Preemptive use of dextromethorphan for attenuation of tactile and thermal hyperalgesia associated with large dose remifentanil infusion

ABSTRACT

To determine the effect of I.M. 80mg Dextromethorphan on hyperalgesia induced by large dose remifentanil. Also to demonstrate the effect on postoperative opioid consumption, pain scores and stress response to surgery. Fifty patients ASA grade I and II undergoing abdominal hysterectomies under general anaesthesia were studied. The patients were allocated into one of two groups Large dose remifentanil group [LR]; receiving a dose of 0.4 micro g/kg/min and dextromethorphan remifentanil group [LRD]; receiving I.M. dextromethorphan 80mg + remifentanil 0.4 micro g/kg/min. Intravenous patient controlled analgesia [I.V. PCA] with morphine was initiated and maintained for 24 hours. Vital signs and pain were recorded and evaluated. Pain was assessed for 24 hours by visual analogue scale. The extent of thermal hyperalgesic areas were evaluated at the site of skin incision by testing the changes in cold and hot sensation using tip therm device. Tactile hyperalgesia was evaluated by the use of soft small brush, which was applied near the incision site and testing changes in touch sensation. Sedation level and morphine consumption were also assessed. Side effects were recorded and treated if happened. Demographic data were similar. Pain intensity was lower in dextromethorphan group. Thermal application revealed increase in the area of hyperalgesia to hot and cold stimuli around the surgical wound in large dose remifentanil when compared to large dose remifentanil dextromethorphan group. The soft brush induced less pain in large dose remifentanil dextromethorphan group [LRD] when compared to large dose remifentanil group. Postoperative morphine consumption by I.V-PCA was less in dextromethorphan group with decreased number of requests. Cortisol level was less in LRD group at 12 hours postoperatively indicating decreased stress response to surgery. Intramuscular administration of dextromethorphan decreased primary hyperalgesia induced by large dose remifentanil. Preemptive dextromethorphan resulted in a reduction of opioid consumption, pain scores and stress response to surgery with no related side effects