Preincisional dextromethorphan treatment for postoperative pain management after upper abdominal surgery

Previous studies showed that ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist, provides a preemptive analgesic effect and preemptive analgesia improves postoperative pain management. The aim of this study was to examine whether premedication with dextromethorphan (DM) improves postoperative pain management after upper abdominal surgery. Sixty (American Society of Anesthesiologists class 1 and 2 of either gender) patients scheduled for upper abdominal surgery were included in the study. Patients were randomly assigned to one of four groups: control, DM-10, DM-20, and DM-40. In the control group, chlorpheniramine maleate (CPM, 20 mg) was injected immediately before induction of anesthesia intramuscularly (IM). In the DM-10, DM-20, and DM-40 groups, patients were premedicated with DM 10 mg, 20 mg, and 40 mg IM, respectively. After operation, patient-controlled analgesia (PCA) with morphine was given for pain relief. The time to the first PCA trigger, morphine consumption, pain scores, and analgesic-related side effects were recorded at 1, 2, 4, 24, 48, and 72 hours after surgery. The time to first PCA trigger for the control group was 17.8 +/- 1.4 minutes, for group DM-10 20.2 +/- 1.6 minutes, for group DM-20 32.4 +/- 1.9 minutes, and for DM-40 77.9 +/- 6.5 minutes. The morphine delivered and PCA triggering frequency were 5.5 +/- 0.5/11.3 +/- 0.8 times for the controls, 5.5 +/- 0.4/ 14.1 +/- 1.3 times for DM-10, 3.1 +/- 0.3/6.3 +/- 1.2 times for DM-20, and 0.2 +/- 0.1/0.3 +/- 0.2 times for DM-40 during the first hour after operation. For the first day, the figures are 19.9 +/- 1.2/23.9 +/- 1.4 for the controls, 15.6 +/- 1.2/17.3 +/- 2.4 for DM-10, 12.6 +/- 0.7/15.9 +/- 1.6 for DM-20, and 5.0 +/- 0.21/5.6 +/- 0.9 for DM-40. On the first day, the cough pain scores were 6.67 +/- 0.23, 6.53 +/- 0.16, 6.67 +/- 0.23, and 5.73 +/- 0.18 for the controls, DM-10, DM-20, and DM-40 groups, respectively. All data showed dose-dependent better pain relief in DM-premedicated patients. We conclude that DM premedication offers preemptive analgesia and reduces postoperative pain and morphine requirement.