Effect of small dose ketamine on morphine requirement after intestinal surgery: A randomized controlled trial

Abstract

Background: N-methyl-D-aspartate (NMDA) receptors are thought to be for pain memory, and blocking them can help to reduce pain. We aimed to assess the preventive effects of small doses of ketamine administered prior to the skin incision in abdominal surgery, to assess analgesic efficacy and intra-operative and post-operative side effects. Methods: 60 adult patients with ASA I and II who were scheduled for abdominal surgery were randomly divided into two groups in a prospective, double-blind study. Before the skin incision, group K received 1 mg/kg ketamine intravenously, followed by a 0.12 mg/kg/h ketamine infusion till the skin was closed. Instead of ketamine, group C received normal saline. After extubation, both groups received morphine 5 mg IV. The visual analogue scale (VAS) was used to measure analgesic effectiveness at rest and after exercise, as well as the duration to the first analgesic and morphine intake in 24 h, and analyze changes in serum CRP and IL6 levels as indicators of its impact. Also, side effects of opioid or ketamine have been recorded. Results: Within 24 h, patients in the ketamine group had a significantly lower VAS score, a longer time to the first analgesic (326.3 ± 49.5 minutes), and lower morphine consumption (6.9 ± 2.91 mg). Also, postoperative interleukin 6 and CRP showed significant difference between the two groups (p ≤ 0.05). In group K, no side effects were detectable. Conclusion: Ketamine may be a promising drug in low doses that can limit and even prevent worsened inflammation. It also resulted in decreased postoperative opioid use, decreased pain rating, earlier retains of bowel motility, and decreased incidence of side effects.