From the Guidelines
Local anesthetic systemic toxicity (LAST) during epidural placement can indeed lead to obtundation if sufficient local anesthetic enters the systemic circulation, and management should prioritize immediate discontinuation of local anesthetic, airway support, and administration of 20% lipid emulsion if necessary, as recommended by the 2023 American Heart Association guidelines 1. The presentation of LAST can vary, but it typically includes a range of neurological and cardiovascular symptoms. Initially, patients may experience perioral numbness, metallic taste, lightheadedness, tinnitus, visual disturbances, and agitation, which can progress to confusion, slurred speech, muscle twitching, seizures, and eventually loss of consciousness (obtundation) 1.
Key Symptoms and Management
- Neurological symptoms: perioral numbness, metallic taste, lightheadedness, tinnitus, visual disturbances, agitation, confusion, slurred speech, muscle twitching, seizures, and loss of consciousness
- Cardiovascular symptoms: hypertension and tachycardia initially, followed by hypotension, conduction blocks, bradycardia, ventricular arrhythmias, and potentially cardiac arrest
- Management: immediate discontinuation of local anesthetic, airway support, seizure suppression (with benzodiazepines if needed), cardiovascular support, and administration of 20% lipid emulsion (1.5 mL/kg bolus followed by 0.25 mL/kg/min infusion for 30-60 minutes) if cardiovascular compromise occurs, as recommended by the American Heart Association guidelines 1. The use of benzodiazepines to treat seizures associated with LAST is also recommended, with a Class I, Level of Evidence C-LD recommendation 1.
Prevention Strategies
- Careful aspiration before injection
- Use of test doses with epinephrine
- Incremental dosing
- Continuous monitoring during administration It is essential to note that the potency and toxicity of local anesthetics can vary, with bupivacaine being a more potent cardiotoxin than ropivacaine and lidocaine, and optimal treatments for bupivacaine poisoning may differ from other local anesthetics 1.
From the Research
Presentation of Local Anesthetic Systemic Toxicity
- Local anesthetic systemic toxicity (LAST) can present with various symptoms, including seizure, which is the most common presenting feature, occurring in 53% and 61% of cases reported in case reports and registries, respectively 2.
- Neurologic manifestations, such as obtundation, can occur due to the toxic effects of local anesthetics on the central nervous system 3.
- Cardiovascular manifestations, including cardiac arrest, can also occur due to the toxic effects of local anesthetics on the myocardium 4, 5.
Risk Factors for LAST
- Patients at extremes of age or with organ dysfunction are at higher risk of developing LAST 3.
- Inadvertent intra-arterial or intravenous injection, as well as repeated doses and higher doses of local anesthetics, are associated with a greater risk of developing LAST 3.
Treatment of LAST
- Early recognition and intervention, including supportive care and intravenous lipid emulsion 20%, are the mainstays of treatment for LAST 6, 4, 5, 3.
- Lipid emulsion therapy has been shown to be effective in reversing the cardiac and neurologic effects of local anesthetic toxicity 6, 4, 5.
- The use of epinephrine and vasopressin should be tailored to the specifics of an episode of LAST, and doses should be kept as low as possible while still achieving the desired effects 5.
Prevention of LAST
- Using ultrasound guidance, aspirating prior to injection, and utilizing the minimal local anesthetic dose needed are techniques that can reduce the risk of LAST 3.