Background: It has been suggested that morbidly obese parturients may require less local anesthetic for spinal anesthesia. The aim of this study was to determine the effective dose (ED 50 /ED 95 ) of intrathecal bupivacaine for cesarean delivery in morbidly obese patients. Methods: Morbidly obese parturients (body mass index equal to or more than 40) undergoing elective cesarean delivery were enrolled in this double-blinded study. Forty-two patients were randomly assigned to receive intrathecal hyperbaric bupivacaine in doses of 5, 6, 7, 8, 9, 10, or 11 mg (n ϭ 6 per group) coadministered with 200 g morphine and 10 g fentanyl. Success (induction) was defined as block height to pinprick equal to or more than T6 and success (operation) as success (induction) plus no requirement for epidural supplementation throughout surgery. The ED 50 /ED 95 values were determined using a logistic regression model. Results: ED 50 and ED 95 (with 95% confidence intervals) for success (operation) were 9.8 (8.6 -11.0) and 15.0 (10.0 -20.0), respectively, and were similar to corresponding values of a nonobese population determined previously using similar methodology. We were unable to measure ED 50 /ED 95 values for success (induction) because so few blocks failed initially, even at the low-dose range. There were no differences with regard to secondary outcomes (i.e., hypotension, vasopressor use, nausea, and vomiting). Conclusions: Obese and nonobese patients undergoing cesarean delivery do not appear to respond differently to mod-

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There is a weak association between clot strength (as assessed by kaolin-activated TEG®) and EBL in patients undergoing elective CD under neuraxial anesthesia, and a modest reduction in the degree of maternal hypercoagulability occurs in the early postpartum period after elective CD.