文献学习|0.5%罗哌卡因用于超声引导下肋锁阻滞的中位有效容积

       产生有效的肋锁阻滞所需的罗哌卡因的中位有效剂量尚未确定。作者进行了这项剂量发现研究，目的是确定50%的患者成功实施肋锁阻滞手术麻醉所需的0.5%罗哌卡因的中位有效剂量(ED50)，以及95%的患者有效阻滞所需的计算剂量(ED95)。

      这项单臂前瞻性研究对象为40例ASAI-II，年龄18~60岁，体重指数18~30 kg/m2，计划在超声引导下进行肋锁阻滞下的前臂和手部手术。采用二元反应变量的样本升降序贯分配研究设计，确定0.5%罗哌卡因在肋锁间隙的用量。第一个病人接受了26毫升的0.5%罗哌卡因。麻醉成功或不成功后，下一位患者的局部麻醉量分别减少或增加2ml。感觉和运动阻滞评估每隔5min进行一次，持续30min，并采用3分量表进行评分。如果手术麻醉最低得分达到14分，并且外科医生能够在不需要补充麻醉的情况下继续手术，那么手术麻醉就被认为是成功的。

     局麻药用量为8~26ml，中心保序回归，经偏倚校正的Morris 95%CI自举得到ED50为13.5ml(95%CI，11.5~15.4ml)，ED95为18.9ml(95%CI，17.9~27.5ml)。

   19ml剂量的0.5%罗哌卡因有可能在超声引导下产生有效的肋锁阻滞，为95%的患者提供充分的手术麻醉。

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Background: The median effective dose of ropivacaine required for producing an effective costoclavicular block has not yet been determined. The authors conducted this dose-finding study with the objective of determining the median effective dose of 0.5% ropivacaine required to produce a successful costoclavicular block for surgical anesthesia in 50% of the patients (ED50) as well as the calculated dose required for effective blockadein 95% of the patients (ED95).

Methods: This single-armed prospective study was conducted on 40 American Society of Anesthesiologists physical status I or II patients, aged 18 to 60 yr, with a body mass index of 18 to 30 kg/m2, scheduled to undergo forearm and hand surgeries under ultrasound-guided costoclavicular block. A volume of 0.5% ropivacaine administered in the costoclavicular space was determined using the sample up-and-down sequential allocation study design of binary response variables. The first patient received a volume of 26 ml of 0.5% ropivacaine. After a successful or unsuccessful block, the volume of local anesthetic was decreased or increased, respectively, by 2 ml in the next patient. Evaluation of sensory and motor block was performed every 5 min for 30 min and graded using a 3-point scale. Surgical anesthesia was considered to be successful if a minimum score of 14 was achieved and the surgeon was able to proceed with surgery without needing to supplement anesthesia.

Results: The volume of local anesthetic administered ranged from 8 to 26 ml. Centeredisotonic regression with a bias-corrected Morris 95% CI derived by bootstrapping showed ED50 of 13.5 ml (95% CI, 11.5 to 15.4 ml) and ED95 of 18.9 ml (95% CI, 17.9 to 27.5 ml).

Conclusions: A 19-ml dose of 0.5% ropivacaine is likely to produce an effective ultrasound-guided costoclavicular block for providing adequate surgical anesthesia to 95% of the patients.