What are the presenting symptoms of Local Anesthetic Systemic Toxicity (LAST) at the time of epidural administration?

From the Guidelines

Local anesthetic systemic toxicity (LAST) during epidural placement typically presents with central nervous system symptoms, including perioral numbness, metallic taste, lightheadedness, tinnitus, and agitation, before advancing to cardiovascular complications, as reported in the 2023 American Heart Association focused update 1. The presentation of LAST can vary depending on the specific local anesthetic used, with more lipid-soluble agents like bupivacaine causing more severe cardiac toxicity.

• Early signs of LAST include:
  • Perioral numbness
  • Metallic taste
  • Lightheadedness
  • Tinnitus
  • Agitation
• As toxicity worsens, patients may develop:
  • Slurred speech
  • Confusion
  • Muscle twitching
  • Seizures
• Cardiovascular symptoms follow, including:
  • Hypertension and tachycardia initially
  • Progressing to hypotension, bradycardia, arrhythmias, and potentially cardiac arrest The management of LAST includes immediate cessation of local anesthetic administration, airway management, seizure control with benzodiazepines if needed, and cardiovascular support, as recommended in the 2023 American Heart Association guidelines update 1. The definitive treatment for severe LAST is 20% lipid emulsion therapy, with a recommended dose of 1.5 mL/kg bolus followed by 0.25 mL/kg/min infusion for 30-60 minutes, as supported by the 2023 American Heart Association focused update 1 and the 2015 American Heart Association guidelines update 1.

From the Research

Presentation of Local Anesthetic Systemic Toxicity

• Initial symptoms of local anesthetic systemic toxicity are characterized by central nervous system signs such as excitation, convulsions, followed by loss of consciousness and respiratory arrest 2
• These symptoms are often accompanied with cardiovascular signs such as hypertension, tachycardia and premature ventricular contractions 2
• Further increase of plasma concentration of local anesthetic induces bradycardia, conduction disturbances, circulatory collapse and asystole 2
• Seizures are the most common presentation of local anesthetic systemic toxicity, occurring in 53% and 61% of cases reported in case reports and registries, respectively 3

Risk Factors

• Infants, patients with decreased liver function and low cardiac output are vulnerable to systemic toxicity 2
• Patients at extremes of age or with organ dysfunction are at higher risk of developing local anesthetic systemic toxicity 4
• Inadvertent intra-arterial or intravenous injection, as well as repeated doses and higher doses of local anesthetics are associated with greater risk of developing local anesthetic systemic toxicity 4

Prevention and Management

• Guideline-directed monitoring, securing a venous line, preparation of medication to treat convulsions and lipid emulsions are required when performing regional anesthesia 2
• Small-dose, divided administration, using agents with low toxicity such as ropivacaine and levobupivacaine, performing an aspiration test are recommended for prevention of local anesthetic systemic toxicity 2
• If systemic toxicity is suspected, halt administration of local anesthetic, request assistance, secure venous line, airway, administration of 100% oxygen and if necessary tracheal intubation and artificial respiration should be immediately performed 2
• Benzodiazepines are recommended to treat convulsions, and administration of 20% lipid emulsion according to the protocol is recommended to treat severe hypotension and arrhythmia 2, 5, 6