Research Of CWT Method Of Time-frequency Analysis Of Heart Rate Variability For Real-time Assessment Of Autonomic Nervous Activity In Patients Undergoing Open Cholecystectomy

Objectives:Heart rate variability (HRV) refers to minor differences between cardiac cycle, which can offer a quantitative evaluation of the tenseness and the balance of the sympathetic and vagus nerve activities and their effect on cardiovascular motion. Gallbladder-cardiac reflex in cholecystectomy cause a certain impact on the cardiac autonomic nervous system and hemodynamics. In this study, we observed the changes of the hemodynamics, bispectral index (BIS) and HRV analysis indicators during general anesthesia in the patients who undergoing open cholecystectomy, in order to observe the abnormal reaction of the vagus nerve because of traction gallbladder, identify sensitive indicators and explore a new clinical monitoring method for the prevention of gallbladder-cardiac reflex and which caused serious circulation complications. Among the HRV analysis methods, continuous wavelet transform (CWT) analysis which can real-time monitor the cardiac autonomic nervous system activity was used mainly.Methods:Twenty-one patients scheduled for elective open cholecystectomy under general anesthesia were studied with mean age50.7±9.5years old and mean weight65±17kg, ASA Ⅰ～Ⅱ. Patients with cardiovascular disease, diabetes, mental and neurological disease were excluded. To avoid the impact of drugs on the basis ANS activity of patients, all patients were not given the drug before surgery. After entering the operation room, ECG, SpO2, BP were monitored, and the electrocardiosignal was collected continuously by home-built equipment. The signal was manipulated and calculated by Matlab software. Patients were induced by Midazolam0.05-0.1mg/kg, Sufentanil0.4μg/kg, Etomidate0.3mg/kg, Atracurium0.3-0.6mg/kg. Anesthesia was maintained by propofol target plasma concentration3-5μg/ml, Atracurium5-10μg-kg-1·min-1and Isoflurane. After tracheal intubation, the patients’breathing were maintained by mechanical ventilation, with tidal volume8-10mg/kg, frequency10-12times/min. The patients with spontaneous breathing were moved to anesthesia recovery room after surgery. In this study, there were five HRV sampling points:before induction (To), intubation (T1), intraoperative without traction gallbladder (T2), intraoperative traction gallbladder (T3), and before extubation (T4). We analyzed the signal of each period5min by the methods of time domain, frequency domain and nonlinear analysis. We analyzed the signal of30s when operating and stimulating during each period5min by the CWT analysis. HR, MAP and BIS were recorded at the same time of HRV.Result:(1)Hemodynamic parameters and BIS:Compared to To, HR and MAP increased at T1, the value of BIS decreased in other time points. Compared to T2, HR, MAP and BIS did not change significantly.(2)HRV analysis indicators:In contrast with To:the value of SDNN increased at T1, but decreased at T2, T3and T4; RMSSD decreased at Ti, T2and T4, but significant change was not observed at T3; the value of SD1decreased in other time points; SD2increased significantly at Ti, decreased at T2and did not change significantly at T3and T4. Compared to To, the values of TP and TPc increased at Ti, but decreased at T2, T3andT4. Compared to To, the values of LFn, LF/HF, LFcn and LFc/HFc increased at T1, T4and did not change significantly at T2; LFcn, LFc/HFc decreased significantly at T3, meanwhile LFn, LF/HF did not change significantly; the value of HF/LF did not change significantly in other time points. Compared to To, the values of HFn, HFcn and HFc/LFc decreased at Ti, T4and did not change significantly at T2; HFcn and HFc/LFc increased significantly at T3, meanwhile HFn did not change significantly. Compared to T2, the indicators of SD2, LFn, HFn, HF/LF, LFcn, HFcn, LFc/HFc and HFc/LFc showed statistic difference at T3, but LFcn, LFc/HFc, HFcn and HFc/LFc showed significant difference.(3)CorreIations:HRV indicators of time domain, frequency domain and nonlinear analysis are all short-time (5min) indicators. There were high correlation among the short-time HRV indicators reflecting the same subject, but low correlation between instantaneous indicators of CWT analysis and the short-time HRV indicators reflecting the same meaning as the CWT analysis indicators.Conclusion:During the monitoring of gallbladder-cardiac reflex in the open cholecystectomy, CWT analysis method monitored the HRV signal real-timely, reflected the real-time activity of ANS, showed the abnormal activity of the vagus nerve which the hemodynamic parameters, BIS and HRV indicators of time domains frequency domain and the nonlinear analysis did not express. Therefore, CWT analysis may be a new clinical monitoring tool to predict the gallbladder-cardiac reflex and which caused serious circulation complications.