Intraoperative clonidine enhances postoperative morphine patient-controlled analgesia

Abstract

In this prospective study, the postoperative analgesic effects of intraoperative iv clonidine were evaluated. Two hundred consecutive patients undergoing major abdominal surgery were randomly assigned to either balanced anaesthesia with iv clonidine (Group 1)or balanced anaesthesia alone (Group 2). A PCA infuser was connected immediately after tracheal extubation. It was programmed to deliver morphine "on demand" iv boluses at doses of I mg for patients >65 yr and 1.5 mg for women or 2 mgfor men <65 yr old. A blinded observer assessed postoperative analgesia by recording the analgesic demands (both met and unmet), patient pain scores, sedation scores, and any side effects during the first 36 hr after surgery. Intraoperative clonidine reduced the number of analgesic demands during the observation period (45 ± 27 demands in Group 1 vs 81 ±60 in Group 2, P = 0.0001). This resulted in a reduction in morphine delivered (55.4 ± 30.6 mg vs 67.1 ± 45.1 mg, P < 0.05), mainly during the first 12 hr (19.7 ± 11.1 mg vs 27.6 ±18.1, mg P < 0.001) and the unmet demand rate was also reduced at all time intervals (P < 0.01). Clonidine did not exacerbate sédation or side effects. However, clonidine provided better analgesia in men and in patients <65 yr of age. Intraoperative iv clonidine enhances morphine analgesia after abdominal surgery. © 1992 Canadian Anesthesiologists.