What is a common clinical sign of systemic toxicity from local anesthetics?

The presence of a metallic taste and tinnitus is a notable clinical sign associated with systemic toxicity from local anesthetics. This occurs because local anesthetics, particularly when they enter systemic circulation, can affect the central nervous system, leading to various neurological manifestations. The metallic taste is often one of the earliest symptoms reported by patients experiencing systemic effects, and tinnitus arises due to the drug's influence on auditory pathways.

These symptoms serve as warnings that toxicity may be developing, necessitating immediate attention and potentially modification of the anesthetic technique being utilized. Understanding these clinical signs is crucial for practitioners, as early recognition can help prevent severe complications associated with local anesthetic overdose, such as seizures or cardiovascular collapse.