What is a hallmark sign of local anesthetic systemic toxicity (LAST)?

• A. CNS excitation or seizures
• B. Severe pain at the injection site
• C. Increased heart rate and blood pressure
• D. Nausea and vomiting

Answer: (A)

A hallmark sign of local anesthetic systemic toxicity (LAST) is CNS excitation or seizures. LAST occurs when local anesthetics enter the systemic circulation, leading to various central nervous system symptoms. Early signs often include feelings of lightheadedness, tinnitus, and perioral numbness, which can progress to more severe manifestations like seizures. These seizures result from the increased excitability of neurons and reflect a direct effect of the anesthetic on the central nervous system.

Recognizing CNS symptoms is critical because they often precede cardiovascular effects, which can include arrhythmias or cardiac arrest. Prompt identification and management of these symptoms are critical to preventing further complications.

The other options, while they may occur due to different causes or conditions, do not directly indicate the systemic toxicity of local anesthetics in the same definitive way as CNS excitation or seizures do. For instance, severe pain at the injection site could be an indication of multiple issues unrelated to systemic toxicity, such as vascular or nerve injury. Increased heart rate and blood pressure could be stress responses or relate to other medical conditions. Nausea and vomiting can arise from a multitude of factors, including anxiety or other non-specific side effects, but are less definitive indicators of LAST when compared to the direct and severe manifestations of