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: https://doi.org/10.1503/cmaj.220835