Determination of the ED_(50) of spinal anesthesia 0.75% ropivacaine for cesarean section / 中国临床药理学与治疗学

ABSTRACT

AIM: To determine the median effective dose(ED50) of spinal anesthesia 0.75% ropivacaine for cesarean section. METHODS: Thirty-two ASAⅠ-Ⅱ parturients undergoing elective cesarean section delivery with use of combined spinal-epidural anesthesia were enrolled in this study. The initial dose of was 12.8 mg of 0.75% ropivacaine, and the dosing intervals were 98.4% of the preceding dosage. Doses for subsequent parturients were determined by the response of the previous parturient. Successful anesthesia was defined as a loss of sensation to an acupuncture stimulus at the T7 level, full motor blockade within 10 minutes after administration of the local anesthetic, analgesia of incision and the satisfaction of skelaxin evaluated by one operator. ED50 and its 95% confidence interval (CI) was determined with use of Dixon method. RESULTS: Five parturients were rejected out the study because of doubtful anesthsia. According to the rest twenty-seven parturients' data, the ED50 of intrathecal 0.75% ropivacaine was 11.97 mg (95% confidence interval [CI], 11.75-12.19 mg). CONCLUSION: The ED50 of spinal 0.75% ropivacaine for cesarean delivery under the conditions of this study were 11.97 mg.