蛛网膜下腔注药速度对剖宫产脊麻感觉阻滞平面的影响

 目的 通过比较脊麻剖宫产手术蛛网膜下腔不同注药速度的布比卡因半数有效剂量(median effective dose,ED50)探讨注药速度对脊麻感觉阻滞平面的影响。方法 选择ASAⅠ～Ⅱ级拟在腰硬联合麻醉下行择期剖宫产的足月单胎妊娠产妇70例,电脑随机数字法分为快速注药组(F组,n=35)和慢速注药组(S组,n=35),F组与S组蛛网膜下腔分别以0.25和0.025 mL/s的速度注射0.5％等比重布比卡因。采用序贯法进行试验,每组第一例产妇的布比卡因剂量均为6.5 mg,剂量变化梯度为0.5 mg,感觉阻滞有效定义为局麻药注射完毕后15 min双侧无痛的阻滞平面达T6或以上。若上一例产妇有效,则下一例布比卡因的剂量降低0.5 mg,若上一例产妇无效,则下一例产妇布比卡因的剂量增加0.5 mg,采用Dixon Mood法计算两种注药速度时布比卡因ED50及其95％的可信区间(95％CI)。结果 F组布比卡因的ED50及其95％CI为6.17(6.03～6.32)mg,S组布比卡因的ED50及其95％CI为7.23(7.00～7.46)mg,F组布比卡因的ED50低于S组(P＜0.001)。结论 局麻药的推注速度是影响脊麻感觉阻滞平面的因素之一,在一定范围内,注药速度越快,剖宫产手术脊麻时达到相同阻滞平面所需的药物剂量越小。

Effect of intrathecal injection rate on sensory block level for cesarean section

Objective To investigate the effect of intrathecal injection speed of local anesthetic on sensory block level in parturients undergoing cesarean section by comparing the median effective dose(ED50) of bupivacaine at different injection speed. Methods Seventy parturients of ASA I or II,who had a normal singleton full term gestation pregnancy and scheduled for cesarean delivery were randomly allocated into two groups(n=35 in each):group F and S in which women received a intrathecal injection of 0.25 or 0.025 mL/s respectively.An up-down sequential allocation technique was used to determine the bupivacaine dose to each parturient with the first patient in each group receiving 6.5 mg 0.5% isobaric bupivacaine.Each time the bupivacaine dose increased or decreased 0.5 mg.Success was defined as a bilateral sensory block to T6 or higher after 15 min of the drug injection.When a success or a failure occurred,the subsequent patient′s dose of bupivacaine was respectively decreased or increased by 0.5 mg. Results Patient′s characteristics including age,height,weight and gestational weeks were similar in the two groups.The ED50 of intrathecal bupivacaine 6.17 mg(95%CI:6.03-6.32 mg) in group F was lower than 7.23 mg(95%CI:7.00-7.46 mg) in group S(P<0.001). Conclusions The intrathecal injection rate of local anesthetic is one factor of affecting sensory block level.In a certain range of injection rate,the faster the intrathecal injection speed,the lower dose will be required to achieve the same level of sensory block in cesarean delivery.