The Effect Of Magnesium Sulfate Used On Remifentanil-induced Postoperative Acute Pain

Objective: To investigate the postoperative analgesic effect of magnesium sulfate used on remifentanil-induced acute opioid tolerance and hyperalgesia.Methods: A total number of forty ASAⅠ-Ⅱadult patients who undergoing major abdominal surgery were assigned randomly to tow anesthetic regimens. The magnesium group received magnesium sulfate 40mg/kg as a bolus five minutes before induction of anaesthesia and 10mg/kg/h by continuous intravenous infusion during the operation period. Each group was induced with propofol 2.5mg/kg, vecuronium 0.1mg/kg, remifentanil 2.0μg/kg intravenous injection and endotracheal. Aneasthesia was maintained with propofol (administered according to the bispectral index) and remifentanil (adjusted according to heart rate and arterial blood pressure) infusion. Vecuronium was administered 2mg every 30min and the last administration was 30min before the end of the surgery. After the operation, fentanyl was injected intravenously according to MAP, SBP, HR. Patient-controlled analgesia with a solution of fentanyl and ondansetron was used and the consumption of this solution was recorded. Pain scores and fentanyl consumption were recorded for 24 postoperative hours.Results: Patients in groupⅡrequired less remifentanil than those in groupⅠ[mean(sd)0.18(0.03)vs0.25(0.03)μg/kg/min,p<0.05] .The mean propofol infusion rate was(6.84±0.25)mg/kg/h in groupⅠis significantly greater than that in groupⅡ(5.35±0.31) mg/kg/h. Intraoperative hemodynamic responses were similar in each group. Postoperative pain scores were significantly greater in groupⅠ.These patients required fentanyl earlier than those in groupⅡ(P < 0.05), and fentanyl consumption was much more than those in groupⅡin the first 24 postoperative hours(P <0.05). Shivering incidents were significantly lower in groupⅡ(P<0.05).Conclusions: (1 )Intravenous magnesium sulfate could relieve the analgesia after operation and reduced the fentanyl consumption .These datas suggest that magnesium sulfate had significant suppressive effect on patient with postoperative hyperalgesia and acute opioid tolerance after remifentanil aneasthesia. (2)The administration of magnesium sulfate led to a significant reduction in requirements of remifentanil and propofol during total intravenous aneasthesia, and improved the quality of postoperative analgesia.