Minimum effective local anesthetic dose of intrathecal ropivacaine for arthroscopic meniscectomy / 重庆医学

ABSTRACT

Objective To determine the minimum effective local anesthetic dose (ED50 ) of spinal ropivacaine for arthroscopic meniscecto-my .Methods Twenty-five patients undergoing arthroscopic meniscectomy under combined spinal-epidural anesthesia received intrathecal ropivacaine .ED50 of ropivacaine was determined by the sequence method .The effective criteria were as followsthe level of sensory block reaching at least T12 within 20 min after injection of the local anesthetic ;the motion block reaching the Bromage Scale score ≥2 within 20 min after injection of the local anesthetic ;no supplemental epidural anesthetic at least 1 h after injection of the local anesthetic .The initial dose was 15mg and according to the effective or ineffective results in previous patient ,a dose of ropivacaine 1 mg was decreased or increased . Results ED50 of ropivacaine for the arthroscopic meniscectomy was 12 .24 mg(95% CI 12 .09-12 .39) .Conclusion The dose of ropiva-caine more than 12 .24 mg for arthroscopic meniscectomy is the best .But the anesthetic effect may be related with the specific gravity of the local anesthetic and the patients′factors(height ,weight ,age) .