Ultrasound Evaluation of the Sacral Area and Comparison of Sacral Interspinous and Hiatal Approach for Caudal Block in Children

Background: Although caudal block via the sacral hiatus is a common regional technique in children, it is sometimes difficult to identify the hiatus. A needle approach via the S2-3 interspace can be used as an alternative to the conventional approach. The authors compared the feasibility and clinical characteristics between the S2-3 approach and hiatal approach, in addition to ultrasound study. Methods: Sacral space depth, dural sac end level, and caudal space depth were evaluated using ultrasound with high-frequency linear probe in the lateral decubitus position in 317 anesthetized children (study 1). in another 162 children who underwent ambulatory urological surgeries, success rate, drug spread, and clinical characteristics were compared between the hiatal and S2-3 approaches (study 2). Results: The dural sac end level was S2U (S3M-L5M). The median depth of the sacral space at the S2-3 level was 7.3 mm, whereas the caudal space depth at the hiatus was 2.9 mm. The overall success rate was 96.3% in both groups. The success rates at the first puncture attempt were 96.2% in the S2-3 group and 77.5% in the hiatus group. Drug spread level and clinical characteristics were similar between the two groups. Conclusions: The S2-3 approach can be applied as a useful fallback method to the conventional landmark approach In children, especially in those older than 36 months who present with difficult identification of the sacral hiatus.