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  • The Review Course in Family Medicine

LAST but not Least: A quick guide for Local Anesthetic Systemic Toxicity

1. How Common is LAST?

Local Anesthetic Systemic Toxicity (LAST) occurs in 1 out of every 1000 administrations.

The main culprits are extremity nerve blocks, naso-orophayngeal infiltration and


2. Recognize the Symptoms

Early signs of toxicity include dizziness, oral numbness, or metallic taste within the first 5

minutes of administration. Severe manifestations of seizures, arrythmias and cardiac

arrest may occur up to 6hrs after initial symptom onset.

3. What About High Risk Groups?

Use the minimal effective dose often 10 - 20% dose reduction in high-risk groups like the

elderly, pregnancy and those with renal and cardiac disease.

4. Preventing LAST

Using epinephrine and slow push (<1ml/s) under US guidance reduces chances for

systemic toxicity. Always know the maximum recommended dose of the anesthetic you

want to use.

5. Managing Complications

Manage severe complications by first managing the ABCs. Lipid emulsions (bolus

followed by infusion) can also be used to absorb systemic anesthetic.


Local anesthetic systemic toxicity

Ryan Antel and Pablo Ingelmo

CMAJ September 26, 2022 194 (37) E1288; DOI:



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