The Influence Of Different Dosage Of Remifentanil On Postoperative Pain And Dose-response Relationship Of Tramadol For Inhibiting Remifentanil-induced Hyperalgesia

Obsjective 1 To investigate the phenomenon that intraoperative remifentanil administration results in opioid induced hyperalgesia.2 To investigate the dose-response relationship of tramadol for inhibiting postoperative hyperalgesia after remifentanil-based anesthesia.Methods This study was divided into two parts. Part one:Sixty patients aged 20-60yrs,ASAⅠ-Ⅱundergoing elective laparoscopic cholecystectomy were randomly allocated to three groups(n=20). Group A and group B were induced with remifentanil 1.5μg/kg,cisatracurium 0.2mg/kg and propofol 2mg/kg intravenous injection and group C was given fentanyl 3μg/kg replacement of remifentanil. After induction and tracheal intubation, group A and group B was maintained with remifentanil at 0.3μg/(kg-min) and 0.2μg/(kg-min) respectively, group C was maintained with fentanyl. Propofol was kept constantly intravenous injection and cisatracurium was injected intravenously according to the need of surgery. After patients recovered completely,the VAS pain scores were recorded after 15min,30min,1h,90min,2h,4h,8h of postoperative period.Part two:Sixty patients aged 20-60yrs,ASAⅠ-Ⅱundergoing laparoscopic cholecystectomy were randomly allocated to two groups(n=30):group AT[remifentanil 0.3μg/(kg·min)] and group BT[remifentanil 0.2μg /(kg·min)].Tramadol was used 5min before the beginning of the surgery for inhibiting remifentanil-induced postoperative hyperalgesia. Based on the 15th minutes'VAS postoperatively,up-and-down sequential experiment was used in.The dosage of tramadol was 0.8mg/kg iv for the first patient in both groups and the ratio of tramadol dosage between the two consecutive patients was 1.25.If it was effective(VAS<4),the dosage would be decreased for the second patient,if it wasn't effective(VAS>4), the dosage would be increased for the next patient. ED50 of tramadol was calculated according to Dixon and Massey.Results 1 Intraoperative hemodynamic responses and postoperative adverse reactions were similar in all groups.Group C had the longest recovery and extubation time and group A and group B were shorter(P<0.05). The time of requirement analgesia from extubation was significantly earlier and the cases of requirements analgesia were significantly more in group A and group B than group C. Postoperative VAS scores of group A and group B were significantly greater than that of group C and VAS score of group A was significantly greater than that of group B in the first 2 postoperative h(P<0.05).2 Tramadol's ED50 is 1.78 mg/kg,95%CI is 1.65mg/kg～1.93mg/kg in group AT.Tramadol's ED50 is 1.31 mg/kg,95%CI is 1.23mg/kg～1.39mg/kg in group BT.Conclusion 1 Remifentanil may induce withdrawl hyperalgesia after total intravenous anesthesia.2 Tramadol was used before the beginning of the surgery had significant suppressive effect on patients with remifentanil-induced postoperative hyperalgesia.