The Effect Of Dexmedetomidine On Baroreflex Sensitivity During General Anesthesia

Part One:Animals Research-The effect of dexmedetomidine on arterial baroretlex function in ratsObjective:This study was designed to investigate whether dexmedetomidine improve the depressed arterial baroreflex function of the rats anaesthetized with propofol by observing the effect on arterial baroreflex function of rats.Methods:Research One:18 male SD rats were randomly divided into three groups, N1 group (Dex 1μg/kg), N2 group (Dex 3μg/kg), N3 group (Dex 10μg/kg). Blood pressure, heart period (HP) and baroreflex sensitivity (BRS) were measured in the three groups, recorded as BRS0. After intravenous of Dex, mesured the three parameters again, recorded as BRS1.Research Two:12 SD rats were randomly divided into two groups, P group and D group, the baseline BRS level were measured, and recorded as BRS0. In group P, after the use of propofol 10 mg/kg, the BRS were measured again, and record as BRSi. While in group D, the use of propofol 10 mg/kg was delayed 10 min after the use of Dex 3μg/kg slowly, and then the BRS were measured again, and record as BRS1.Results:There were no significant differences in BRS in group N1, N2 and N3 after the treatment of Dex. In group P, BRS1 decreased significantly than BRS0. Compared with BRS0, no significant difference of BRS1 was found in group D, and BRS1 in group D were significantly higher than that m group P.Conclusions:Dexmedetomidine does not affect BRS of SD rats which with normal ABR. While dexmedetomidine improves the depressed baroreflex function of rats anesthetized with propofol.Part Two:Clinical Study-The effect of dexmedetomidine on arterial baroreflex function during general anesthesiaObjective:This study was designed to investigate the effect of dexmedetomidine on arterial baroreflex function in patients undergoing general anesthesia.Methods:72 patients were accepting elective breast lumpectomy undering general anesthesia, and 60 patients completed this study finally. The patients were randomly divided into two groups (n=30), Dex group with Dex 0.5μg/kg, then 0.4μg kg-1 h-1 after 10 min until the end of surgery. Con group with an equal volume of saline. All patients were anaesthetized with propofol 2 mg/kg, sufentanil 0.5μg/kg and rocuronium 0.6 mg/kg. After loss of consciousness, the laryngeal mask were placed, patients’lungs were ventilated mechanically. Anesthesia was maintained with propofol and remifentanil. BRS and hemodynamic parameters were measured using Finapres Medical Systems for 5 minutes. Finapres parameters were obtained at the four periods: when patients were calmed down after entering the operating room (T1), after the 10-minutes Dex or saline bolus infusion (T2),5 min after placing the laryngeal mask (T3), and 5 min after the start of operation (T4). The use of vasoactive medications throughout the process of the study were recorded.Results:At time T3 and T4, BRS decreased in Con group compared with T1 (P<0.05).In Dex group, compared with T1, BRS were significantly higher at T2 (P<0.05), decreased at T3 (P<0.05). Compared with T1, there were no significant difference in BRS at T4 (P>0.05). At time T2, T3 and T4, BRS in Dex group were higher than in Con group (P<0.05).Conclusions:The results indicate that arterial baroreflex function is significantly depressed during anaesthesia in healthy surgical patients. While dexmedetomidine improves the depressed baroreflex function throughout anaesthesia procedure.