Postoperative morphine requirements for control of pain after nephrolithotomy under remifentanil based anesthesia; a comparison between preincisional or late intraoperative use of morphine

Pain control after surgical procedures is one of the most important concerns of anesthesiologists. Different schemes for postoperative pain management have been proposed including opioids. Short acting opioids like remifentanil cant completely achieve this goal (due to short duration of action and acute tolerance). The aim of this study is to compare the effect of the timing of morphine administration before skin incision or 20-30 minutes before end of surgery in nephrolithatomy patients with the aid of PCA. 60 patients, 40-70 years scheduled for nephrolithotomy with ASA Class I & II were included in a randomized, double – blind clinical trial study. Anesthesia was induced with propofol and remifentanil and maintained with propofol 75-100 μg/kg/min and remifentanil 0.1-0.5 μg/kg/min, 50% oxygen and 50% nitrous oxide. Morphine 0.1 mg/kg was given randomly to two equal groups at two different times during surgery: the first group before skin incision and the second, 20-30 minutes before completion of the procedure. Pain was evaluated in the postanesthetic care unit using a visual analogue scale score (VAS). The patient was sent to ward when the VAS score was 3. They were then checked for pain every 4 hours and finally the total amount of morphine used during the first postoperative day in each group was calculated. Hemodynamic changes, time to recovery, pain score, the amount of morphine used after awakening, time spent in recovery room and the total amount of morphine used in the first 24 hour and satisfaction were similar in both groups (p value> 0.05) The timing of intraoperative morphine administration didnt affect postoperative pain or total amount of morphine used postoperatively.