[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anaesthesia and ICU](https://durgical.com/en/anaesthesia/) › [Regional anaesthesia](https://durgical.com/en/anaesthesia/areas/regional/) › Local anaesthetic systemic toxicity: the crisis

# Local anaesthetic systemic toxicity: the crisis

- Crisis

A dangerous reaction when too much numbing medicine reaches the blood, affecting the brain and heart; it can cause seizures and cardiac arrest.

Updated Nov 13, 2026

## Key points

- Suspect LAST with any neurological or cardiovascular change soon after a local anaesthetic injection.
- Under sedation or general anaesthesia, cardiovascular collapse may be the first and only sign.
- Give lipid emulsion early, per protocol, at the first sign of serious toxicity, not only after arrest.
- In arrest, use smaller-than-usual epinephrine doses and avoid vasopressin, calcium channel blockers, beta-blockers and other local anaesthetics.
- Bupivacaine is the most cardiotoxic; resuscitation may need to continue for a long time, and bypass or extracorporeal support may be needed.

On this page

- The basics Key points
- What it is
- How to recognise it
- Why it happens
- What to do at once
- How LAST usually progresses
- Costly mistakes
- Next step
- Memory aid
- Elsewhere in DurgiPedia

- Study Test yourself

- Connections Connections

## What it is

Local anaesthetic systemic toxicity (LAST) happens when the blood concentration of a local anaesthetic rises high enough to block sodium channels in the brain and heart. The usual causes are an accidental injection into a vessel, absorption from a very vascular site, or a total amount above the maximum safe dose by weight. It typically starts within minutes of injection but can appear later, especially with infusions and continuous catheters. Classically, neurological signs come first: perioral numbness, metallic taste, ringing in the ears, light-headedness, agitation or confusion, muscle twitching, then seizures and coma. Cardiovascular signs follow: early hypertension and tachycardia, then bradycardia, conduction block, wide complexes, ventricular arrhythmias, hypotension and cardiac arrest. In many cases the picture is atypical, and in sedated or anaesthetised patients cardiovascular collapse may be the first sign. Bupivacaine is the most cardiotoxic agent because it binds cardiac sodium channels strongly and leaves them slowly. Treatment follows a checklist: stop injecting, call for help, secure the airway with oxygen, treat seizures with a benzodiazepine, and give lipid emulsion early according to protocol. If cardiac arrest occurs, resuscitation is modified and often prolonged, because recovery is possible once the drug is redistributed.

## How to recognise it

- Early neurological symptoms: perioral numbness, metallic taste, tinnitus, light-headedness, dysarthria and agitation or drowsiness.
- Later neurological signs: muscle twitching, seizures, loss of consciousness and respiratory arrest.
- Cardiovascular signs: early hypertension and tachycardia, then bradycardia, widened QRS, ventricular arrhythmias, hypotension and asystole.
- Timing: usually within minutes of injection, but can be delayed with infusions, catheters or slow absorption.
- Patients at higher risk: extremes of age, heart disease, liver disease, low plasma proteins, acidosis and pregnancy.

## Why it happens

- Local anaesthetics block voltage-gated sodium channels; in the blood they reach the brain and heart, not just the target nerve.
- Inhibitory brain pathways are blocked first, causing excitation and seizures; at higher levels all neurons are depressed.
- In the heart, sodium-channel block slows conduction and causes arrhythmias; contractility also falls.
- Lipid emulsion is thought to act as a «lipid sink» that draws the drug out of tissues and also supports the heart's metabolism.
- Hypoxia, hypercarbia and acidosis increase the free drug and its toxicity, which is why the airway comes first.

## What to do at once

- Stop injecting the local anaesthetic at once — removes the source and limits the total amount in the blood.
- Call for help and fetch the LAST kit with lipid emulsion — the response needs several people and the drug must be at hand.
- Give oxygen and secure the airway, ventilating if needed — hypoxia and acidosis worsen toxicity.
- Treat seizures with a benzodiazepine — stops seizures that raise acidosis; avoid large amounts of propofol in a weak heart.
- Start lipid emulsion early, following the protocol — it binds the drug and helps the heart recover.
- In arrest, start CPR and use smaller-than-usual epinephrine doses — standard doses can worsen arrhythmias and lipid efficacy.
- Treat ventricular arrhythmias with amiodarone, not lidocaine or other sodium-channel blockers — adding them deepens toxicity.
- Continue resuscitation for a long time; ask early for bypass or extracorporeal support — recovery is possible as the drug clears.

## How LAST usually progresses

| Stage | Brain | Heart |
| --- | --- | --- |
| Early | Perioral numbness, metallic taste, tinnitus, light-headedness | Hypertension, tachycardia |
| Intermediate | Agitation, confusion, muscle twitching, seizures | Bradycardia, widened QRS, ventricular ectopy |
| Late | Coma, respiratory arrest | Ventricular tachycardia or fibrillation, hypotension, asystole |

## Costly mistakes

- Missing the early symptoms because the patient was not asked or was heavily sedated.
- Waiting for cardiac arrest before giving lipid emulsion.
- Using lidocaine for the arrhythmia, which adds more local anaesthetic.
- Giving standard epinephrine doses or vasopressin, which can worsen the outcome.
- Using propofol as a substitute for lipid emulsion: its lipid content is too small and it depresses the heart.
- Stopping resuscitation too early instead of continuing and seeking extracorporeal support.

## Next step

- Monitor the patient in a high-dependency or intensive care area for several hours, longer after cardiovascular instability, because toxicity can recur.
- Check for complications of lipid emulsion, such as pancreatitis, and warn the laboratory that lipid can interfere with blood tests.
- Involve a senior anaesthetist from the start and decide together whether to postpone surgery.
- Tell the patient, document the drug, site and timeline, and report the event to the local safety system.
- Prevent the next case: ultrasound guidance, lowest effective dose by weight, aspiration, incremental injection and monitoring during and after blocks.

## Memory aid

Stop, call, oxygen, seizure, lipid: stop injecting, call for help, oxygen and airway, benzodiazepine for the seizure, lipid emulsion early.

## Test yourself

Think of the answer, then tap the question to see it.

## What are the early neurological symptoms of local anaesthetic systemic toxicity?

Perioral numbness, metallic taste, tinnitus, light-headedness, slurred speech and agitation or drowsiness, before twitching and seizures.

## Why is bupivacaine more cardiotoxic than lidocaine?

It binds cardiac sodium channels strongly and dissociates from them slowly, so conduction block and ventricular arrhythmias persist.

## Which drugs are avoided when treating arrhythmias or arrest caused by LAST?

Vasopressin, calcium channel blockers, beta-blockers and other local anaesthetics such as lidocaine; epinephrine is used in smaller-than-usual doses.

## Why should the airway and ventilation come first in LAST?

Hypoxia, hypercarbia and acidosis increase free drug and its toxicity to the brain and heart, so oxygenation limits the harm.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anaesthesia/local-anaesthetic-systemic-toxicity-the-crisis/)

## Elsewhere in DurgiPedia

- [The nerve action potential](https://durgical.com/en/physiology/the-nerve-action-potential/)
- [The cardiac conduction system](https://durgical.com/en/physiology/the-cardiac-conduction-system/)
- [Local anaesthetic toxicity and methaemoglobinaemia](https://durgical.com/en/dentistry/local-anaesthetic-toxicity-and-methaemoglobinaemia/)
- [Seizure precautions and care during a seizure](https://durgical.com/en/nursing/seizure-precautions-and-care-during-a-seizure/)

## Connections

## Related 6

- [Peripheral nerve blocks in principle](https://durgical.com/en/anaesthesia/peripheral-nerve-blocks-in-principle/)
- [Epidural anaesthesia and analgesia](https://durgical.com/en/anaesthesia/epidural-anaesthesia-and-analgesia/)
- [Caudal block in children](https://durgical.com/en/anaesthesia/caudal-block-in-children/)
- [Advanced life support in hospital](https://durgical.com/en/anaesthesia/advanced-life-support-in-hospital/)
- [Standard intraoperative monitoring](https://durgical.com/en/anaesthesia/standard-intraoperative-monitoring/)
- [Labour analgesia](https://durgical.com/en/anaesthesia/labour-analgesia/)

## Related conditions 4

- [Local anaesthetic systemic toxicity (LAST)](https://durgical.com/en/conditions/local-anaesthetic-systemic-toxicity/)
- [Cardiac arrest (VF, pulseless VT, asystole, PEA)](https://durgical.com/en/conditions/cardiac-arrest/)
- [Status epilepticus](https://durgical.com/en/conditions/status-epilepticus/)
- [Ventricular tachycardia](https://durgical.com/en/conditions/ventricular-tachycardia/)

## In Pharmacology 8

- [Local anesthetics](https://durgical.com/en/pharmacology/classes/local-anesthetics/)
- [Bupivacaine](https://durgical.com/en/pharmacology/bupivacaine/)
- [Lidocaine](https://durgical.com/en/pharmacology/lidocaine/)
- [Ropivacaine](https://durgical.com/en/pharmacology/ropivacaine/)
- [Benzodiazepines](https://durgical.com/en/pharmacology/classes/benzodiazepines/)
- [Midazolam](https://durgical.com/en/pharmacology/midazolam/)
- [Epinephrine](https://durgical.com/en/pharmacology/epinephrine/)
- [Amiodarone](https://durgical.com/en/pharmacology/amiodarone/)

[← All of anaesthesia](https://durgical.com/en/anaesthesia/)

Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.

Sources: [Local Anesthetic Toxicity](https://www.ncbi.nlm.nih.gov/books/NBK499964/) (StatPearls (NCBI Bookshelf), 2026).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/anaesthesia/local-anaesthetic-systemic-toxicity-the-crisis/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anaesthesia/local-anaesthetic-systemic-toxicity-the-crisis/