Effects Of Dexmedetomidine On The Acute Hyperalgesia Induced By Remifentanil

Purpose:Dexmedetomidine is a highly selective a-2 agonist,can decreases central nervous system sympathetic outflow in a dose-dependent manner and has potent sedation and analgesic effects. The present study was designed to show the effects of dexmedetomidine with singl bolus infusion on the acute OIH induced by remifentanil.Mehtods:sixty adult (male and female 30 respectively)patients undergoing selective laparoscopic cholecystectomy were randomly assigned to three groups:Group DR,DF and CR. Before induction of anesthesia,patients in Group DR,DF received dexmedetomidine in loading dose of 1μg·kg-1 during a period of 10 minutes; and Group CR received normal saline instead. Then, induction and maintenance of anesthesia by routine protocol use different opioid analgesic(fentanyl,remifentanil) combine with propofol in different Group. At the end of operation, the time to awake (Ta, time of patient from drug withdrawal to reach OAA/S 5) will be recorded. The pain level was assessed by VAS scores,and initial dose of morphine 2mg will be given to patiens when the VAS scores reach 4,the initial Time of morphine administration (Tm) will be record, then 1mg morphine will be repeated every 2-3min to patients' satisfaction. The top scores of VAS, the doses of mophien for satisfactory analgesia and total doses of morphine in 4 hours also need to be recoded.Results:Ta in Group DF significantly longer than in Group DR and Group DR; Group DR significantly longer than Group CR; Tm of Group CR significantly shorter than Group DF and DR, Tm of Group DR shorter then Group DF. The top VAS scores of Group CR significantly higher than Group DF and DR, the score of Group DR also higher than Group DF, the difference was statistic significantly(P<0.01).The doses of morphine also highest in Group CR, the doses in Group DR also higher than Group DF, the difference was statistic significantly(P<0.01).Conclusion:Remifentanil induced acute hyperalgesia was indicated by VAS scores reach highest earlier, and the highest doses of morphine to maintenance satisfactory analgesia. Single bolus of Dexmedetomidine can attenuate the acute hyperalgesia induced by Remifentanil. But the effect of single bolus is limited, still need additional morphine to satisfaction.