Efficacy of different low-doses of nalmefene in preventing remifentanil-induced postoperative hyperalgesia

Abstract

Objective To evaluate the efficacy of different low-doses of nalmefene in preventing remifentanil-induced postoperative hyperalgesia. Methods One hundred American Society of Anesthesiologist physical status Ⅰor Ⅱpatients, aged 20-64 yr, wih body mass index of 18-25 kg/m2, scheduled for elective gynecological laparoscopic surgery under general anesthesia, were divided into 4 groups(n=25 each)using a random number table: control group(group C)and different doses of nalmefene groups(N1, N2 and N3 groups). In N1, N2 and N3 groups, nalmefene 0.2, 0.3 and 0.5 μg/kg(diluted to 5 ml in normal saline)were intravenously injected, respectively, at 5 min before anesthesia induction, while the equal volume of normal saline was given in group C. Anesthesia was induced with midazolam 0.05 mg/kg, sufentanil 0.3 μg/kg, etomidate 0.3 mg/kg and rocuronium 0.6 mg/kg.The patients were mechanically ventilated after tracheal intubation.Anesthesia was maintained by IV infusion of remifentanil 0.3 μg·kg-1·min-1 and inhalation of 4%-6% desflurane, bispectral index value was maintained at 45-60, and muscle relaxation was maintained with intermittent IV boluses of rocuronium.After admission to postanesthesia care unit, patient-controlled analgesia(PCA)was performed, and PCA solution contained sufentanil 1 μg/ml in 100 ml of normal saline.PCA pump was programmed to deliver a 0.5 ml bolus dose with a lockout interval of 15 min and background infusion at 2 ml/h.Numeric rating scale score was maintained <4.The time for remifentanil infusion was recorded.The consumption of sufentanil was recorded in 0-1, 1-3, 3-6, 6-12 and 12-24 h periods after surgery, and the occurrence of nausea, vomiting, tachycardia, hypertension and shivering was also recorded within 24 h after surgery. Results Compared with group C, the postoperative consumption of sufentanil was significantly reduced in 0-1 h and 1-3 h periods after surgery in group N1 and in 0-1, 1-3, 3-6 and 6-12 h periods after surgery in group N2, and the incidence of postoperative nausea was significantly decreased in N1, N2 and N3 groups(P<0.05). The consumption of sufentanil in 3-6 h period after surgery was significantly lower in group N2 than in group N1(P<0.05). Conclusion The optimal dose of nalmefene is 0.3 μg/kg when used to prevent remifentanil-induced postoperative hyperalgesia. Key words: Morphinane; Piperidines; Hyperalgesia