Evaluation Of The Effect Of Dexmetomidine On Vagal Nerve Activity During General Anesthesia By Heart Rate Variability

Objective: To choose general anesthesia patients underwent selective operation in maxillofacial surgery,it makes the observation of intravenous infusion of dexmedetomidine(DEX)before induction,to evaluate the effect of DEX on autonomic nervous function in operation by analysis methods in heart rate variability(HRV),especially the changes in activity of vagus nerve.Methods: To select 50 intravenous and inhalation combined general patients with elective operation in maxillofacial surgery,whose situations meet the requirements of ASA I-II,Age 18-65,Body weight 52-85 Kg,exclusion of abnormal heart rate,hypertension,diabetes and autonomic nervous function.All patients were not given premedication.After entering the operation room with sober cooperation,patients received the connection of multifunction ECG monitoring and the establishment of venous channels.Before induction,the two groups were constant speed pump injected with 1?g/kg DEX(group D)or the same amount of 0.9%Na Cl(group C)for 10 min,routine intravenous anesthesia induction after finish pumping.Methods in induction of anesthesia: successive intravenous injection with midazolam 0.05mg/kg,fentanyl 2?g/kg,etomidate 0.3mg/kg and vecuronium 0.05mg/kg,meanwhile,closed mask pressurized oxygen inhalation for nitrogen removal 5min.Transnasal special-shaped tracheal tube intubation under the photopic vision of laryngoscope,and then it makes the controlled mechanical ventilation via GE9100 anesthesia machine.1% Propofol as anesthesia maintenance medication is targeted controlled infused by TCI infusion system.Effect-site concentration is set to 2?g/ml,each interval 1 hours plus vecuronium 0.05mg/kg and fentanyl 1 ?g/kg.BIS maintained at 40~60 during the operation and the dosage of propofol was adjusted according to the BIS value.Sodium lactate ringer's injection 8ml·kg-1·h-1 maintains fluid in operation.Preoperative local anesthesia is given to the surgical site.After patients resumed spontaneous breathing,all kinds of protective reflexes were recovered and conscious,the airway secretions were removed and the tracheal catheter was removed and sent back to PACU.Postoperative patients routinely receive monitoring.At the same time,the whole course electrocardiogram was collected.Three 5min periods were intercepted from the continuous RR interval time sequence of the whole course: preoperative(T0),intubation(T1),and intraoperative(T2).The ECG data of the 3 time periods were analyzed in time domain,frequency domain,PRSA techno Logy and nonlinear HRV respectively,and the heart rate(HR),mean arterial pressure(MAP)and BIS value of 3 time periods were recorded synchronously.Results:(1)Hemodynamic parameters and BIS value: At T1,T2,MAP,HR and BIS in D group were significantly lower than that of group C(P<0.05).In group D,compared with T0,MAP and HR increased significantly in T1(P<0.05),BIS value decreased significantly(P<0.05).MAP,HR,and BIS value decreased significantly in T2(P<0.05).Compared with T1,the MAP and HR decreased significantly at T2(P<0.05),and the BIS value increased significantly(P<0.05).In group C,compared with T0,MAP and HR increased significantly at T1(P<0.05),and BIS value decreased significantly(P<0.05).At T2,the value of MAP and BIS decreased significantly(P<0.05);compared with the time point of T1,MAP and HR decreased significantly at T2(P<0.05).(2)HRV analysis index: Compared with group C,at T1,SDNN,SD2,log HF,log LF,LFn,LH/HF in D group significantly reduced(P<0.05)while HFn increased(P<0.05).In T2,LFn,LF/HF in D group decreased significantly(P<0.05)and RMSSD,SD1,log HF and HFn significantly increased(P<0.05).Compared with T0,SDNN,SD2,LFn,LF/HF and log TP increased significantly at T1 in both groups(P < 0.05),RMSSD,SD1,log HF,HFn and DC decreased significantly in both groups(P < 0.05),and log LF decreased significantly in group D(P < 0.05),but LF/HF was no significant difference(P > 0.05)in group C at T2,but HFn significantly increased in both groups(P < 0.05).The other HRV indexes in both groups were significantly decreased(P < 0.05).Compared with T1,HFn increased significantly in both groups(P < 0.05),and SDNN,SD2,log LF,LFn,LF/HF,log TP decreased significantly(P < 0.05),RMSSD,SD1,log HF decreased significantly in group C(P < 0.05).Conclusion: Preoperative administration of DEX can increase significantly the activity of vagus nerve during the course of general anesthesia.