What are the recommended IV medications to raise heart rate (HR) in symptomatic bradycardia?

IV Medications for Symptomatic Bradycardia

Atropine is the first-line IV medication for symptomatic bradycardia at a dose of 0.5-1 mg IV, which may be repeated every 3-5 minutes to a maximum dose of 3 mg. 1

First-Line Treatment

Atropine

• Dosage: 0.5-1 mg IV (may be repeated every 3-5 minutes to a maximum of 3 mg) 1
• Mechanism: Blocks parasympathetic influences on the heart, increasing heart rate and improving AV conduction 2
• Indications: Symptomatic sinus bradycardia or AV block with hemodynamic compromise 1
• Efficacy: Approximately 50% of patients with hemodynamically unstable bradycardia have either partial or complete response to atropine therapy 3
• Cautions:
  • Doses <0.5 mg may paradoxically worsen bradycardia 1, 4
  • Use cautiously in acute coronary ischemia/MI as increased heart rate may worsen ischemia 1
  • Contraindicated in heart transplant patients without evidence of autonomic reinnervation 1

Second-Line Treatments

If atropine is ineffective or contraindicated, the following medications may be considered:

1. Dopamine

• Dosage: 5-20 mcg/kg/min IV, starting at 5 mcg/kg/min and increasing by 5 mcg/kg/min every 2 minutes 1
• Caution: Doses >20 mcg/kg/min may cause vasoconstriction or arrhythmias 1

2. Isoproterenol

• Dosage: 20-60 mcg IV bolus followed by doses of 10-20 mcg, or infusion of 1-20 mcg/min based on heart rate response 1
• Best for: Patients at low likelihood of coronary ischemia 1

3. Epinephrine

• Dosage: 2-10 mcg/min IV or 0.1-0.5 mcg/kg/min IV titrated to desired effect 1
• Mechanism: Acts on both alpha and beta-adrenergic receptors, increasing heart rate (positive chronotropic action) 5
• Onset: <5 minutes with IV administration 5

Special Clinical Scenarios

Heart Transplant Patients

• Do not use atropine - ineffective due to lack of vagal innervation 1
• Alternative: Aminophylline 6 mg/kg in 100-200 mL IV fluid over 20-30 minutes 1
• Maintenance: Theophylline 300 mg IV, followed by oral dose of 5-10 mg/kg/day 1

Second or Third-Degree AV Block with Acute Inferior MI

• Consider: Aminophylline 250 mg IV bolus 1
• Note: Atropine may improve AV conduction in 85% of patients with acute inferior MI and high-degree AV block 6

Beta-Blocker or Calcium Channel Blocker Overdose

• Glucagon: 3-10 mg IV with infusion of 3-5 mg/h 1
• High-dose insulin therapy: IV bolus of 1 unit/kg followed by infusion of 0.5 units/kg/h 1

Treatment Algorithm

1. Assess: Confirm symptomatic bradycardia (HR <60 bpm with symptoms or hemodynamic compromise)
2. Identify and treat reversible causes (medications, electrolyte abnormalities, hypothyroidism, etc.) 1, 7
3. First-line treatment: Atropine 0.5-1 mg IV (may repeat q3-5min, max 3 mg) 1
4. If inadequate response to atropine:
   • For patients without risk of coronary ischemia: Isoproterenol
   • For most patients: Dopamine or epinephrine infusion
   • Consider transcutaneous pacing as a bridge to transvenous pacing 1
5. If persistent symptomatic bradycardia: Prepare for temporary or permanent pacing 8

Common Pitfalls

1. Low-dose atropine paradox: Doses <0.5 mg may worsen bradycardia 1
2. Heart transplant error: Atropine is ineffective and potentially harmful in heart transplant patients 1
3. Delayed escalation: Don't delay implementation of external pacing for patients with poor perfusion if medications are ineffective 1
4. Overlooking reversible causes: Always identify and treat underlying causes (medications, electrolytes, hypothyroidism) 7
5. Inappropriate use in high-degree AV blocks: Atropine may be ineffective in type II second-degree or third-degree AV block with new wide-QRS complex 1

By following this evidence-based approach to managing symptomatic bradycardia, you can effectively increase heart rate and improve hemodynamic stability while preparing for more definitive treatment if necessary.