Preemptive analgesic effect of ketamine in patients undergoing elective cesarean section.

OBJECTIVES

In this study, the preemptive effect of a small dose of ketamine on postoperative wound pain and morphine consumption in patients undergoing elective cesarean section was evaluated.

METHODS

In a randomized, double-blind clinical trial, 60 women with American Society of Anesthesiologists class I and II identification undergoing elective cesarean section were enrolled. In the case group, the patients received 0.5 mg/kg ketamine, and in the control group, they received isotonic saline, 5 minutes before the induction of anesthesia. Anesthesia was induced with 4 mg/kg thiopental followed by 1.5 mg/kg succinylcholine. A further neuromuscular block was achieved by using 0.2 mg/kg of atracurium. Anesthesia was maintained with nitrous oxide 50% and halothane in oxygen. The lungs were mechanically ventilated. After fetus delivery, fentanyl (2 microg/kg) and morphine (0.15 mg/kg) were given intravenously. In the postanesthesia care unit and in the ward, all patients received morphine. Pain was assessed by the Visual Analog Scales at 2, 6, 12, and 24 hours postoperatively; the amount of morphine used and side effects were recorded.

RESULTS

There was no significant difference between the patients considering their operative details, homodynamic variables, side effects, and Apgar scores of their babies at first and fifth minutes. Significantly, lower amounts of morphine were used in the case group (4.8 mg+/-2.5 mg vs. 8.1 mg+/-4.2 mg) during the first 2 hours after surgery (P=0.01), but the difference was not significant during 2 to 24 hours (3.2+/-2.2 vs. 3.1+/-2.3). There were no statistical differences between the groups in pain 2, 6, 12, and 24 hours postoperatively.

DISCUSSION

Intraoperative low-dose ketamine had no effect on morphine consumption during 2 to 24 hours after surgery. No significant differences were seen in the pain scores of the 2 groups during the study period. The preoperative administration of 0.5 mg/kg ketamine in patients undergoing cesarean section did not elicit a preemptive analgesic effect.