Lack of peripheral analgesic effect of low-dose morphine during intravenous regional anesthesia

To determine whether 1 mg morphine injected intravenously in conjunction with prilocaine has any effect on postoperative pain and analgesic requirement during intravenous regional anesthesia.

This was a randomized, double-blind study that included 37 patients undergoing carpal tunnel operations of the hand under intravenous regional anesthesia. Either 1 ml of morphine or 1 ml of physiologic saline diluted to 5 ml with 5% glucose was injected into the isolated exsanguinated arm. This was followed by 3 mg/kg of 0.5% prilocaine (total volume, 30-50 ml). Pain was assessed at 30, 60, 90, and 120 minutes, and 8, 24, and 48 hours after the end of the operation using a linear visual analog scale (VAS). The total number of analgesic tablets consumed in the first 48 hours were also counted.

No difference was found in the VAS pain scores between the groups at any of the time periods studied. The postoperative analgesic requirement was similar in both groups.

The authors conclude that 1 mg morphine showed no effect on postoperative pain or analgesic requirements when given in conjunction with prilocaine during intravenous regional anesthesia.