Ketamine does not decrease postoperative pain after remifentanil-based anaesthesia for tonsillectomy in adults

Background: There are conflicting results concerning the pre-emptive effect of ketamine on central sensitization following surgery. The aim of this prospective, randomized, double-blind, placebo-controlled study was to assess the effect of the N-methyl-D-aspartate receptor antagonist ketamine on postoperative morphine consumption and pain score after remifentanil-based anaesthesia in adult patients scheduled for tonsillectomy. Methods: We studied 40 adult patients undergoing elective tonsillectomy. Total intravenous anaesthesia was induced and maintained with remifentanil (0.125-1.0 mug kg(-1) min(-1)) and propofol target-controlled infusion. Patients in group K received a bolus dose of ketamine 0.5 mg kg(-1) immediately after anaesthetic induction, followed by a continuous infusion of 2 mug kg(-1) min(-1). Saline was administered in the same sequence in group S. Propofol, remifentanil, and the study drug infusions were discontinued at the end of surgery. Results: Intraoperative remifentanil consumption (0.57 +/- 0.18 in group K vs. 0.55 +/- 0.14 mug kg(-1) min(-1) in group S), morphine requirement in the PACU (11 +/- 3 in group K vs. 9 +/- 4 mg in group S) and in the ward (22 +/- 11 in group K vs. 25 +/- 14 mg in group S), median time to first analgesia in the ward (338 +/- 126 in group K vs. 328 +/- 144 min in group S), and VAS pain scores were comparable in both groups. Conclusion: Small-dose of ketamine does not seem to be a useful adjunct to remifentanil-based anaesthesia during short, painful surgical procedures.