated blood samples were obtained from the day before the surgery until 3 days later and analysed for cortisol and interleukin-6 (IL-6). There were no differences between the groups either in pain relief or in the consumption of PCA morphine. The wound group used 47 +/- 15 mg of i.v. morphine and the control group used 50 +/- 16 mg. Peak values for IL-6 and cortisol appeared at 4 h. The area under the curve (AUC) of cortisol at 0-6, 0-10 and 0-20 h was significantly lower in the control group than in the wound group (P < 0.05). High doses of i.v. morphine reduced cortisol and IL-6 levels in the early hours after surgery. The injection of morphine into the wound did not improve pain relief or reduce the consumption of i.v. morphine after surgery. The endocrine stress response to trauma was modified by preoperative administration of morphine.