Study on ropivacaine epidural space additional minimum motor block concentration after spinal anesthesia

OBJECTIVE To determine ropivacaine concentration in application of lumbar epidural anesthesia for the elderly with urinary system surgery,to achieve full sensory-motor separation.METHODS Elderly people suffering from urinary tract diseases were given subarachnoid injection of 0.325% ropivacaine 3ml.At 40min,epidural administration was carried out according to sequential method,the initial concentration was 0.393% ropivacaine 15ml,concentration interval of 0.98.The probit regression calculated EC50 and its 95% confidence interval.RESULTS The EC50 for ropivacaine was 0.360%,95% CI 0.345% to 0.377%,the time of drug action was 50 ± 7min.CONCLUSION This study supports the use of 0.360% ropivacaine doses to ensure successful anesthesia.