What are the uses of lidocaine in emergency medicine?

Lidocaine Uses in Emergency Medicine

Lidocaine serves three primary roles in emergency medicine: as an antiarrhythmic for shock-refractory ventricular fibrillation/pulseless ventricular tachycardia, as an analgesic adjunct for acute pain management, and as a local anesthetic for procedures. 1, 2

Cardiac Arrest and Ventricular Arrhythmias

Shock-Refractory VF/pVT in Adults

• Either amiodarone or lidocaine may be used for ventricular fibrillation or pulseless ventricular tachycardia that persists after CPR, defibrillation, and vasopressor therapy (Class IIb recommendation). 1
• Administer lidocaine 1-1.5 mg/kg IV as initial dose for ventricular tachycardia. 3
• Maintenance infusion: 2-4 mg/min continuous IV. 3
• Critical caveat: No antiarrhythmic drug, including lidocaine, has been shown to improve survival to hospital discharge or neurologic outcomes—the benefit is limited to short-term return of spontaneous circulation. 1
• Establishing vascular access for lidocaine should never delay defibrillation or compromise CPR quality, as these interventions actually improve long-term survival. 1

Shock-Refractory VF/pVT in Pediatrics

• The American Heart Association reaffirms that either lidocaine or amiodarone may be used for pediatric shock-refractory VF/pVT, with one study showing lidocaine improved return of spontaneous circulation compared to amiodarone, though survival to discharge was equivalent. 1
• Pediatric dosing differs from adults and requires weight-based calculation. 1

Post-Resuscitation Prophylaxis

• Initiation or continuation of lidocaine may be considered immediately after return of spontaneous circulation from VF/pVT cardiac arrest (Class IIb, weak evidence). 1
• One observational study showed prophylactic lidocaine reduced recurrent VF/pVT arrest by 66% (OR 0.34), though survival benefit disappeared in propensity-matched analysis. 4
• The evidence is insufficient to recommend routine use, but there is no clear evidence of harm when used in this context. 1, 4

Contraindications for Antiarrhythmic Use

• Never use lidocaine for wide complex tachycardia due to accessory pathways (e.g., Wolff-Parkinson-White syndrome with atrial fibrillation/flutter)—it has no effect on supraventricular arrhythmias and can be dangerous. 3
• Prophylactic lidocaine is not recommended for suspected acute coronary syndrome or myocardial infarction, as early studies showed association with increased mortality, possibly from asystole and bradyarrhythmias. 1

Acute Pain Management

Systemic Analgesia

• Intravenous lidocaine provides analgesic, antihyperalgesic, and anti-inflammatory effects for acute pain conditions in the emergency department. 2
• Effective for visceral/central pain, renal colic, and various neuropathic pain conditions. 2
• The analgesic mechanisms are multifaceted beyond simple sodium channel blockade, allowing safe administration via different routes. 2

Procedural Anesthesia

• Lidocaine serves as the local anesthetic of choice for emergency procedures requiring infiltration or topical anesthesia. 2
• Maximum infiltrative dose without epinephrine: 1.5-2.0 mg/kg in children; 3.0-4.5 mg/kg with epinephrine. 5
• Topical 4% liposomal lidocaine (LMX4) provides anesthesia in approximately 30 minutes for IV placement, venipuncture, lumbar puncture, abscess drainage, and joint aspiration. 5

Critical Dose Adjustments and Safety

High-Risk Populations Requiring Dose Reduction

• Reduce maintenance infusion rate in severe hepatic dysfunction—lidocaine is metabolized almost exclusively by the liver, and half-life can exceed 20 hours in cardiogenic shock versus 1-2 hours normally. 3
• Reduce dose in patients older than 70 years due to increased toxicity risk. 3
• In infants under 6 months, reduce all amide local anesthetic doses by 30%. 3, 5
• Maximum infusion rate: no more than 120 mg/hour regardless of patient size. 1
• Use ideal body weight for dose calculation: (height in cm - 100) for men; (height in cm - 105) for women. 1

Timing Restrictions with Regional Anesthesia

• Do not start IV lidocaine within 4 hours of any nerve block, fascial plane block, or infiltration of laparoscopic port sites to avoid cumulative local anesthetic toxicity. 1
• Avoid combining multiple lidocaine-containing products simultaneously. 5

Toxicity Recognition and Management

• Early CNS symptoms: perioral numbness, facial tingling, metallic taste, tinnitus, lightheadedness, slurred speech, muscle twitching. 3, 5
• Progressive CNS toxicity: drowsiness, loss of consciousness, seizures, coma, respiratory arrest. 3, 6
• Cardiovascular toxicity: bradycardia, sinus arrest, hypotension, myocardial depression, ventricular arrest. 3
• Treat seizures promptly with benzodiazepines and discontinue lidocaine immediately. 6
• After 12-24 hours of continuous infusion, reduce dose by 1 mg/min as half-life increases after 24-48 hours. 3

Practical Implementation Considerations

Institutional Requirements

• IV lidocaine use for acute pain should be ratified by local hospital medication governance committees with a standard operating procedure covering dosing, monitoring, adverse effect recognition, and toxicity treatment. 1
• Administration should be initiated only by or on advice of a consultant experienced with IV lidocaine infusions. 1
• Obtain explicit informed consent when possible, explaining limited clinical benefit in most patients and potential risks including euphoria, facial flushing, and toxicity symptoms. 1

Monitoring Requirements

• Continuous ECG monitoring for heart rate, AV conduction abnormalities, and QT prolongation is mandatory during antiarrhythmic use. 7
• Do not use in patients weighing less than 40 kg for systemic infusions. 1