What are the symptoms of local anaesthetic (anesthetic) toxicity?

From the Guidelines

Local anesthetic toxicity presents with a spectrum of symptoms that progress from mild to severe as plasma concentrations increase, including perioral numbness, metallic taste, lightheadedness, tinnitus, visual disturbances, and slurred speech, and can lead to seizures, cardiovascular collapse, and cardiac arrest, as described in the 2015 American Heart Association guidelines update for cardiopulmonary resuscitation and emergency cardiovascular care 1. The symptoms of local anesthetic toxicity can be categorized into several stages, with initial symptoms often including:

• Perioral numbness
• Metallic taste
• Lightheadedness
• Tinnitus
• Visual disturbances
• Slurred speech As toxicity worsens, patients may experience:
• Muscle twitching
• Tremors
• Agitation
• Confusion
• Seizures Cardiovascular symptoms typically follow central nervous system effects and include:
• Hypertension and tachycardia initially
• Progressing to hypotension, bradycardia, conduction blocks, arrhythmias, and eventually cardiovascular collapse The progression of symptoms reflects how local anesthetics affect excitable membranes throughout the body, first blocking inhibitory pathways in the brain (causing excitation) before suppressing excitatory pathways (causing depression), as discussed in the 2015 guidelines update 1. Treatment involves stopping the anesthetic administration immediately, supporting airway and circulation, administering benzodiazepines for seizures, and in severe cases, lipid emulsion therapy (20% intralipid, 1.5 mL/kg bolus followed by 0.25 mL/kg/min infusion for 30-60 minutes) 1. Prevention through proper dosing, aspiration before injection, incremental administration, and having resuscitation equipment readily available, including 20% lipid emulsion, remains the best approach to managing this potentially life-threatening complication, as emphasized in the critical elements for the pediatric perioperative anesthesia environment 1.

From the Research

Symptoms of Local Anaesthetic Toxicity

The symptoms of local anaesthetic toxicity can be categorized into central nervous system and cardiovascular signs.

• Central nervous system signs include:
  • Excitation
  • Convulsions
  • Loss of consciousness
• Cardiovascular signs include:
  • Hypertension
  • Tachycardia
  • Premature ventricular contractions
  • Bradycardia
  • Conduction disturbances
  • Circulatory collapse
  • Asystole 2, 3, 4

Clinical Presentation

The clinical presentation of local anaesthetic systemic toxicity can be highly variable, with atypical presentations not uncommon 3.

• Initial symptoms are often characterized by central nervous system excitation, followed by inhibition 3
• Seizures and cardiac arrest are time-sensitive symptoms that require immediate treatment 5

Risk Factors

Certain patient populations are more vulnerable to local anaesthetic systemic toxicity, including:

• Infants
• Patients with decreased liver function
• Patients with low cardiac output 2

Prevention and Management

Prevention and management of local anaesthetic systemic toxicity involve careful choice and dosing of drugs, aspiration before injection, dose fractionation, use of intravascular markers, and ultrasound guidance 2, 3.

• Treatment of severe symptoms may include vasopressors, sodium bicarbonate, and intravenous lipid emulsion 4
• In cases of cardiac arrest, guidelines for advanced life support, including high-quality cardiopulmonary resuscitation and extracorporeal life support, should be followed 4