What is the treatment for a patient experiencing a lidocaine reaction?

Treatment of Lidocaine Reaction

Immediately discontinue lidocaine administration and initiate supportive care with 100% oxygen, continuous cardiac monitoring, and benzodiazepines for seizures, while having lipid emulsion 20% readily available for severe cardiovascular toxicity. 1, 2

Immediate Actions

Stop the lidocaine infusion immediately and preserve the pump with settings and memory intact for investigation. 1 Obtain blood samples in EDTA and lithium heparin tubes for later lidocaine level analysis. 1

Establish continuous monitoring including ECG, pulse oximetry, and blood pressure measurements every 5 minutes initially. 1 Administer 100% oxygen regardless of oxygen saturation. 1

Recognition of Toxicity Type

Lidocaine reactions are overwhelmingly systemic toxicity (dose-related) rather than true allergy, which represents only 1% of adverse reactions. 2 The clinical presentation follows a predictable concentration-dependent pattern:

Early CNS symptoms (appearing at 5-7 μg/mL plasma levels):

• Perioral tingling and numbness, tinnitus, light-headedness, dizziness 1, 2
• Nausea, drowsiness, confusion, slurred speech 3
• Muscle twitching and tremors 3, 1

Late CNS symptoms (appearing at >9 μg/mL):

• Seizures, altered consciousness, respiratory depression or arrest 3, 1

Cardiovascular symptoms (appearing later at >10 μg/mL):

• Bradycardia, sinus arrest, hypotension 3
• Wide-complex tachycardia (QRS ≥120 ms) 1
• Cardiovascular collapse and cardiac arrest 2

Seizure Management

Administer benzodiazepines as first-line therapy for seizures: lorazepam 1-2 mg IV or diazepam 5-10 mg IV. 1 This is critical because neurological symptoms appear at lower plasma concentrations than cardiovascular symptoms, making CNS signs the critical early warning system. 1

Cardiac Toxicity Management

For wide-complex tachycardia (QRS ≥120 ms), administer hypertonic sodium bicarbonate 1-2 mEq/kg (50-100 mEq) IV bolus. 1 Target arterial pH 7.45-7.55. 1 This intervention addresses the sodium channel blockade that characterizes severe lidocaine toxicity.

For cardiac arrest with pulseless electrical activity (PEA), administer a 100 mL bolus of 20% lipid emulsion immediately, followed by continuous infusion of 0.25 mL/kg/minute. 4 A case report demonstrated return of spontaneous circulation within 3 minutes of lipid administration in a patient with lidocaine-induced PEA arrest. 4 Lipid emulsion 20% should be readily available wherever IV lidocaine is used, and staff should know where it is kept. 3

Supportive Care Requirements

Maintain normal body temperature as hyperthermia worsens toxicity. 1 Check core temperature immediately if sympathomimetic response is present; initiate rapid external cooling if >38.5°C. 1

Monitor serum potassium as hypokalemia may develop during sodium bicarbonate therapy. 1

Obtain arterial blood gases every 2-4 hours to monitor pH, sodium, potassium, and ionized calcium. 1

Level of Care and Monitoring

Transfer to level 2 care (high dependency unit) with specific monitoring protocols:

• Observations every 15 minutes for the first hour 1
• Hourly observations minimum after the first hour 1
• Continuous ECG monitoring 1

This intensive monitoring is essential because lidocaine toxicity can develop in a delayed fashion up to 3.5 hours after administration, and plasma levels may continue to rise even after discontinuation, particularly with prolonged infusions. 5

True Anaphylaxis (Rare)

If true anaphylactic reaction is suspected (hypotension, bradycardia, urticaria, bronchospasm developing within 30 minutes), treat with:

• Intramuscular epinephrine immediately 6
• Fluid resuscitation 6, 7
• Antihistamines and corticosteroids 6
• Oxygen therapy 6

However, recognize that anaphylaxis to lidocaine is extremely rare, and most reactions presenting with hypotension and altered mental status represent systemic toxicity rather than allergy. 2, 6

Critical Pitfalls to Avoid

Do not delay treatment while waiting for plasma lidocaine levels, as delay in proper management may lead to acidosis, cardiac arrest, and death. 8 The correlation of plasma levels with symptoms is not linear, and systemic toxicity reflects unpredictable interactions between patient factors and drug pharmacokinetics. 3

Do not assume the absence of blood on aspiration guarantees avoidance of intravascular injection. 8 Toxicity can occur even with proper technique in high-risk patients (>70 years, heart failure, hepatic dysfunction, cardiogenic shock). 3, 2

Remember that toxicity is possible even with therapeutic doses in patients with hepatic cirrhosis, as oral and topical lidocaine undergoes extensive first-pass metabolism dependent on liver blood flow. 9