Effect of three different doses of ketamine prior to general anaesthesia on postoperative pain following Caesarean delivery: a prospective randomized study.

BACKGROUND: Ketamine is an analgesic suitable for the induction of anesthesia during Caesarean delivery. This double blind, randomized trial examined the effect of intravenous ketamine used before the induction of general anesthesia on morphine consumption, immediate and long term postoperative pain after Cesarean delivery.

METHODS: One hundred and forty term pregnant women undergoing elective Cesarean delivery were randomized into four groups (N.=35 each), placebo (0.9% normal saline), ketamine 0.25, 0.5, or 1 mg kg(-1) intravenously. In all patients 2-2.5 mg kg(-1) propofol was used for the induction of anesthesia, 0.6 mg kg(-1) rocuronium to facilitate the tracheal intubation and 50% oxygen in N2O and sevoflurane (end-tidal concentration of 1.2-1.3 %) for the maintenance of anesthesia. Postoperative analgesia was provided with intravenous morphine chloride patient-controlled analgesia (PCA) and rescue analgesia with intramuscular diclofenac sodium in the postoperative period. Apgar scores of the neonates and hemodynamic variables of the mothers were recorded during anaesthesia. Groups were compared regarding the cumulative morphine consumption and pain scores assessed with a numerical rating (0-10) scale at 2, 6, 12, 18, 24, and 48 h postoperatively. Postoperative side effects were recorded. Patients were evaluated for persistent postoperative pain at 2 weeks, 1 and 6 months, and 1 year.

RESULTS: The cumulative morphine consumption at 48 hours after the surgery was the primary outcome of the study. There was no significant difference in terms of acute pain at 2 (P=0.3), 6 (P=0.7), 12 (P=0.4), 18 (P=0.4), 24 (P=0.8), and 48 (P=0.5) hours postoperatively. Cumulative morphine consumption obtained at 2 (P=0.9), 6 (P=0.5), 12 (P=0.4), 18 (P=0.4), 24 (P=0.1), and 48 (P=0.2) hours was also similar among the groups. Prolonged postoperative pain evaluated 2 weeks (P=0.3), 1 month (P=0.7), 6 months (P=0.1) and 1 year (P=0.3) after the operation was also similar among the groups. There was no significant difference in side effects among the groups during the postoperative 48 hours. Apgar scores at 1 min (P=0.5) and 5 mins (P=0.5) were similar among the groups. Maternal intraoperative hemodynamic parameters were similar among the groups.

CONCLUSION: There was no difference regarding early and late postoperative pain and morphine consumption with ketamine at doses of 0.25, 0.5, and 1 mg kg(-1) in women undergoing Caesarean delivery under general anaesthesia, compared with the control group.