Local anesthetic systemic toxicity
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) |
Diphenhydramine as Local Anesthetic
- Injectable 1% diphenhydramine (10 mg/mL) can be used as a local anesthestic alternative to ester/amide anesthetics[4]
- Sodium channel blocker mechanism
- 1-2 mL of 1% diphenhydramine at a time, to not exceed excessive sedation dose
- Typical vial is 50 mg/mL, so to make 10 mg/mL:
- 10 mL NS removed from 50 mL vial
- Add 10 mL of 50 mg/mL diphenhydramine to 40 mL of NS
- Sedation is dose related and is similar to what would be expected for IM doses
- Relative contraindications are the same for IM diphenhydramine administration
Clinical Features
Clinical course tends to be a dose-dependant progression from CNS symptoms to CVS symptoms and death[5]
- CNS symptoms
- Agitation
- Auditory changes/Tinnitus
- Metallic taste
- Slurred speech
- 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
- Methemoglobinemia - local anesthestics oxidize Fe2+ to Fe3+ in Hb
Sodium Channel Blockade Toxidrome
- Phenothiazines
- Antihistamines
- Sotalol
- TCAs
- Antipsychotics
- Cocaine
- Anti-spasmodics, cyclobenzaprine
- Chloroquine
- Anti-malarials
- Class Ia and Ic antiarrhythmics
- Local anesthetic systemic toxicity
- Venlafaxine 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[6]
- Hypercapnia, hypoxia, acidosis all worsen toxic effects[7]
- Manage seizures with benzodiazepines; propofol is an option but may worsen cardiovascular toxicity
- Temporary pacing may be required for symptomatic bradycardia
- Early activation of ECMO or consideration for transfer to ECMO center as cardiac arrest is often refractory to ACLS.
- 1 amp of sodium bicarbonate IV q2 min for:
- Vtach or VF
- Severe acidosis
- Lipid emulsion, (Intralipid) 20% solution[7]
- 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
- Maximum total dose 12 mL/kg.
- Consider drawing extra blood as will interfere with labs
- ACLS modifications:[8]
- 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.
- ↑ Sztajnkrycer MD. Local Anesthetics. In: Nelson LS, Howland M, Lewin NA, Smith SW, Goldfrank LR, Hoffman RS. eds. Goldfrank's Toxicologic Emergencies, 11e. McGraw-Hill; Accessed November 29, 2020. https://accessemergencymedicine.mhmedical.com/content.aspx?bookid=2569§ionid=210274249
- ↑ Scott DB. "Maximum recommended doses" of local anaesthetic drugs. Br J Anaesth. 1989 Oct;63(4):373-4. doi: 10.1093/bja/63.4.373. PMID: 2818914.
- ↑ Pavlidakey PG et al. Diphenhydramine as an Alternative Local Anesthetic Agent. J Clin Aesthet Dermatol. 2009 Oct; 2(10): 37–40.
- ↑ 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
- ↑ 7.0 7.1 Dillane D, Finucane BT. Local anesthetic systemic toxicity. Can J Anaesth. 2010 Apr;57(4):368-80.
- ↑ per ASRA (Am Soc of Regional Anesthesia)