Advancing the needle deeper than 2 cm during interscalene blockade increases the risk for which complication?

Advancing the needle deeper than 2 cm during an interscalene blockade is primarily associated with an increased risk of intrathecal injection. The interscalene block is typically performed to provide anesthesia or analgesia to the shoulder and arm by targeting the brachial plexus. The anatomical proximity of the cervical spine to the injection site means that if the needle is advanced too far, it may inadvertently enter the intrathecal space, leading to the administration of anesthetic agents directly into the cerebrospinal fluid. This can result in significant complications such as respiratory depression and other central nervous system effects, which are more serious than typical complications associated with injections outside of this space.

Interscalene block also carries risks for other complications, but advancing the needle beyond the recommended depth predominantly elevates the risk for intrathecal injection due to the anatomical considerations surrounding the cervical spine and the proximity to the intrathecal space. Understanding proper depth of needle insertion is critical in avoiding such serious unintended consequences during regional anesthesia techniques.