Undescribed Vascular Signatures: A Contraindication to Ultrasound-guided Parasagittal Infraclavicular Block! A Retrospective Observational Study

BACKGROUND: The ultrasound-infraclavicular block (US-ICB) is a popular and efficient block for below-elbow surgeries. However, the vascular anatomy of infraclavicular area close to the brachial plexus has remained unresearched. We aimed to explore the presence of aberrant vasculature in the infraclavicular area that could pose a contraindication to US-ICB. METHODS: In this retrospective observational study, we reviewed the US images of patients undergoing below-elbow surgery under US-ICB. Before performing the block, a scout scan of parasagittal infraclavicular areas was performed and the scan images were saved. The primary objective was to find the prevalence of aberrant vasculature due to which the US–ICB was abandoned. The secondary objective was to understand the pattern and position of the aberrant vessels. RESULTS: Out of 912 patients, 793 patients underwent surgery under US–ICB and in 119 patients (13.05%), the USG-ICB was abandoned due to aberrant vasculature close to the brachial cords and intended position of the needle tip. The anomalous vessels were identified in the lower inner, lower outer, and upper outer quadrants around the axillary artery (AA). Some of these vascular structures also had classical patterns which we described as “satellites,” “clamping,” or “hugging” of the AA. CONCLUSION: Anomalous vascular structures in the infraclavicular area were seen in 13.05% of patients planned for US–ICB. We, therefore, recommend, that a thorough scout US scan should be mandatorily performed ICB and in the presence of aberrant vascular structures, an alternative approach to brachial plexus block may be adopted.