Effects of preincisional ketamine treatment on natural killer cell activity and postoperative pain management after oral maxillofacial surgery.

Poorly controlled pain may lead to increased risk of cancer metastasis by suppressing natural killer (NK) cell activity. Ketamine may be beneficial by potentiating opioid-induced analgesia. We enrolled 59 participants in a randomized double-blind, placebo-controlled clinical trial and assigned them to receive propofol plus (1) saline, 2 mL; (2) ketamine, 0.5 mg/kg; or (3) ketamine, 1.2 mg/kg, followed by a standardized anesthesia protocol. The visual analogue scale (VAS) and 24-hour opioid consumption measured postoperative pain perception. NK cell activity was measured before and 24 hours after ketamine administration using the chromium 51 release assay. Nonparametric analysis of VAS data revealed that women receiving 0.5 mg/kg of ketamine reported less pain (P <.05) compared with the saline 1.2 mg/kg-ketamine groups. This finding was not evident in men. Comparing opioid consumption among the 3 groups (using analysis of variance) revealed a drug-gender interaction (P < .05): 0.5 mg/kg of ketamine decreased postoperative opioid consumption for women more than for men. Although not statistically significant, women receiving 0.5 mg/kg of ketamine had the least NK cell suppression compared with preoperative values (repeated analysis of variance). These findings suggest that for women, low-dose ketamine may be beneficial.