Local anesthetic toxicity can manifest with a progression of symptoms that vary from mild to severe, depending on the plasma concentration of the anesthetic. Early signs of toxicity often include circumoral numbness, a metallic taste, tinnitus, light-headedness, and visual disturbances. As the condition progresses, patients may experience restlessness, anxiety, disorientation, and involuntary muscle twitches, typically starting in the face or distal limbs. Severe central nervous system effects can lead to seizures.
Cardiovascular symptoms also emerge with increasing toxicity levels, presenting as hypotension, either bradycardia or tachycardia, and potentially dangerous ventricular arrhythmias. Bupivacaine, in particular, is notorious for its cardiovascular effects, which can culminate in cardiac arrest. Management of local anesthetic systemic toxicity (LAST) includes immediate cessation of local anesthetic administration, securing the airway, ensuring adequate oxygenation, and providing cardiovascular support with intravenous fluids and vasopressors. Seizures are typically managed with benzodiazepines, and in severe cases, Intravenous Lipid Emulsion Therapy is administered. This therapy is especially effective against toxicity from highly lipid-soluble anesthetics like bupivacaine. Prompt recognition and treatment of these symptoms are crucial to reduce the risk of serious outcomes.
In cases of toxicity, a 20% lipid emulsion (intralipid) treatment is recommended, starting with a 1-2 ml/kg bolus followed by a 0.25 ml/kg/min infusion for 30-60 minutes, with possible repeat boluses every 3-5 minutes up to a maximum of 4 ml/kg. Sodium bicarbonate (1-2 mEq/kg) may be administered if sodium channel blockade is suspected to be contributing to cardiac toxicity. Seizures or seizure prophylaxis can be treated with Versed (0.2 mg/kg IM, or 0.02-0.1 mg/kg IV).
| Intervention | Detail |
|---|---|
| Stop the local anesthetic | Immediate cessation of administration |
| Airway and oxygenation | Secure the airway and ensure adequate oxygenation |
| Cardiovascular support | Intravenous fluids and vasopressors |
| Seizures | Benzodiazepines — Versed 0.2 mg/kg IM, or 0.02–0.1 mg/kg IV |
| Lipid emulsion, initial | 20% intralipid 1–2 mL/kg bolus, then 0.25 mL/kg/min infusion for 30–60 minutes |
| Lipid emulsion, repeat | Repeat boluses every 3–5 minutes, to a maximum of 4 mL/kg |
| Sodium bicarbonate | 1–2 mEq/kg if sodium channel blockade is suspected of contributing to cardiac toxicity |
