Effect Of Ultrasound-guided Supraclavicular Brachial Plexus Block On Electromyography Of The Diaphragm And Pulmonary Function

Objectives To investigate the effect of two volumes of the same concentration ropivacaine on diaphragm compound muscle action potentials?CMAPs??phrenic nerve conduction time?PNCT?and pulmonary function before and after SCBPB under Ultrasound-guided.Methods 1?Eighty patients scheduled for internal fixation removal of hardware for internal fixation after healing of an upper limb fracture distal to the shoulder were consecutively enrolled into the study and randomly assigned 1:1 to Group A,which received 20 ml 0.375% ropivacaine,and Group B,which received 30 ml 0.375% ropivacaine,40 cases in each group.2?Patients were fasted for 8 hours before anesthesia.In the preparation room,routine electrocardiography?ECG?,pulse oximetry?Sp O2?while without oxygen,and noninvasive blood pressure?NBP?monitoring were applied.3?Spirometry was performed as the patients in the seated position.The forced vital capacity?FVC?,the percentage of FVC,and forced expiratory flow in the first second?FEV₁?were measured and recorded before SCBPB,The test was repeated three times for each patient.The means from three acceptable tests were calculated.4?Patients were examined with the head rotated 30 degrees in the contralateral direction in a supine position.Nerve conduction monitor?Cascade,Cadwell industries,America?was used to collect PNCT and CMAP.The amplitude of the diaphragm CMAP was measured from the negative peak to the positive peak of the waveform in micro volts??V?.The latency of the diaphragm CMAP,expressed as phrenic nerve conduction time?PNCT?,was measured from stimulation to diaphragm CMAP onset in milliseconds?ms?.The mean amplitude and latency of three tests were calculated.5?All the patients completed SCBPB under Ultrasound-guided in the anesthesia preparation room,measured and recorded pulmonary function?FVC?FVC%?FEV₁??PNCT and amplitude of CMAP 30 min after block in the same way,the means from three acceptable tests were calculated.The time to onset and duration of sensory and motor block,the anesthetic effect in the operation,changes in blood oxygen saturation and complications especially respiratory complication were evaluated 30 min after block.6?Statistical analysis Statistical analyses were performed using IBM SPSS Statistics,version 22.Measurement data of normal distribution are reported as mean ± standard deviation?SD?,Non-normal distribution data are presented as medians and interquartile range?IQR?.Enumeration data were compared with ?2 test.Patients' general data using single factor analysis of variance.Between-group differences in amplitude and latency?PNCT?of diaphragm CMAP were analyzed with analysis of covariance.Between-group differences in pulmonary function test results were analyzed using the Wilcoxon rank sum test.P<0.05 was considered statistically significant.Results 1 ? There was no statistical differences in demographic and clinical characteristics between the two groups?P>0.05?.2?The mean time to onset of sensory block and the duration of sensory or motor block did not differ between groups?P>0.05?.The mean time to onset of motor block was significantly longer in Group A than in Group B?P<0.05?.3?The amplitude of CMAP in the two groups were decreased 30 min after block when compared to baseline.The mean amplitude of the diaphragm CMAP was significantly lower in Group B than in Group A?P<0.05?.The PNCT in the two groups were prolonged 30 min after block.There was no difference in mean PNCT between the two groups?P>0.05?.4?Pulmonary function was decreased in all patients 30 min after SCBPB compared to baseline.The changes in FVC?Group A,-8.1% vs.Group B,-16.5%?,FVC%?Group A,-8.0% vs.Group B,-17.1%?,and FEV₁?Group A,-9.5% vs.Group B,-15.2%?from pre-to post-SCBPB were significantly less in Group A than in Group B?P < 0.05?.5?One patient was converted to general anesthesia because of block failure in Group A.Six patients?18%?in Group A versus three patients?9%?in Group B required 25–50 ?g fentanyl.Transient dyspnea and oxygen desaturation developed in two patients in Group B.No significant changes in blood pressure or heart rate were observed in either group.There were no significant differences in the incidence rates of fentanyl supplementation,dyspnea,and oxygen desaturation between groups.Conclusion this study demonstrates that a satisfied and similar anesthetic effect is achieved by 20 ml and 30 ml 0.375% ropivacaine for ultrasound-guided SCPBP.However,the degree of phrenic nerve palsy and diaphragm potentials was less reduced and lung function was less impaired in patients who received 20 ml vs 30 ml 0.375% ropivacaine.