In the context of sedation, when is local anesthetic systemic toxicity a consideration, and what is the antidote?

• A. LAST may occur with inadvertent systemic absorption; treat with lipid emulsion therapy
• B. LAST is not a concern during sedation
• C. LAST is treated with naloxone
• D. LAST only occurs with intrathecal injections

Answer: (B)

The main idea is that local anesthetic systemic toxicity (LAST) is a real risk whenever local anesthetics enter the bloodstream in sufficient amounts, which can happen during sedation when blocks or local infiltration are performed or if there is an inadvertent intravascular injection. Early signs can be subtle, starting with perioral numbness or a metallic taste and progressing to dizziness, seizures, or cardiac symptoms if the toxicity worsens. The antidote is lipid emulsion therapy. Administering a 20% lipid emulsion provides a “lipid sink” that binds the lipophilic local anesthetic molecules, reducing their distribution to brain and heart and supporting cellular energy for the myocardium. A typical approach is a bolus dose of about 1.5 mL/kg, followed by an infusion of 0.25 mL/kg/min, with adjustments based on the clinical scenario and ongoing monitoring.

This matters in sedation because LAST is not confined to one route; it can occur with any local anesthetic use if systemic absorption is significant. It is not treated with naloxone, which targets opioid toxicity, and LAST is not limited to intrathecal injections—any administration route carries a risk if levels become toxic.