Influence Of Different Concentrations Of Ropivacaine On Respiratory Function Of Patients Following Ultrasound-guided Interscalene Plexus Block

Background:Ultrasound guided nerve block can not only improve the success rate of block,provide perfect postoperative analgesia,but also avoid or reduce the occurrence of complications,which makes low-dose local anesthetic nerve block possible.However,studies have found that even if the brachial plexus and its surrounding anatomical structure can be accurately identified under ultrasound,the incidence of phrenic paralysis caused by interscalene brachial plexus block is still as high as 58%-70%.At present,surrent studies at home and abroad mainly focus on the incidence of phrenic paralysis and how to reduce the incidence of phrenic paralysis.Some scholars believe that reducing the incidence of phrenic paralysis is mainly to reduce the volume and concentrations of local anesthetics.However,the duration of diaphragmatic paralysis and the recovery of respiratory function are not clear.Objective:To investigate the influence of different concentrations of ropivacaine on the recovery of respiratory function of patients following ultrasound-guided interscalene plexus block.Methods:Ninety adult patients undergoing elective shoulder arthroscopic surgery in Qingdao municipal hospital were selected.The ASA（American Society of Anesthesiologists）will be graded asⅠ-Ⅱ,ranging from 18 to 64 years old,gender is not limited,BMI（Body Mass Index）will be 18～26.9 kg/m².Patients were randomly divided into three groups according to the computer random number table method.Before induction of general anesthesia,the patients were randomly given 0.25%ropivacaine 20 ml（group A）,0.375%ropivacaine 20 ml（group B）and 0.5%ropivacaine 20 ml（Group C）for ultrasound-guided interscalene brachial plexus block,30 cases in each group.Preoperative visits were conducted by anesthesiologists for patients in each group to explain their conditions to the patients,and the patients signed the relevant informed consent after agreed to anesthesia and taught the patient to cooperate with the use of pulmonary function instrument.M-mode ultrasound and pulmonary function instrument were used to measure the preoperative（T₀）diaphragmatic activity and pulmonary function,and record the pulse oxygen saturation.All patients were anesthetized by the same experienced anesthesiologist.Brachial plexus block was performed in advance during anesthesia preparation.M-mode ultrasound and pulmonary function instrument were used to measure and record the diaphragm activity and pulmonary function at 30 min（T₁）after block completion,and pulse oxygen saturation was recorded.After entering the operating room,ECG monitoring was connected for general anesthesia.The general anesthesia scheme of the three groups was the same,2～2.5 mg/kg propofol and 0.15 mg/kg cisatracurium were used for anesthesia induction,double tube laryngeal mask was placed for mechanical ventilation,tidal volume was 6～8ml/kg,respiratory rate was 10～12 times/min,target controlled infusion of propofol（3～5μg/ml）,inhalation of sevoflurane for 1 MAC for anesthesia maintenance.Intraoperative P_ETCO₂was controlled between 35 to 45 mm Hg and BIS（bispectral index of EEG）value was controlled between 40 to 60 to ensure stable intraoperative vital signs and stable respiratory circulation.If intraoperative blood pressure increased 20 mm Hg or heart rate increased 10 times,Sufentanil 5μg can be used for regulation;ephedrine 5 mg was given when blood pressure decreased more than 20%;atropine 0.3 mg was given when heart rate was less than 50 times/minute,and each medication was recorded in detail.After the operation,the patient woke up,removal of laryngeal mask and sent to the anesthesia recovery room.After 30 minutes of observation,he was sent back to the ward when his vital signs were stable.M-mode ultrasound and pulmonary function instrument were used to measure and record the diaphragmatic activity and pulmonary function at 4 h（T₂）,6 h（T₃）,8 h（T₄）,10 h（T₅）and 12 h（T₆）after brachial block.The pulse oxygen saturation,sensory and motor function recovery were observed and recorded simultaneously.The pain VAS score,rescue analgesics and adverse reactions within 24 hours after awakening were recorded.All the measurement indexes of the above patients were implemented by the same anesthesiologist,and the anesthesiologist did not know the grouping situation of the patients.Results:1.Comparison of the diaphragmatic mobility between the three groups:compared with group A,the diaphragmatic mobility in calm breathing position was decreased at T_1-3and in deep breathing position was decreased at T_2-5in group B,showed statistically significant difference（P<0.05）,the diaphragmatic mobility in calm breathing position and deep breathing position were decreased at T_1-6in group C,showed statistically significant difference（P<0.01）.Compared with group B,the diaphragmatic mobility in calm breathing position was decreased at T_4-6and in deep breathing position was decreased at T_1-6in group C,showed statistically significant difference（P<0.05）.2.Comparison of the diaphragmatic paralysis rate between the three groups:compared with group A,the diaphragmatic paralysis rate in calm breathing position and deep breathing position was increased at T_2-3in group B,showed statistically significant difference（P<0.01）,the diaphragmatic paralysis rate in calm breathing position and deep breathing position were increased at T_1-4in group C,showed statistically significant difference（P<0.01）.Compared with group B,the diaphragmatic paralysis rate in calm breathing position was increased at T_2-4and in deep breathing position was increased at T_3-4in group C,showed statistically significant difference（P<0.05）.3.Comparison of the pulmonary function between the three groups:At T₁,FEV₁%（the proportion of FEV₁before block）and FVC%（the proportion of FVC before block）of group C were significantly lower than those of the other two groups,showed statistically significant difference（P<0.05）,and FVC%of group C was significantly lower than that of group A at T₂,showed statistically significant difference（P<0.05）.4.Comparison of the duration of sensory and motor block between the three groups:Compared with group A,the duration of sensory and motor block was prolonged in group B and group C,showed statistically significant difference（P<0.05）.5.There was no significant difference in pulse oxygen saturation,24 hours analgesia score,rescue analgesia and adverse reactions among the three groups（P>0.05）.Conclusion:For ultrasound-guided interscalene brachial plexus block,the incidence of diaphragmatic paralysis caused by low concentration of local anesthetics is lower and the recovery of respiratory function speed is faster at the same volume.