| Background and ObjectiveThe risk of induction period was greater during general anesthesia. Perfect induction of general anesthesia required stable hemodynamics and tried to produce as little stress reaction as possible. Sevoflurane is a new type inhalation anesthetics with many advantages such as rapid induction, quick recovery, fine controllability on depth of anesthesia, gentle depression on circulation, low irritation on air-way, analgesia and muscle relaxation in some degress and so on. Now sevoflurane has been used widely in clinical anesthesia, is easily accepted by patients with good controllability on anesthesia maintenance. Although the sevoflurane has many advantages, but its analgesia and muscle relaxation is weak. If you want to achieve satisfactory analgesia and muscle loose effect, require a higher sevoflurane concentration with bigger hemodynamic effects. To reduce side effects of various anesthetic drugs and the stress response during perioperation, require other auxiliary anesthetic drugs in narcotic induction and maintenance.Dexmedetomidine is a potent and highly selective [alpha] 2-adrenoceptor agonist, it provides dose-dependent sedation, analgesia, anxiolysis, sympatholysis, stable hemodynamic, and reduces requirements for opioids and anesthetic agents, and has little respiratory depression. Dexmedetomidine make sevoflurane induced process more smoothly and also can reduce restless degree after sevoflurane anesthesia. Besides short half-life make dexmedetomidine has extensive clinical application value.But there was few of the study that inhalation of sevoflurane to induction and maintain general anesthesia in adults with dexmedetomidine on sevoflurane MAC value and the stress reaction during induction. Therefore, the purpose of this study was to evaluate the effects of dexmedetomidine on bispectral index (BIS) and stress reaction undergoing trachea cannula under anesthetic induction with sevoflurane, and determine the effects of dexmedetomidine on the mininluln alveolar concentration (MAC) of sevoflurane.Materials and Methods74 ASA physical statusⅠandⅡadults, age 18 to 55 years, weighing 40-80kg, undergoing elective surgery with at least a 10 centimeter skin incision. All patients were randomly divided into three groups, C group (0.9% NaCl solution control group, n=25); D1 group (loading dose of 0.5μg/kg dexmedetomidine, then pumping the dose of 0.3μg/kg/h dexmedetomidine continuous with intravenous pump, n=25); D2 group (loading dose of 1.0μg/kg dexmedetomidine, then pumping the dose of 0.5μg/kg/h dexmedetomidine continuous with intravenous pump, n=24).When three groups patients got into the operating room, some Indexes such as electrocardiogram (ECG), mean arterial pressure (MAP), heart rate (HR) and bispectral index (BIS) were monitored. Patients were given a dexmedetomidine or 0.9% NaCl solution infusion for at least 15 minutes before anesthetic induction with sevoflurane in oxygen by face mask, Scoline 1.0mg/kg and Remifentanil 1μg/kg by intravenous injection.After tracheal intubation, a target sevoflurane concentration was commenced at a target determined by the response of the previous patient in the group (Dixon up-and-down method) and maintained for 15 minutes while the dexmedetomidine or 0.9% NaCl solution continued to run. When patients got in the operating room(To), HR, MAP, BIS and OAA/S were recorded at 1 minutes and 5 minutes after loading does of dexmedetomidine, before and 5 minutes after tracheal intubation, before and 5 minutes after surgical incision. Those venous blood samples were collected in heparinized tubes just before and 5 minutes after loading does of dexmedetomidine, before and 5 minutes after tracheal intubation. Those blood samples were used to analysis cortisol concentrations.Enumeration data adopts a chi-square test.All measurement data were expressed as mean±S.E.M. For statistical comparison between data sets, we used repeated measures analyse variance (ReANOVA) for repeated measure variable, One-Way ANOVA for completely random design data, Kryskal-Wallis tests for abnormal distribution and heterogeneity of variance. Sevoflurane MAC values were determined using the "Dixon up and down" method. Significance was established at P<0.05.ResultsDemographic data of the patients in three groups were comparable.In group D1 and group D2, HR,BIS and Cor decreased compared with basic value respectively after dexmedetomidine loading dose was given (P<0.05).After tracheal intubation, in group C, MAP, HR, Cor and BIS values increased significantly (P<0.01); in group D1 and group D2, MAP and HR increased (P<0.05),however, the change in BIS values was not statistically significant (P>0.05);Cor increased in group D1 but decreased in group D2 (P<0.05).MAP, HR, Cor and BIS values were significantly lower in group D1 and group D2 than group C after tracheal intubation (P<0.05). The MAC of sevoflurane was 1.87% in 0.9% NaCl solution group,1.70% in the loading does of 0.5μg/kg dexmedetomidine group, and 1.48% in the loading does of 1.0μg/kg dexmedetomidine group. Dexmedetomidine 1.0μg/kg decreased the MAC of sevoflurane by 20.9%, whereas there was no difference between the group C and the group D1.Conclusion1,Dexmedetomidine significantly decreased cortisol concentrations and stress reaction to tracheal intubation during sevoflurane anesthesia induction.2,Loading dose of 1.0μg/kg dexmedetomidine (maintenance dose of 0.5μg/kg/h dexmedetomidine) with intravenous injection, decreased the MAC of sevoflurane by 20.9%. |
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