Correlation Between Preoperative Heart Rate Variability And Hypotension Of Subarachnoid Block In Elderly Patients Undergoing Orthopedic Surgery

BackgroundLower limb orthopedic surgery is one of the most common operations in elderly patients over 60 years old.Subarachnoid block is an effective and safe analgesic method that can provide effective and safe analgesia in lower limb orthopedic surgery.It is currently a widely used clinical anesthesia method.One,compared with general anesthesia,subarachnoid block has the advantages of providing good intraoperative and postoperative analgesia,rapid recovery,and high patient satisfaction.However,subarachnoid block also has many complications.Among them,hypotension and bradycardia are the most common adverse reactions.Due to sympathetic nerve damage and arterial elasticity reduction in elderly patients,when subarachnoid block is received Low blood pressure is more likely to occur.Subarachnoid block lags the sympathetic nerves to be blocked,the activity is weakened,and the parasympathetic nerve activity is increased,resulting in a decrease in systemic vascular resistance,peripheral resistance vasodilation and a decrease in return blood volume,resulting in a decrease in cardiac output.In the early stage of hypotension,when the body is in the compensatory phase,routine monitoring such as heart rate and blood pressure cannot provide important information for the anesthesiologist’s reference,and cannot predict the occurrence of hypotension and promptly intervene in patients.Heart rate variability is a non-invasive,simple and dynamic monitoring index that can be operated at the bedside and can reflect the functional status of the human autonomic nervous system.Studies have shown that the basic value of heart rate variability before anesthesia has a certain correlation with hypotension after anesthesia.Therefore,the main purpose of this study is to explore whether there is a correlation between preoperative heart rate variability and subarachnoid hypotension in elderly patients with lower limb orthopedic surgery.MethodsThis study included 150 elderly patients who planned to undergo subarachnoid block surgery for lower limb orthopedics in Zhujiang Hospital of Southern Medical University from 2020.06 to 2021.01.Among them,32 were males and 118 were females,aged 60-90 years old,ASA classification Ⅰ-Ⅲ.All patients had 24-hour dynamic electrocardiograms collected the day before the operation.After the patient enters the operating room,the peripheral venous access is opened,and the radial artery puncture is performed under lidocaine local anesthesia to measure the pressure.Before anesthesia,5-7ml/kg is used to supplement the diet loss,and after anesthesia,the speed is 6-8ml/kg/h.Enter the crystal liquid.The patient was intravenously administered midazolam 0.03-0.04 mg/kg before intraspinal anesthesia.The patient took the left knee position,underwent subarachnoid puncture in the L3-4 space,and slowly injected 3ml of ropivacaine hydrochloride with a concentration of 0.5%through the subarachnoid needle into the subarachnoid of the patient’s head.Patients with hysteresis in spinal canal were transferred to the supine position and acupuncture was used to evaluate the patient’s subarachnoid sensory block.Record blood pressure,heart rate,pulse oxygen saturation,and sensory block level every 1 min for the first 10 minutes,and then record blood pressure,heart rate,and pulse oxygen saturation every 2.5 minutes until the subarachnoid block lags 30 minutes,and record the sensory block level until Reach the highest sensory block level.Record the occurrence of hypotension and the use of vasoactive drugs.ResultsThere were no statistically significant differences in gender,age,height,weight,BMI,history of hypertension,history of diabetes,baseline blood pressure,baseline heart rate,0.5%ropivacaine volume,level of sensory block,infusion volume,type of operation,ASA grade between the hypotensive group and the non-hypotensive group.the heart rate variability analysis index SDANN of the two groups of patients,P<0.05,the difference was statistically significant;the heart rate variability analysis index of the two groups of patients SDNN,SDNNI,rMSSD,NN50,pNN50,SDSD,TP,HF,LF,LF/HF,VLF,ULF and other differences were not statistically significant.The analysis of the correlation between the heart rate variability index SDANN and the occurrence of hypotension,P<0.05,the difference was statistically significant;the analysis of the correlation between the rest of the heart rate variability analysis index and the occurrence of hypotension,P>0.05,the difference was not statistically significant.ConclusionsThe preoperative heart rate variability analysis index SDANN in elderly patients with lower limb orthopedic surgery has a certain correlation with the occurrence of subarachnoid hypotension,and has a certain correlation with the severity of hypotension.