What is the treatment for lidocaine toxicity?

Manifestations and Treatment of Lidocaine Toxicity

Clinical Manifestations

Lidocaine toxicity presents with neurological symptoms first, followed by cardiovascular manifestations at higher concentrations, with early recognition being critical for preventing progression to life-threatening complications. 1, 2

Neurological Manifestations (Earliest Signs)

• Peri-oral tingling and numbness - often the first warning sign 3
• Tinnitus (ringing in ears) 3
• Light-headedness and dizziness 3
• Restlessness, anxiety, and agitation 1
• Blurred vision 1
• Tremors 1
• Confusion and altered mental status 2
• Drowsiness or depression 1
• Seizures - occur at higher concentrations 2, 4
• Respiratory depression and arrest 1, 4
• Coma 4

Cardiovascular Manifestations (Late Signs)

• Wide-complex tachycardia (QRS prolongation) 3
• Bradycardia 5
• Prolonged Q-T interval 5
• Hypotension and cardiovascular collapse 4
• Cardiac arrhythmias 1, 6
• Cardiac arrest 1

Important caveat: Neurological symptoms appear at lower plasma concentrations than cardiovascular symptoms, making CNS signs the critical early warning system. 4 ECG changes are late manifestations and should not be relied upon as the primary monitoring tool. 3

Immediate Treatment Protocol

Step 1: Stop Administration and Assess

• Immediately discontinue lidocaine infusion 2, 4
• Preserve the pump with settings and memory intact for investigation 3
• Obtain blood samples in EDTA and lithium heparin tubes for later lidocaine level analysis 3
• Establish continuous cardiac monitoring (ECG, pulse oximetry, blood pressure every 5 minutes initially) 3, 7

Step 2: Airway and Breathing Management

• Ensure adequate oxygenation and ventilation 1
• Consider intubation for respiratory depression 8
• Administer 100% oxygen 3
• Prevent acidosis, as it worsens toxicity and can lead to cardiac arrest 1

Step 3: Seizure Management

• Administer benzodiazepines as first-line therapy for seizures 2, 9
  • Lorazepam 1-2 mg IV or
  • Diazepam 5-10 mg IV 9
• Avoid physical restraints without sedation, as this worsens sympathomimetic response 9

Step 4: Cardiac Toxicity Management

For wide-complex tachycardia (QRS ≥120 ms):

• Administer hypertonic sodium bicarbonate 1-2 mEq/kg (50-100 mEq) IV bolus 3, 8
• Target arterial pH 7.45-7.55 8
• Repeat boluses every 5-10 minutes until QRS narrows to <120 ms 9
• Monitor serum sodium (keep <150-155 mEq/L) and pH (keep <7.50-7.55) to avoid iatrogenic harm 8, 9

For refractory wide-complex tachycardia:

• Consider lidocaine 1-1.5 mg/kg IV as second-line therapy (paradoxically, lidocaine can treat cocaine-induced sodium channel blockade through competitive binding) 3, 8

Step 5: Lipid Emulsion Therapy (Critical Rescue Therapy)

Lipid emulsion 20% should be readily available wherever IV lidocaine is used and administered according to the Association of Anaesthetists' guideline for life-threatening toxicity. 3, 7, 10

• Indicated for cardiovascular collapse or refractory seizures 10
• Must be immediately accessible in all areas where lidocaine is administered 3
• Has demonstrated successful reversal of lipophilic drug toxicity 10

Step 6: Hypotension Management

• Administer IV fluid boluses (10 mL/kg) of normal saline 8
• Continue sodium bicarbonate therapy for persistent hypotension despite fluid resuscitation 8
• Consider venoarterial extracorporeal membrane oxygenation (VA-ECMO) for refractory shock unresponsive to high-dose vasopressors 8, 9

Step 7: Supportive Care

• Maintain normal body temperature (hyperthermia worsens toxicity) 8, 9
• Monitor serum potassium (hypokalemia may develop during sodium bicarbonate therapy) 8
• Check core temperature immediately if sympathomimetic response present; initiate rapid external cooling if >38.5°C 9

Critical Monitoring Requirements

During acute toxicity, patients require level 2 care (high dependency unit) with specific monitoring protocols: 3

• First hour: Observations every 15 minutes 3
• After first hour: Hourly observations minimum 3
• Continuous ECG monitoring 3
• Arterial blood gases every 2-4 hours (pH, sodium, potassium, ionized calcium) 9
• Nurses must be trained to recognize early neurological signs of toxicity 3

Important Clinical Pitfalls

Common errors that worsen outcomes:

• Delaying recognition because other explanations seem more likely - always consider lidocaine toxicity in any patient receiving the drug who develops neurological or cardiovascular symptoms 3
• Relying on ECG changes as primary monitoring - neurological symptoms precede cardiovascular manifestations 3, 4
• Giving additional sodium bicarbonate when sodium >150 mEq/L or pH >7.55 - causes iatrogenic harm 8, 9
• Mixing sodium bicarbonate with calcium-containing solutions or vasoactive amines in the same IV line - causes drug inactivation 9
• Using Class IA, IC, or III antiarrhythmics - these worsen cardiac toxicity 8
• Underestimating risk in elderly, debilitated, or hepatically impaired patients - these populations have decreased clearance and higher toxicity risk 1, 6

High-Risk Populations Requiring Extra Vigilance

• Elderly patients (>60 years) 6
• Patients with hepatic disease (decreased metabolism) 1
• Patients with cardiovascular disease 6
• Low body weight individuals 6
• Patients with acidosis (enhances ion trapping and toxicity) 5
• Infants and children (different pharmacokinetics) 4, 5

The correlation between plasma levels and toxicity is not linear, and toxic symptoms can persist even after lidocaine concentrations decrease below therapeutic levels. 4 This unpredictability mandates aggressive early intervention and prolonged monitoring even after apparent clinical improvement.