方法：通过检索Central、CINAHL、EMBASE、Global Health、MEDLINE、Scopus和Web of Science等文献数据库，检索从建库最初到2020年2月13日的随机对照试验，纳入以传统体表标志触诊为对照、术前超声检查为干预措施的行椎管内镇痛麻醉的产妇。对于连续和二分结果，我们分别使用逆方差法计算平均差值，使用Mantel-Haenszel方法计算风险比。
原始文献来源：B. Young, D. Onwochei and N. Desai. Conventional landmark palpation vs. Preprocedural ultrasound for neuraxial analgesia and anaesthesia in obstetrics–a systematic review and meta-analysis with trial sequential analyses.[J].Anaesthesia, 2020 Sep 27: doi:10.1111/anae.15255.
Conventional landmark palpation vs. Preprocedural ultrasound for neuraxial analgesia and anaesthesia in obstetrics–a systematic review and meta-analysis with trial sequential analyses
The aim of this systematic review and meta-analysis was to examine the efficacy, time taken and the safety of neuraxial blockade performed for obstetric patients with the assistance of preprocedural ultrasound, in comparison with the landmark palpation method. The bibliographic databases Central, CINAHL, EMBASE, Global Health, MEDLINE, Scopus and Web of Science were searched from inception to 13 February 2020 for randomised controlled trials that included pregnant women having neuraxial procedures with preprocedural ultrasound as the intervention and conventional landmark palpation as the comparator. For continuous and dichotomous outcomes, respectively, we calculated the mean difference using the inverse-variance method and the risk ratio with the Mantel–Haenszel method. In all, 22 trials with 2462 patients were included. Confirmed by trial sequential analysis, preprocedural ultrasound increased thefirst-pass success rate by a risk ratio (95%CI) of 1.46 (1.16–1.82), p = 0.001 in 13 trials with 1253 patients. No evidence of a difference was found in the total time taken between preprocedural ultrasound and landmark palpation, with a mean difference (95%CI) of 50.1 (-13.7 to 113.94) s, p = 0.12 in eight trials with 709 patients. The quality of evidence was graded as low and very low, respectively, for these co-primary outcomes. Sub-group analysis underlined the increased benefit of preprocedural ultrasound for those in whom the neuraxial procedure was predicted to be difficult. Complications, including postpartum back pain and headache, were decreased with preprocedural ultrasound. The adoption of preprocedural ultrasound for neuraxial procedures in obstetrics is recommended and, in the opinion of the authors, should be considered as a standard of care, in view of its potential to increase efficacy and reduce complications without significant prolongation of the total time required.