Research Of Heart Rate Variability For The Effect Of Remifentanil On Autonomic Nervous Activity In Intubation Without Neuromuscular Blockade

Objectives:In many clinical conditions such as intraoperative neural monitoring during thyroid surgery and difficult airways,non-neuromuscular blocking tracheal intubation becomes an option during induction of general anesthesia in these patients.We used opioid drug remifentanil to suppress the stress response effectively caused by tracheal intubation without neuromuscular blockade.While observing general hemodynamic parameters and BIS monitoring,HRV analysis was used to reflect changes in the activity of the autonomic nervous system（ANS）.The present study on identify sensitive indicators of stress to adjust the use of anesthetic inducing drugs in the future and explore new clinical monitoring methods for non-neuromuscular blocking tracheal intubation.Methods:We chose 46 patients undergoing selective thyroidectomy under general anesthesia,ASA I^II;age 40⁶0 years old;height 156¹84cm;weight 49⁹0 kg;body surface area 1.67².1m²;BMI index 19.9³3.6;Mallampati Airway Ratings I^II.Exclusion criteria:Patients with difficult airways or suspected difficult airways,patients with preoperative arrhythmias and autonomic neuropathy.The preoperative medication was not applied to the patients.They were randomly divided into two groups（n=23）:remifentanil group（Group R）and cisatracurium group（Group C）.Patients were admitted to the room to monitor ECG,SpO₂,MAP,HR and BIS.Meanwhile,Prince 180D was adopted to collect the ECG signal and record the time points of each event.Matlab software was performed for signal processing and computational analysis.After the patient came to the operating room,we would mask oxygen for them,establish venous access,radial artery puncture to pressure measurement.After pumping dexmedetomidine for 15 min at speed of 0.8μg/kg/h,patients were injected midazolam 0.1mg/kg intravenously.Then Group R was injected remifentanil at dose of 2μg/kg intravenously,while the Group C used cisatracurium at dose of 0.1mg/kg and fentanyl 4μg/kg intravenously.After that,two groups were given intravenous injection of etomidate 0.4mg/kg with mask assisted ventilation,and then performed tracheal intubation and mechanical ventilation.The present study included 4 sampling points:basic state（T₀）,induction（T₁）,intubation（T₂）,and 5 minutes after intubation（T₃）.The four point signals were selected for time domain,frequency domain and non-linear analysis.The corresponding HR,MAP,and BIS monitoring for each time period were recorded synchronously,and all results were statistically analyzed.Results:（1）HR:At T₂ and T₃,compared with Group C,Group R was significantly lower（P<0.05）.MAP and BIS:Compared with T₀,the two group were significantly lower at T₁,T₂,and T₃（P<0.05）.（2）HRV analysis indicators:The changes of SDNN,logTP,LF/HF,and SD2 in the two groups were basically the same:Compared with T₀,the two groups were significantly higher at T₁ and T₂（P<0.05）,and there was no significant difference at T₃（P>0.05）.Compared with T₁,the two group at T₂ and Group R at T₃ were significantly lower（P<0.05）.Compared with T₂,the two group significantly decreased at T₃（P<0.05）.The changes of RMSSD and SD1 in the two groups at each time point were basically the same:Compared with T₀,the two groups decreased at T₁,T₂,and T₃.At T₁,the Group R decreased compared to the Group C.At T₂ and T₃,the Group R was elevated compared with the Group C.Conclusions:In this study,remifentanil at dose of 2μg/kg for anesthesia induction without neuromuscular blocking tracheal intubation can completely meet the clinical conditions of tracheal intubation,sympathetic nerve activity was significantly inhibited,the stress response during intubation is significantly smaller than that of the control group.