Role of N-methyl-D-aspartate receptor antagonists as adjuvants to general anesthesia in postoperative analgesia

ABSTRACT

In the present study, postoperative pain was assessed in 48 patients undergoing elective abdominal surgery in the National Cancer Institute, Cairo University, with 3 different adjuvant medications; namely, saline [control group], magnesium sulfate [MgSO4] [group II] and low dose ketamine [group III] as physiologic NMDA receptor antagonists. After surgery, it was found that the time from the end of surgery to the first request for analgesia was longer in both [MgSO4] and ketamine group. Postoperatively, patients were treated with patient controlled analgesia [PCA] in exactly the same way. There was a statistically significant difference with reduced dose requirement of morphine in both MgSO4 and ketamine groups, compared with the control group after the operation. Mean visual analog scale [VAS] and verbal rating scale [VRS] were higher in patients of the control during the first 6 hours after surgery. Between 6 and 24 hours after surgery VAS and VRS were not significantly different. The results indicate that NMDA receptor antagonists could be of clinical interest as adjuvants to general anesthesia, as they were associated with smaller analgesic requirement than the control group in the postoperative period without adverse effects