Department of Anesthesia, Stanford University School of Medicine, Stanford, California 94305, USA.
Anesthesiology. 2011 Mar;114(3):529-35. doi: 10.1097/ALN.0b013e318209a92d.
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.
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 = 6 per group) coadministered with 200 μg morphine and 10 μg 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.
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).
Obese and nonobese patients undergoing cesarean delivery do not appear to respond differently to modest doses of intrathecal bupivacaine. This dose-response study suggests that doses of intrathecal bupivacaine less than 10 mg may not adequately ensure successful intraoperative anesthesia. Even when the initial block obtained with a low dose is satisfactory, it will not guarantee adequate anesthesia throughout surgery.
有研究表明病态肥胖产妇行椎管内麻醉时所需的局部麻醉药剂量可能较低。本研究旨在确定肥胖产妇行剖宫产术时蛛网膜下腔布比卡因的有效剂量（ED50/ED95）。
本研究为双盲研究，纳入择期行剖宫产术的病态肥胖产妇（BMI≥40）。42 名患者随机分为 6 组，每组 6 人，分别鞘内注射 5、6、7、8、9、10 或 11mg 重比重布比卡因，同时给予 200μg 吗啡和 10μg 芬太尼。成功（诱导）定义为针刺痛觉阻滞平面达到 T6 或以上，手术成功（操作）定义为成功（诱导）且手术全程无需硬膜外补充麻醉药。采用 logistic 回归模型确定 ED50/ED95 值。
手术成功（操作）的 ED50/ED95（95%置信区间）分别为 9.8（8.6-11.0）和 15.0（10.0-20.0），与先前采用相似方法确定的非肥胖人群的相应值相似。由于初始低剂量范围内阻滞失败的情况很少，我们无法测量阻滞成功（诱导）的 ED50/ED95 值。次要结局（即低血压、血管加压药使用、恶心和呕吐）无差异。
行剖宫产术的肥胖和非肥胖患者对小剂量蛛网膜下腔布比卡因的反应似乎没有差异。该剂量反应研究表明，小于 10mg 的鞘内布比卡因剂量可能无法充分确保术中麻醉成功。即使初始低剂量阻滞效果满意，也不能保证手术全程麻醉效果。
