The Effect Of Different Anaesthetics On Remifentanil-induced Postoperative Hyperalgesia

Objectives:To assess the effect of maintenance anaesthetics (sevoflurane, pentobarbital, propofol) on postoperative pain in rats after remifentanil-based anesthesia and determine remifentanil induced-hyperalgesia of incision pain in rats whether is related to extracellular signal-regulated protein kinasel/2(ERK1/2) phosphorylation.Methods:Fifty-six adult male Sprague-Dawley rats in which caudal vein catheter was successfully placed were randomly divided into7groups (n=8):Group S (3%sevoflurane:induction and surgery;1.5%sevoflurane:maintenance), Group S+R(3%sevoflurane:induction and surgery;1.5%sevoflurane:maintenance; remifentanil1.5μg/kg/min), Group P (pentobarbital40mg/kg), Group P+R (pentobarbital40mg/kg, remifentanil1.5μωg/kg/min), Group Pro (propofol50mg/kg/h), Group Pro+R (propofol50mg/kg/h, remifentanil1.5μg/kg/min), Group HPro+R (propofol150mg/kg/h, remifentanil1.5μg/kg/min). All the rats underwent planter incision under the different anesthetic ways. Paw withdrawal threshold (PWT) and cumulative pain score (CPS) were measured24h before anesthesia and6h,24h,48h after anesthesia. The rats were sacrificed after the last threshold measurement. The expressions of ERK1/2phosphorylation in the left lumbosacral enlargement were assessed by western blot.Results:Compared with group S, the cumulative pain score (CPS) in incision paw of group S+R was significantly increased(P<0.05)in6h after drug withdrawal and the paw withdrawal threshold of both paws were significantly decreased(P<0.05) in24h after drug withdrawal. The cumulative pain score of the incision paw and paw withdrawal threshold of both paws in group P and group P+R were similar (P>0.05) in6h、24h、48h after drug withdrawal. Compared with group Pro and group Pro+R, the paw withdrawal threshold of the incision paw in group HPro+R was significantly increased (P<0.05) in6h,24h,48h after drug withdrawal. The cumulative pain score of the incision paw and paw withdrawal threshold of both paws in group Pro and group Pro+R were similar (P>0.05) in6h,24h,48h after drug withdrawal. Compared with group Pro+R, the cumulative pain score of the incision paw in group HPro+R was significantly decreased (P<0.05) in6h,24h,48h after drug withdrawal. The cumulative pain score of the incision paw in group HPro+R and group Pro were similar (P>0.05) in6h、24h、48h after drug withdrawal. The level of activated ERK1/2in group S+R is significantly increased (P＜0.001) among all the groups and the level of activated ERK1/2in group HPro+R is significantly decreased (P<0.001) among all the groups.Conclusions:Remifentanil can induce hyperalgesia in rats. Remifentanil induced hyperalgesia can be prevented by propofol and pentobarbital. ERK activation in spinal cord may play a role in remifentanil induced incision pain hyperalgesia and the anti-hyperalgesic effect of propofol and pentobarbital may be partly through suppressing the activation of spinal ERK.