Research Of Linear And Nonlinear Methods Of Heart Rate Variability For Assessment Of Automatic Nervous System During General Anesthesia

Objectives:Heart rate variability(HRV) refers to minor differences between cardiac cycle.HRV contains a lot of information about the cardiovascular regulation, while subtracting and analyzing of the information of HRV can offer a quantitative evaluation of the tenseness and the balance of the sympathetic and vagus nerve activities and their effect on cardiovascular motion.Along with the development of anesthesia,the analysis Of HRV has been the-focus of attention.Anesthesia drugs, procedures and surgical stimulations can significantly affect the functions of autonomic nerve system,followed by evident HRV changes.In recent years,the methods used for the analysis of HRV are mainly time-domain analysis and frequency-domain analysis.But the characteristics of HRV are nonlinear,while the nonlinear analysis is.seldom used.The purpose of this study is to explore the evaluation of cardiac ANS by using the linear and nonlinear analysis under the general anesthesia.Methods:Twenty-four patients scheduled for elective oral and maxillofacial surgery under general anesthesia were studied with mean age 43±5.4 years old and mean weight 56±6.1 kg,ASAⅠ～Ⅱ.Patients with cardiac.disease,diabetes, hypertension or psychoneurosis were excluded.All patients were given intramuscular injection with atropine 0.01 mg/kg,Midazolam0.05～0.1 mg/kg in 30 minutes before the operation.After entering the operation room,ECG,SpO₂,BP were monitored,and the electrocardiosignal was collected by home-built equipment mading by soundcard. The signal was manipulated and calculated by Matlab.Patients were induced by Midazolam 0.1mg/kg,Etomidate 0.3mg/kg,Fentanyl 3～5ug/kg.Anesthesia was maintained by propofol 50ug/kg·min,fentanyl 5ng/kg,vecuronicum 0.08mg/kg.The HRV signals were collected in 5 minutes at four time points,before induction(To), induction(T₁),operation(T₃ ) and analepsia(T₄).Both HR and MAP were recorded at the same time of HRV.Result:1,The hemodynamics features of patients:HR and MAP increased in response to tracheal intubation comparing to other time points. 2,The results of Time-domain analysis:In contrast with T₀,the value of SDNN decreased at T₂,but increased at T₁,T₃;And rMSSD and triangular index decreased at T₁,T₂,but increased at T₃ significantly.PNNso decreased at all time points after indication.3,The results of Frequency-analysis:The value of TP and VLF increased at T₁ and T₃,decreasing at T₂ in contrast with T₀;The values of HF and LF decreased at T₁ and T₂,but increased at T₃.Meanwhile the value of LF/HF increased at.T₁ and T₂,but decreased at T₃.4,The result of nonlinear analysis:The values of Complexity and Entropy decreased statistically,but recovered after analepsia.In the Lorenz plots analysis,the value of VAI decreased at T₁ and T₂,but the value of VLI increased significantly at T₁ and T₃,decreasing at T₂。The index of DFA increased at T₂,but no significant change was observed at other time points.5,There are different degrees of relevance among the various indicators of HRV, exactly,SDNN and TP,SDNN and VLI,SDNN and triangle index,VAI and rMSSD, HF and rMSSD,VAI and HF,VAI and PNN50,complexity and ApEn,scale index and ApEn,scale index and complexity.SDNN,TP,VLI,and triangle index can reflect the activity of autonomic nervous system;VAI,HF,rMSSD and PNN50 can reflect the vagus nerve on heart rate control in correlation analysis.Conclusion:The time-domain,frequency-domain and nonlinear analysis of HRV can reflect the activity of autonomic nervous system function in different degrees.The nonlinear analysis method is more sensitive than linear analysis.Individual differences are larger in frequency-domain analysis,and the data do not follow normal distribution,this phenomenon may be related to the analysis method.The nonlinear analysis can reflect the activity of autonomic nervous system function stably and sensitively.There are different degrees of relevance among the various indicators of HRV.