What is the recommended EKG (electrocardiogram) protocol for an Elavil (amitriptyline) overdose?

EKG Protocol for Amitriptyline (Elavil) Overdose

In patients with suspected amitriptyline overdose, an immediate 12-lead ECG should be obtained and continuous cardiac monitoring initiated to assess for life-threatening arrhythmias and guide management. 1, 2

Initial ECG Assessment

Critical ECG Parameters to Evaluate:

• QRS duration:

  • QRS ≥ 100 ms is common in TCA overdose (present in 82% of cases) 3
  • QRS > 120 ms has stronger association with arrhythmias (OR 4.83) 3
  • QRS ≥ 160 ms indicates severe toxicity 2

• QT/QTc interval:

  • QTc > 500 ms is associated with increased arrhythmia risk (OR 3.07) 3
  • Document QTc before and after treatment interventions 1

• Lead aVR findings:

  • R wave amplitude ≥ 3 mm in aVR (sensitivity 81% for predicting seizures/arrhythmias) 4
  • R/S ratio > 0.7 in aVR (strongest predictor, OR 16) 3, 4
  • Rightward axis shift in terminal QRS complex 2

• Other ECG abnormalities:

  • Sinus tachycardia (present in 57.7% of pediatric cases) 5
  • ST-T wave changes 2
  • QT-U distortion, T wave alternans, enhanced U waves 1

Monitoring Protocol

1. Immediate monitoring:

   • Obtain baseline 12-lead ECG immediately upon presentation 2
   • Initiate continuous cardiac monitoring 2

2. Serial ECG assessment:

   • Document QTc in medical record using rhythm strip before treatment initiation 1
   • Repeat ECG at least every 8 hours during treatment 1
   • Additional ECGs after any change in clinical status or treatment interventions 1

3. Duration of monitoring:

   • Continue ECG monitoring until drug levels have decreased and evidence of QT prolongation or associated arrhythmias is no longer present 1
   • Minimum six hours of observation with cardiac monitoring is necessary 2
   • Extended monitoring required if signs of toxicity occur at any time during the period 2

Management Based on ECG Findings

• For QRS ≥ 0.10 seconds (indicating severity of overdose):

  • Administer IV sodium bicarbonate to maintain serum pH 7.45-7.55 2
  • Consider hyperventilation with frequent pH monitoring (avoid pH > 7.60) 2

• For dysrhythmias unresponsive to sodium bicarbonate:

  • Consider lidocaine, bretylium, or phenytoin 2
  • Avoid Type 1A and 1C antiarrhythmics (e.g., quinidine, disopyramide, procainamide) 2

• For Torsades de Pointes:

  • Administer IV magnesium sulfate 1
  • Replete potassium to 4.5-5 mEq/L 1
  • Consider ventricular pacing or isoproterenol for recurrent episodes 1

Special Considerations

• ECG measurements alone should not be used as the sole criteria for risk assessment in TCA overdose 3
• The predictive value of QRS ≥ 100 ms alone is limited (positive predictive value only 35%) 4
• QRS > 120 ms has a 100% positive predictive value for coma in pediatric patients 5
• R wave in aVR < 3 mm has a 100% negative predictive value for seizures in children 5
• Case reports exist of patients succumbing to fatal dysrhythmias late after overdose, necessitating extended monitoring 2

Pitfalls to Avoid

• Do not rely solely on plasma drug levels to guide management 2
• Do not use QRS ≥ 100 ms or QRS ≥ 160 ms as the only predictor of arrhythmias 3
• Do not discontinue monitoring prematurely, even if initial ECG appears normal
• Do not transport patients with significant ECG abnormalities away from monitored settings 6
• Do not use Type 1A and 1C antiarrhythmics (e.g., quinidine, disopyramide, procainamide) as they are contraindicated 2

By following this protocol, clinicians can effectively identify patients at highest risk for life-threatening arrhythmias and provide appropriate interventions to reduce morbidity and mortality in amitriptyline overdose.