Which complication is the most common following supraclavicular nerve block?

The most common complication following a supraclavicular nerve block is Horner's syndrome. This syndrome results from the inadvertent involvement of sympathetic nerves during the block. When the sympathetic chain is affected, typically due to the proximity of the cervical sympathetic ganglion to the site of the block, it can lead to a triad of symptoms: ptosis (drooping of the eyelid), miosis (constricted pupil), and anhidrosis (lack of sweating) on the affected side of the face.

This complication, while concerning, is often transient and resolves on its own. It highlights the anatomical considerations and risks associated with performing a supraclavicular block, particularly the potential impact on surrounding structures, including the sympathetic nervous system.

The other options, while possible complications, are less common. Pneumothorax can occur due to improper needle placement but is not as frequently seen as Horner's syndrome. Vasovagal syncope can happen in any situation involving nerve blocks due to anxiety or response to pain, but again, it is not specific to the supraclavicular block. Local anesthetic toxicity is a serious concern, especially when large doses are used or when the anesthetic enters the vascular system, but it is typically less