Effects Of Intraoperative Dexmedetomidine Infusion On Postoperative Pain And Remifentanit-induced Hyperalgesia After Remifentanil-sevolfurane Anaesthesia

Objective:To investigate the influence of intraoperative Dexmedetomidine infusion onpostoperative pain and remifentanil-induced hyperalgesia.Method:Seventy-five patients （ASAⅠorⅡ） scheduled for laparoscopic cholecystectomyand biliary passage exploration were randomly divided into three groups:Small-doseremifentanil（SR group）, high-dose remifentanil（HR group）, high-dose remifentaniland dexmedetomidine（RD group）. teach patients and their families to use visualanalogue score（VAS） and patient controlled intravenous analgesia（PCIA） beforeoperation. After induction of anesthesia, patients in group RD were givendexmedetomidine via vein at0.5μg^-1kg^-1h-1,patients in group SR and group HR weregiven saline at0.5μg^-1kg^-1h-1. Group HR and group RD were given intravenousinfusion of0.3μg^-1kg^-1min-1remifentanil, Group SR was given intravenous infusionof0.1μg^-1kg^-1min-1remifentanil. Three groups inhaled sevoflurane to maintainanesthesia, keep the BIS from40to60and PETCO2from35to45mmHg. All patientswere given a bolus of1μg/kg fentanil10min before the end of surgery. After thesurgery, the patients were placed in post anesthesia care unit（PACU） for2h afteroperation. After patients recovered completely, they or nurses controlled their fentaniladministration by push the button of patient controlled intravenous analgesia pump.The pain scores and Ramsay scores were evaluated every10min after awake inpostanesthesia care unit, and then the scores at30minth,60minth,90minth,2hth,4hth,6hth,12hthand24hthof postoperative period were recorded. Fentanil consumption wasrecorded for24postoperative hours.Result:From patients awakeness to the following90min in PACU, the VAS scores ofgroup HR were significantly increased than other two groups. Compared with groupHR, in SR and RD groups,the score when the patient’ s first VAS≥4weresignificantly smaller （P＜0．05）, the time to VAS＜4was shorter（P＜0．01）, the PCIA consumption in PACU decreased （P＜0．01）, the times of using PCIAby patients themselves decreased by24thh in the ward（P<0.01）; the awareness timeand the extubation time were similar in all groups; the Ramsay scores of RD werehigher than HR group （P＜0．05）, however, they were similar in group SR andgroup RD.Conclusion:Based on our results, we demonstrated that a high dose of remifentanil mayinduce withdrawl hyperalgesia and/or clinically acute opioid tolerance.however,Intraoperative Dexmedetomidine infusion can effectively relieve postoperative pain,reduce postoperative analgesic requirements and alleviate remifentanil-inducedhyperalgesia without affecting the anesthesia revival.