A Comparison of Ketamine and Paracetamol for Preventing Remifentanil Induced Hyperalgesia in Patients Undergoing Total Abdominal Hysterectomy

Background: The aim of this prospective, randomized, placebo-controlled study was to compare the effects of ketamine and paracetamol on preventing remifentanil induced hyperalgesia. Methods: Ninety patients undergoing total abdominal hysterectomy were randomly assigned to one of three groups to receive (I) either saline infusion; (II) 0.5 mg/kg ketamine iv bolus or (III) 1000 mg iv paracetamol infusion before induction of anesthesia. Until the skin closure, anesthesia was maintained with 0.4 µg/kg/min remifentanil infusion in all groups, additionally Group II received 5 µg/kg/min ketamine infusion. Pressure pain thresholds were measured the day before surgery during the preoperative visit for baseline measurements and repeated postoperatively at 24 and 48 hours (hrs). Pressure pain thresholds were established by digital algometer on three different peri- incisional regions for calculating mean pressure pain threshold values. The visual analogue scale (VAS), sedation scores, total morphine consumption and side effects were assessed postoperatively. Results: Demographic characteristics, duration of surgery and anesthesia were similar in the three groups. Pain thresholds at the incision region were significantly lower at 24 and 48 hrs postoperatively in Group I than the other Groups (p< 0.05). In Group І, pain thresholds were lower compared with preoperative baseline values. Thresholds in Group ІІ and Group ІІІ were higher compared with preoperative baseline values (p< 0.05) The VAS scores at all evaluation times were significantly higher in Group І when compared to Group ІІ and at 2, 4, 6 ,12 hrs were higher in Group I than Group ІІІ (p< 0.05). The morphine consumption was higher in Group ІІІ at 24 and 48 hrs postoperatively (p< 0.05). Conclusion: It was shown that ketamine and paracetamol were both effective in preventing remifentanil induced hyperalgesia.