What is the initial approach to managing arrhythmias according to Rosen's emergency medicine?

Initial Approach to Managing Arrhythmias in Emergency Medicine

The initial approach to managing arrhythmias should be based on hemodynamic stability, with immediate cardioversion indicated for unstable patients presenting with tachyarrhythmias, while stable patients can be treated with appropriate pharmacological interventions based on the specific arrhythmia. 1

Assessment of Hemodynamic Stability

First, determine if the patient is hemodynamically stable or unstable:

Signs of Hemodynamic Instability:

• Systolic BP ≤ 90 mmHg
• Altered mental status/decreased consciousness
• Signs of shock or poor perfusion
• Acute chest pain suggesting ischemia
• Acute heart failure
• Heart rate ≥ 150 beats/min with symptoms 1

Management Algorithm Based on Stability

For Hemodynamically Unstable Patients:

1. Tachyarrhythmias:

   • Immediate synchronized cardioversion:
     • Monomorphic VT: 100J synchronized shock 1
     • Polymorphic VT/VF: 200J unsynchronized shock 1
     • Atrial fibrillation: 120-200J biphasic 2
     • Atrial flutter: 50-100J biphasic 2
   • Establish IV access, administer oxygen, and monitor vital signs

2. Bradyarrhythmias:

   • Atropine 0.5 mg IV (may repeat to maximum 3 mg) 1
   • If no response, consider transcutaneous pacing 1
   • Consider epinephrine infusion if pacing unavailable 1

For Hemodynamically Stable Patients:

Narrow Complex Tachycardias (SVT):

1. First-line: Vagal maneuvers (Valsalva, carotid sinus massage) 1
2. Second-line: Adenosine 6 mg rapid IV bolus, followed by 12 mg if needed 1, 2
3. Third-line options:
   • For SVT: IV verapamil 5-10 mg over 60 seconds 1
   • For atrial fibrillation/flutter: Rate control with beta-blockers or calcium channel blockers 2

Wide Complex Tachycardias:

1. Always assume VT if diagnosis is unclear 1
2. For stable monomorphic VT:
   • Amiodarone: 150 mg IV over 10 minutes, followed by infusion of 1 mg/min for 6 hours, then 0.5 mg/min 1, 3
   • Alternative: Procainamide 20-30 mg/min loading infusion (up to 12-17 mg/kg) 1
   • For ischemia-related VT: Consider lidocaine 1.0-1.5 mg/kg bolus 1

Bradyarrhythmias:

1. For symptomatic sinus bradycardia: Atropine 0.5 mg IV, may repeat to maximum 3 mg 1
2. For AV block at nodal level: Atropine may be beneficial 1
3. For infranodal block: Prepare for temporary pacing (atropine ineffective) 1

Special Considerations

Atrial Fibrillation/Flutter:

• Risk stratify based on heart rate and symptoms 1
• For onset <24 hours: Consider cardioversion 1
• For onset >24 hours: Anticoagulate for 3-4 weeks before cardioversion 1

Refractory Ventricular Arrhythmias:

• For VF/pulseless VT refractory to 3 shocks: Amiodarone 300 mg IV bolus 1
• Consider magnesium 8 mmol for refractory VF if hypomagnesemia suspected 1

Common Pitfalls to Avoid:

• Using verapamil in wide-complex tachycardias of unknown origin (can precipitate hemodynamic collapse) 2
• Using more than one antiarrhythmic drug simultaneously (increases proarrhythmic risk) 1
• Administering atropine for infranodal AV block (ineffective and potentially harmful) 1
• Delaying cardioversion in unstable patients while attempting pharmacological therapy 1

Medication Administration Pearls

• Amiodarone IV should be delivered by volumetric infusion pump through a central venous catheter when possible 3
• Adenosine requires rapid bolus administration followed by saline flush due to its extremely short half-life 1
• Lidocaine dosing should be reduced in older patients and those with CHF or hepatic dysfunction 1

By following this structured approach based on hemodynamic stability and specific arrhythmia characteristics, emergency physicians can effectively manage cardiac arrhythmias while minimizing morbidity and mortality.