Which anatomical areas may require consideration for the risk of local anesthetic systemic toxicity?

Local anesthetic systemic toxicity (LAST) is a serious condition that can arise when local anesthetics enter the systemic circulation, often leading to central nervous system and cardiovascular complications. The risk of LAST is closely tied to the vascularity of the area where the anesthetic is administered.

Areas with high vascularity, like the head and neck, are particularly prone to systemic toxicity. This high blood flow facilitates rapid absorption of the local anesthetic into the bloodstream, which can lead to increased systemic levels of the drug and a greater likelihood of toxicity. For instance, injections in the neck or a regional anesthetic technique in the head can quickly introduce the anesthetic into the circulatory system if the needle inadvertently enters a blood vessel or if the surrounding tissue absorbs the drug rapidly due to its vascular nature.

In contrast, areas with low vascularity, minimal nerve endings, or limited blood supply would typically present a lower risk for toxic systemic absorption. Consequently, when considering the risk for LAST, the anatomical areas characterized by high vascularity are the ones that warrant the most caution and monitoring.