Lumbar Neuraxial Ultrasound for Spinal and Epidural Anesthesia: A Systematic Review and Meta-Analysis

Background This systematic review examines the evidence for preprocedural neuraxial ultrasound as an adjunct to lumbar spinal and epidural anesthesia in adults. Methods We searched MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials databases from inception to June 30, 2014, for randomized controlled trials (RCTs) and cohort studies that reported data answering one or more of the following 3 questions: (1) Does ultraound accurately identify a given lumbar intervertebral space? (2) Does ultrasound accurately predict the needle insertion depth required to reach the epidural or intrathecal space? (3) Does ultrasound improve the efficacy and safety of spinal or lumbar epidural anesthesia? Results Thirty-one clinical trials and 1 meta-analysis were included in this review. Data from 8 studies indicate that neuraxial ultrasound can identify a given lumbar intervertebral space more accurately than by landmark palpation alone. Thirteen studies reported an excellent correlation between ultrasound-measured depth and needle insertion depth to the epidural or intrathecal space. The mean difference between the 2 measurements was within 3 mm in most studies. Thirteen RCTs, 5 cohort studies, and 1 meta-analysis reported data on efficacy and safety outcomes. Results consistently showed that ultrasound resulted in increased success and ease of performance. Ultrasound seemed to reduce the risk of traumatic procedures but there was otherwise insufficient evidence to conclude if it significantly improves safety. Conclusions There is significant evidence supporting the role of neuraxial ultrasound in improving the precision and efficacy of neuraxial anesthetic techniques. What's New We know that neuraxial ultrasound is a useful complement to clinical examination when performing lumbar central neuraxial blocks. It provides anatomical information including the depth of the epidural space, the identity of a given intervertebral level, and the location of the midline and interspinous/interlaminar spaces. This information can be used to successfully guide subsequent needle insertion. Since 2010, new data from RCTs and 1 meta-analysis suggest that neuraxial ultrasound increases the success and reduces the technical difficulty of lumbar central neuraxial blocks. Findings from the meta-analysis suggest that neuraxial ultrasound reduces the risk of traumatic procedures, and thus may possibly contribute to the safety of lumbar central neuraxial blocks.