Effects of dextromethorphan on postoperative pain after orthopedic surgery under spinal anesthesia

Abstract

Summary Purpose Previous studies showed that pre-incisional administration of dextromethorphan (DM), a weak N-methyl-D-aspartic (NMDA) acid antagonist, reduces postoperative pain after epidural as well as general anesthesia. Aim of this study was therefore to proof the effects of DM on postoperative pain in patients undergoing orthopedic surgery under spinal anesthesia. Methods Forty-five patients undergoing elective orthopedic surgery were enrolled in this prospective, double-blinded and randomized study. Patients were randomly assigned to three groups (n = 15) and received either placebo or dextromethorphan (45 or 90 mg) p.o. Afterwards, a spinal catheter was inserted at the L2/3 or L3/4 interspace and spinal anesthesia with bupivacaine was induced and maintained at a level between Th 10 and Th 12. After completion of surgery patient controlled analgesia (PCA) with piritramide was started. Visual analogue pain scales (VAS) and analgesic requirements were assessed before surgery (control) as well as during the first 48 hours. Results The three groups were comparable with respect to biometric data, distribution of surgery as well as preoperative pain levels. VAS scores were not different between the three groups within 48 hours postoperatively. Furthermore, administration of pre-incisional DM had no influence on postoperative requirements of opioids (group D90: 59.5 ± 37.5 mg; group D45: 56.2 ± 37.1 mg piritramide; and group P: 49.3 ± 29.2 mg piritramide) within 48 hours. Conclusions In this study DM enables neither reduction of postoperative pain intensity nor analgesic- or opioid-sparing effects. Further studies to find out ideal dosage, way of administration and applicable kind of surgery should be implemented.