Influence of Difference in Timing of Perioperative Administration of Low-dose Ketamine on Postoperative Analgesia

Preemptive analgesia is a part of multimodal regime for effective postoperative analgesia. Ketamine is said to possess preemptive effects, which has been simultaneously refuted by other studies. Hence, we designed this randomized, double-blinded trial to establish the influence of timing of perioperative ketamine administration for superior postoperative analgesia.

Ninety patients undergoing infraumbilical surgeries under spinal anesthesia were randomized to receive ketamine either preincision (Group KI), preincision and during skin closure (Group KII), or only during skin closure (Group KIII). Outcomes studied were postoperative pain, sedation, and incidence of side effects.

Analysis of variance statistics for postoperative visual analog scales (VAS) for pain showed no significant difference in three groups. However, there was a significant difference between Groups KII and KIII in the immediate postoperative period (95% confidence interval [CI] of mean VAS for Group KI = 0.9249-1.4889; 95% CI for Group KII = 1.4406-1.8260; P = 0.043). Sedation scores in the immediate, 4 h and 8 h postoperative showed a significant difference between Group KI and Group KII (P = 0.007, 0.008, 0.001, respectively) and between Group KI and KIII (KI: KIII - P = 0.0008, 0.0006, 0.02, respectively). Although the incidence of psychotomimetic effect was more in Groups KIII, it was not statistically significant.

Ketamine possesses postoperative analgesic effects in the immediate postoperative period only when its preemptive administration is supplemented with repeat administration during closure. Incidences of side effects were comparable in all groups.