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Local anesthetic systemic toxicity
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Contents
Background
- Acronym: LAST
- Life-threatening adverse reaction to local anesthetic toxicity.
- Incidence = ~0.2% of nerve blocks
- Generally occurs within minutes of injection
Causes[1]
- Injection of local anesthetic into systemic circulation
- Exceeding the maximum dose of local anesthetic (see table below)
- Absorption of anesthetic into systemic circulation by injection into extremely vascular area.
Maximum Doses of Anesthetic Agents
| Agent | Without Epinephrine | With Epinephrine | Duration | Notes |
| Lidocaine | 5 mg/kg (max 300mg) | 7 mg/kg (max 500mg) | 30-90 min |
|
| Mepivicaine | 7 mg/kg | 8 mg/kg | ||
| Bupivicaine | 2.5 mg/kg (max 175mg) | 3 mg/kg (max 225mg) | 6-8 hr |
|
| Ropivacaine | 3 mg/kg | |||
| Prilocaine | 6 mg/kg | |||
| Tetracaine | 1 mg/kg | 1.5 mg/kg | 3hrs (10hrs with epi) | |
| Procaine | 7 mg/kg | 10 mg/kg | 30min (90min with epi) |
Clinical Features
Clinical course tends to be a dose-dependant progression from CNS symptoms to CVS symptoms and death[2]
- CNS symptoms
- Agitation
- Auditory changes
- Metallic taste
- Seizures or drowsiness
- Coma
- Respiratory arrest
- Cardiovascular[1]
- Early signs
- Tachycardia
- Ventricular dysrhythmia
- Hypertension
- Late signs
- Bradycardia
- Conduction block
- Cardiovascular collapse
- Asystole
- Early signs
Differential Diagnosis
- Anaphylaxis
- Anxiety
Sodium Channel Blockade Toxidrome
- Phenothiazines
- Antihistamines
- Sotalol
- TCAs
- Antipsychotics
- Cocaine
- Anti-spasmodics, cyclobenzaprine
- Chloroquine
- Anti-malarials
- Class Ib antiarrhythmics
- Local anesthetic systemic toxicity
Evaluation
- Clinical diagnosis
Workup
- Directed by clinical picture
- Blood levels of anesthetic are available, but not clinically useful.
Management
- Aggressive supportive care (including airway management) and application of ACLS
- Ventilate with 100% FiO2 - bolus dose of 50-100mg IV succinylcholine paralyzes without depressing CNS or CV[3]
- Hypercapnia, hypoxia, acidosis all worsen toxic effects[4]
- Manage seizures with benzodiazepines; propofol is an option but may worsen cardiovascular toxicity
- Lipid emulsion, (Intralipid) 20% solution[4]
- Lipid sink, binds to local anesthetic
- 1.5 mL/kg bolus over 1 minute
- Then, 0.25 mL/kg/min for 20 min or until hemodynamic stability achieved
- ↑ to 0.5 mL/kg/min if hemodynamic status declines
- ACLS modifications per ASRA (Am Soc of Regional Anesthesia):
- Avoid vasopressin
- Avoid calcium-channel blockers and beta-blockers
- Amiodarone preferred in ventricular dysrhythmias
Disposition
- Admit
See Also
External Links
References
- ↑ 1.0 1.1 Fencl JL. Local anesthetic systemic toxicity: perioperative implications. AORN J. 2015 Jun;101(6):697-700.
- ↑ Kamel I, Trehan G, Barnette R. Intralipid Therapy for Inadvertent Peripheral Nervous System Blockade Resulting from Local Anesthetic Overdose. Case Reports in Anesthesiology. 2015;2015:486543. doi:10.1155/2015/486543.
- ↑ GlobalRPH. Management of Local Anesthetic Emergencies. http://www.globalrph.com/local-anesthetics.htm
- ↑ 4.0 4.1 Dillane D, Finucane BT. Local anesthetic systemic toxicity. Can J Anaesth. 2010 Apr;57(4):368-80.
