Premedication with oral Dextromethorphan reduces intra-operative Morphine requirement

Intra-operative pain has adverse effects on hemodynamic parameters. Due to complications of opioids for pain relief, using non-opioids medication is preferred . The purpose of this study was to investigate the effect of oral dextrometorphan premedication on intra-operative Morphine requirement. Methods: After approval of the Ethics committee and informed consent, 40 adult patients who stand in American Society of Anesthesiologists Physical Status I and Il, under general anesthesia for elective laparatomy were selected and classified in two equal groups randomly. In group A, oral dextromethorphan (60mg) was administered at 10 PM and 6 AM preoperatively . In group B, placebo (dextrose) was administered. After induction of general anesthesia and before skin incision, intravenous morphine (0.01 mg/kg) was administered. During surgery, when systolic blood pressure or heart rate was increased more than 20% of the preoperative baseline, 0.01 mg/kg morphine was administered. At the end of surgery, the totally prescribed morphine (mglkg) and maximal increase in systolic, diastolic, mean arterial blood pressure and heart rate relative to the baseline values were calculated and statistically compared with student s t-test. Results: The mean dose of administered morphine during surgery was significantly less in group A than group B (P O.OOOl). Also, Maximal increase in systolic, diastolic and mean arterial blood pressure was significantly less in group A (p 0.003, p 0.004, p O.OOOl, respectively). There was no significant difference in maximal heart rate increase between two groups (p O.114). Conclusion: Oral dextromethorphan premedication may decrease intra-operative morphine requirement and reduce maximal increase in systolic and mean arterial blood pressure during surgery.