Analgesic effects of ketamine infusion on postoperative pain after fusion and instrumentation of the lumbar spine: a prospective randomized clinical trial.

BACKGROUND Intractable pain occurs as a result of extensive damage to soft tissue, bones and muscles after fusion of lumbar spondylolisthesis. Although different drugs and protocols have been suggested for postoperative pain management, the best method of treatment has not been proposed yet. Therefore, this study tried to compare the efficacy of ketamine infusion and routine opioid administration on postoperative pain. METHODS A double-blind prospective randomized clinical trial was performed on 45 patients candidate for fusion of lumbar spondylolisthesis. Patients were divided into two groups of A (treatment) and B (control). In group A, pain was controlled by intravenous infusion of ketamine. Morphine was also administrated when the patients scored their pain above 4 on a visual analogue scale (VAS). In group B, intravenous infusions of morphine were performed every 6 hours. VAS and whole dosage of morphine were compared between two groups every 6 hours. RESULTS Morphine and ketamine were both effective on pain control. Mean values of pain intensity at the first to fourth time points were 2.1, 1.8, 1.6, and 1.7 in group A and 3.9, 3.4, 3.5, and 3.5 in group B, respectively (p < 0.01 for all periods). However, ketamine was more efficient in pain reduction during the first 24 hours (p < 0.001). CONCLUSION Ketamine could be a good alternative analgesic after fusion of lumbar spondylolisthesis. However, the probable side effects should also be considered. Ketamine infusion is more effective than morphine on postoperative pain control. In addition, tolerance to drug application is not a challenging problem at least during 24 hours after operation.