Median Effective Concentration Of Ropivacaine For Pericapsular Nerve Group Block In Elderly Patients Undergoing Total Hip Arthroplasty

Objective:To discover the median effective concentration of ropivacaine of ultrasound-guided pericapsular nerve group block by sequential method in elderly patients undergoing hip arthroplasty.Method:Thirty-six patients with 20 males and 16 females,aged 60-80 yeas,BMI18-30 kg/m²,ASA physical statusⅠ～Ⅲ,prepared for total hip arthroplasty were selected to undergo pericapsular nerve group block with 20 ml ropivacaine.The concentration of ropivacaine for patients was started with 0.375%and the gap between each serial concentration was 1.2.Once the effect of prior block was positive,the concentration of the next patient would go down,or if negative,a higher concentration was provided to the following patient.The procedure was stopped until7 crossovers finished.Probability of regression was appointed to calculate the EC₅₀and the 95%confidence interval of ropivacaine.The NRS scores before block（T₀）and at 5 min（T₁）、10 min（T₂）、15 min（T₃）、20 min（T₄）after block and at 2 h（T₅）、6h（T₆）、12 h（T₇）、24 h（T₈）after operation were recorded.The complications of weakness of the quadriceps,local anesthetic intoxication,postoperative infection in puncturing area,nerve damage and hematoma were recorded.Results:The median effective concentration and 95%confidence interval of ropivacaine for pericapsular nerve group block was 0.185%and 95%confidence interval was 0.154%～0.213%.None of the patients occurred weakness of the quadriceps,local anesthetic intoxication,postoperative infection in puncturing area,nerve damage and hematoma.Conclusion:The EC₅₀ of ropivacaine using ultrasound-guided PENG block in elderly patients undergoing total hip arthroplasty is 0.185%and 95%confidence interval is 0.154%～0.213%.