The effect of pre-anaesthetic administration of intravenous dexmedetomidine on postoperative pain in patients receiving patient-controlled morphine

Abstract

This prospective, randomized, double-blind, controlled study was designed to test the effect of pre-anaesthetic administration of dexmedetomidine, given as a single intravenous (i.v.) dose, on postoperative pain scores and morphine consumption in patients receiving patient-controlled morphine after abdominal surgery. Sixty patients were randomly allocated to receive dexmedetomidine (1 microg kg(-1)) or saline 10 min before induction of anaesthesia. Twenty minutes before the end of surgery, all patients received a standardized (0.1 mg kg(-1)) loading dose of morphine. They were then allowed to use a patient-controlled analgesia (PCA) device giving bolus doses of morphine (0.02 mg kg(-1)). Pain, discomfort and sedation scores; cumulative morphine consumption; time to extubation; time to recovery; and any side-effects were recorded after recovery and at 1, 2, 6, 12 and 24 h after the start of PCA. The mean time to extubation at the end of anaesthesia and recovery time were similar in both groups. There were no significant differences between groups with regard to mean pain, discomfort, sedation and nausea scores. Cumulative morphine consumption was significantly lower in the dexmedetomidine group at 6, 12 and 24 h (P < 0.05). The incidence of side-effects did not differ between the groups. A single i.v. dose of dexmedetomidine (1 microg kg(-1)) given 10 min before induction of anaesthesia significantly reduced postoperative morphine consumption at identical pain scores compared to control, but had no effect on postoperative recovery time.