Low-dose ketamine with multimodal postcesarean delivery analgesia: A randomized controlled trial

Background: Ketamine at subanesthetic doses has analgesic properties that have been shown to reduce postoperative pain and morphine consumption. We hypothesized that intravenous ketamine 10 mg administered during spinal anesthesia for cesarean delivery, in addition to intrathecal morphine and intravenous ketorolac, would decrease the incidence of breakthrough pain and need for supplemental postoperative analgesia. Methods: Using a randomized double-blind placebo-controlled design, healthy women scheduled for cesarean delivery receiving hyperbaric spinal bupivacaine, fentanyl and morphine were randomized to intravenous ketamine 10 mg or saline following delivery. Postoperative analgesia included scheduled ketorolac and acetaminophen/ hydrocodone tablets as needed for breakthrough pain. The primary outcome was the incidence of breakthrough pain in the first 24 h. Secondary outcomes included the number of acetaminophen/hydrocodone tablets administered and numeric rating scale for pain (0-10). Results: Group characteristics did not differ. There was no difference in the incidence of breakthrough pain (ketamine 75% VS. saline 74%, P = 0.86). There was no difference in 24-h or 72-h use of supplemental acetaminophen/hydrocodone tablets between groups. Pain scores in the first 24 h were similar, but lower in the ketamine compared to the saline group 2 weeks postpartum (difference -0.6, 95% CI -1.1 to -0.9). Conclusions: We found no additional postoperative analgesic benefit of low-dose ketamine during cesarean delivery in patients who received intrathecal morphine and intravenous ketorolac. Subjects who received ketamine reported lower pain scores 2 weeks postpartum.