Evaluation Of The Effect Of Interscalene Brachial Plexus Block On Pulmonary Ventilation Based On Pulmonary Electrical Impedance Tomography

Background:interscalene brachial plexus block(ISB)is one of the classical approaches of brachial plexus block.It has provided effective pain relief during upper limb surgeries for many years,however,complications may still arise during and after the procedure.Unilateral diaphragmatic paralysis is a common complication after ISB.However,Patients with lung diseases may not tolerate the reduction in lung function that can result from unilateral diaphragmatic paralysis following ISB.Several studies have shown that decreasing the concentration of local anesthetics can reduce the occurrence of ventilation disorders.However,how to quickly and accurately judge the occurrence and degree of ventilation disorder under ISB that use different concentrations of local anesthetic has become a problem that catches more attention.Various technologies and equipment,such as ultrasound,pulmonary function testing,chest X-ray in standing position,phrenic nerve stimulator,and CT scan,can be used to evaluate the impact of interscalene brachial plexus block on lung ventilation.However,their perioperative use is limited due to certain constraints and considerations.Electrical impedance tomography(EIT)is a new technology.Electrical Impedance Tomography(EIT)is gaining popularity for perioperative use due to its non-invasive,real-time,convenient,and user-friendly ventilation monitoring features.Research has shown that EIT can effectively monitor lung ventilation after intercostal nerve block(ISB),providing a unique advantage in real-time ventilation monitoring.This study aims to use EIT for intuitive monitoring of lung ventilation function during interscalene brachial nerve block(ISB)with different concentrations of ropivacaine,in order to further clarify the impact of different concentrations of ropivacaine ISB on lung ventilation function.Methods: 90 patients undergoing elective upper limb surgery,18～60 years old,ASA grade I～II,BMI 18～28 kg/m2 were included.They were randomly divided into 0.25%ropivacaine group,0.33% ropivacaine group and 0.50% ropivacaine group.Brachial plexus block was performed via interscalene approach.The lung ventilation function was monitored by EIT,diaphragm movement measurement under ultrasound,forced vital capacity measurement of lung function,and the degree of motor block was evaluated by Bromage score.The main monitoring indicators were the EIT parameters(COV,DSS and NSS)before block(T0),10 minutes after block(T1),20 minutes after block(T2),and 30 minutes after block(T3).The secondary indicators were the ultrasonic diaphragm motion,FVC,Bromage score and VAS score at T0,T1,T2 and T3.Record the amount of opioids used 24 hours after operation and the time when the first VAS score increased by more than2.Results: 82 patients were included in the analysis.At T1,compared with 0.25% group,the COV of 0.33% group and 0.5% group was higher(P<0.05).At T1,T2 and T3,compared with 0.25% group,the NSS and DSS of 0.33% group and 0.5% group were larger(P<0.05),while there was no significant difference between 0.33% group and 0.5% group(P>0.05).Compared with T0,the COV,NSS and DSS of the three groups increased at T1,T2 and T3(P<0.05).At T1,T2 and T3,compared with 0.25% group,the diaphragm activity of the block side in 0.33% group and 0.50% group was smaller(P.At T1,compared with 0.25%group,the degree of motor block in 0.33% group and 0.50% group was higher(P<0.05),and there was no statistical difference between 0.33% group and 0.50% group(P>0.05).At T2 and T3,the degree of motor block in 0.50% group was higher than that in 0.25% group and 0.33% group(P.In terms of VAS score,there was no significant difference among the three groups at T0,T1,T2 and T3 time points.The occurrence time of the first VAS score greater than 2 in 0.25% group was shorter than that in the other two groups(P<0.05).There was no statistically significant difference in the amount of opiates used within 24 hours after operation.Conclusion: 0.25% ropivacaine has a slow onset and inadequate blocking effect for brachial plexus nerve block,but it has minimal impact on lung ventilation.In contrast,0.33% ropivacaine also has a slow onset and poor block effect for brachial plexus nerve block,but it significantly affects lung ventilation.On the other hand,0.50% ropivacaine has a rapid onset and good blocking effect for brachial plexus nerve block,but it significantly impacts lung ventilation.