Can chest pain in a patient taking lidocaine (local anesthetic) be attributed to the medication and what is the appropriate workup?

Chest Pain in a Patient Taking Lidocaine: Potential Causation and Appropriate Workup

Chest pain in a patient taking lidocaine could be due to lidocaine toxicity and requires immediate evaluation for both cardiac causes and lidocaine-related adverse effects.

Lidocaine as a Potential Cause of Chest Pain

Lidocaine can cause cardiovascular adverse effects that may present as chest pain through several mechanisms:

1. Direct cardiac effects: Lidocaine at toxic levels can cause:

   • Myocardial depression 1
   • Cardiac arrhythmias 1, 2
   • Hypotension that may lead to cardiac ischemia 2

2. Dose-dependent toxicity: As plasma lidocaine concentrations increase, cardiovascular symptoms become more prominent:

   • At moderate levels: cardiac arrhythmias may occur 1
   • At higher levels: myocardial depression and potentially ventricular arrest 1

3. Risk factors for toxicity:

   • Elderly or debilitated patients 2
   • Patients with cardiac disease 1, 2
   • Hepatic impairment (reduced metabolism) 2
   • Electrolyte disorders 1
   • Renal impairment 2

Diagnostic Workup Algorithm

1. Immediate Assessment (First 5-10 minutes)

• Vital signs with continuous cardiac monitoring

• Focused history:

  • Lidocaine dosage, route, and timing of administration
  • Onset and character of chest pain
  • Associated symptoms (lightheadedness, tinnitus, perioral numbness, altered mental status) 1
  • Pre-existing cardiac conditions

• Physical examination:

  • Cardiovascular exam
  • Neurological status (mental status changes may indicate toxicity)
  • Signs of hypoperfusion

2. Initial Testing (First 30 minutes)

• 12-lead ECG (to assess for arrhythmias or ischemic changes)
• Serum lidocaine level (though correlation with symptoms may be weak) 3
• Basic metabolic panel (electrolyte abnormalities may potentiate toxicity)
• Liver function tests (impaired hepatic function increases toxicity risk)
• Cardiac biomarkers (troponin)
• Arterial blood gas (if respiratory compromise or acidosis suspected)

3. Differential Diagnosis Evaluation

• Cardiac causes:

  • Acute coronary syndrome
  • Stress-induced cardiomyopathy
  • Arrhythmia

• Lidocaine toxicity:

  • Assess for other symptoms in the toxicity spectrum (neurological symptoms often precede cardiac symptoms)
  • Note: The relief of chest pain by a "GI cocktail" (containing viscous lidocaine) does not rule out cardiac causes 1

• Non-cardiac causes:

  • Pulmonary (PE, pneumothorax)
  • Gastrointestinal
  • Musculoskeletal

4. Management Approach

• Discontinue lidocaine if toxicity is suspected 1
• Supportive care with oxygen and IV fluids
• Treat arrhythmias if present
• For severe toxicity:
  • Have 20% lipid emulsion available for treatment 4
  • Resuscitation equipment and personnel should be immediately available 2

Special Considerations

Route of Administration Matters

• IV administration: Higher risk of toxicity with rapid onset

  • Bolus doses should be carefully calculated based on ideal body weight 1
  • Maximum safe dose: 4.5 mg/kg without epinephrine, 7.0 mg/kg with epinephrine 4

• Topical/local administration: Lower risk but still possible with excessive use

  • Systemic absorption can still occur, especially with mucosal application 2

Common Pitfalls to Avoid

1. Assuming chest pain in a patient on lidocaine is always due to the underlying condition

   • Lidocaine itself can cause cardiac symptoms that mimic the condition being treated

2. Overlooking early warning signs of toxicity

   • Neurological symptoms (lightheadedness, tinnitus, perioral numbness) often precede cardiac toxicity 1, 2

3. Relying on serum lidocaine levels alone

   • Levels correlate only weakly with toxicity symptoms 3

4. Failure to recognize high-risk patients

   • Elderly, cardiac disease, hepatic/renal impairment, and electrolyte disorders increase risk 1, 2

5. Confusing relief of pain with "GI cocktail" as diagnostic

   • Relief of chest pain with a mixture containing lidocaine does not rule out cardiac causes 1

By following this systematic approach, clinicians can effectively evaluate chest pain in patients taking lidocaine, distinguishing between lidocaine toxicity and other potential causes while ensuring patient safety.