What medication can be used to increase heart rate in a patient with symptomatic bradycardia?

Medications to Increase Heart Rate in Symptomatic Bradycardia

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

First-Line Treatment: Atropine

Atropine should be administered immediately for patients with bradycardia causing symptoms or hemodynamic compromise (altered mental status, chest pain, heart failure, hypotension, or shock). 1

• Dosing: 0.5-1 mg IV bolus, repeat every 3-5 minutes as needed 1
• Maximum total dose: 3 mg 1
• Mechanism: Blocks muscarinic acetylcholine receptors, facilitating sinoatrial conduction and increasing sinus node automaticity 1
• Half-life: Approximately 2 hours 1

Critical Atropine Warnings

Avoid doses less than 0.5 mg, as paradoxical further slowing of heart rate may occur. 1

Atropine is contraindicated in heart transplant patients without autonomic reinnervation, as it may cause paradoxical high-degree AV block or sinus arrest. 1

Atropine is likely effective for sinus bradycardia and AV nodal block, but may be ineffective for type II second-degree or third-degree AV block with wide QRS complexes where the block is infranodal. 1

Second-Line Medications: Catecholamines

If bradycardia persists despite atropine, initiate IV infusion of beta-adrenergic agonists. 1, 2

Dopamine (Preferred Second-Line Agent)

Dopamine 5-20 mcg/kg/min IV provides dose-dependent chronotropic and inotropic effects. 1

• Starting dose: 5 mcg/kg/min IV 1
• Titration: Increase by 5 mcg/kg/min every 2 minutes based on response 1
• Maximum dose: 20 mcg/kg/min 1
• Mechanism: Mixed alpha-adrenergic, beta-adrenergic, and dopaminergic effects 1
• At 1-2 mcg/kg/min: Predominantly vasodilatory effects 1
• At 5-20 mcg/kg/min: Enhanced chronotropy and inotropy predominate 1

Critical warning: Doses exceeding 20 mcg/kg/min may cause profound vasoconstriction and proarrhythmias. 1

Epinephrine (Alternative Second-Line Agent)

Epinephrine 2-10 mcg/min IV or 0.1-0.5 mcg/kg/min IV, titrated to desired effect. 1

• Mechanism: Strong alpha-adrenergic and beta-adrenergic effects 1
• Use when: Severe hypotension with bradycardia requires both strong chronotropic and inotropic support 2
• Preferred in: Heart transplant patients (where atropine is contraindicated) 2

Isoproterenol (Alternative Agent)

Isoproterenol 20-60 mcg IV bolus followed by 10-20 mcg doses, or infusion of 1-20 mcg/min based on heart rate response. 1

• Mechanism: Nonselective beta agonist with chronotropic and inotropic effects without vasopressor effect 1
• Advantage: Provides chronotropy without vasoconstriction 2
• Critical warning: Monitor for ischemic chest pain; use with caution in patients at risk for coronary ischemia 1

Special Situation Medications

Beta-Blocker or Calcium Channel Blocker Overdose

For calcium channel blocker overdose causing symptomatic bradycardia, intravenous calcium is reasonable. 1

• 10% calcium chloride: 1-2 g IV every 10-20 minutes or infusion of 0.2-0.4 mL/kg/h 1
• 10% calcium gluconate: 3-6 g IV every 10-20 minutes or infusion of 0.6-1.2 mL/kg/h 1

Glucagon is reasonable for beta-blocker or calcium channel blocker overdose. 1

• Dose: 3-10 mg IV bolus over 3-5 minutes, followed by infusion of 3-5 mg/h 1
• Mechanism: Activates hepatic adenyl cyclase, counteracting beta-blocker effects 1
• Side effects: Nausea and vomiting (concerning if airway protection compromised) 1

High-dose insulin therapy is reasonable for severe beta-blocker or calcium channel blocker toxicity. 1

• Dose: 1 unit/kg IV bolus followed by 0.5 units/kg/h infusion 1
• Evidence: Associated with improved heart rate, hemodynamics, and mortality 1
• Side effects: Hypoglycemia and hypokalemia (usually mild); monitor glucose and potassium closely 1

Digoxin Toxicity

Digoxin Fab antibody fragment is reasonable for symptomatic bradycardia from digoxin toxicity. 1

• Dosing: Dependent on amount ingested or known digoxin concentration 1
• One vial binds approximately 0.5 mg digoxin 1
• Administration: Over at least 30 minutes; may be repeated 1

Post-Heart Transplant or Spinal Cord Injury

Aminophylline or theophylline is reasonable for bradycardia in post-heart transplant patients or acute spinal cord injury. 1

• Aminophylline: 6 mg/kg in 100-200 mL IV over 20-30 minutes, or 250 mg IV bolus 1
• Theophylline: 300 mg IV followed by oral 5-10 mg/kg/day titrated to effect 1
• Mechanism: Methylxanthines inhibit suppressive effects of adenosine on sinoatrial node 1
• Target serum levels: 10-20 mcg/mL (though effective doses in spinal cord injury often achieve levels below this range) 1
• Monitoring: Continuous cardiac monitoring mandatory during IV infusion to detect arrhythmias 3

Treatment Algorithm

1. Assess for hemodynamic instability: Altered mental status, chest pain, heart failure, hypotension (SBP <90 mmHg), or shock 1, 2

2. Identify and treat reversible causes: Medications (beta-blockers, calcium channel blockers, digoxin), electrolyte abnormalities (hyperkalemia, hypokalemia), hypothyroidism, hypothermia, hypoxia, acute MI, infections 1

3. Administer atropine 0.5-1 mg IV (unless contraindicated in heart transplant patients) 1

   • Repeat every 3-5 minutes up to maximum 3 mg 1

4. If atropine fails, initiate dopamine 5 mcg/kg/min IV 1, 2

   • Increase by 5 mcg/kg/min every 2 minutes to maximum 20 mcg/kg/min 1, 2
   • Monitor for excessive tachycardia or arrhythmias 1, 2

5. If dopamine ineffective or contraindicated, consider epinephrine 2-10 mcg/min IV 1, 2

   • Alternative: Isoproterenol 1-20 mcg/min infusion 1, 2

6. Consider transcutaneous pacing if pharmacologic therapy fails 2

7. Prepare for transvenous pacing or permanent pacemaker if indicated 2

Common Pitfalls and Caveats

In acute coronary ischemia or MI, increasing heart rate with chronotropic agents may worsen ischemia or increase infarct size. Use atropine cautiously and limit total dose to 0.03-0.04 mg/kg in patients with coronary artery disease. 1, 2

Do not delay transcutaneous pacing in unstable patients while giving additional atropine doses. 2

Atropine is ineffective for infranodal blocks (type II second-degree or third-degree AV block with wide QRS), and failure to respond suggests severe nodal dysfunction requiring pacing. 1, 2

Continuous cardiac monitoring and ideally arterial blood pressure monitoring are essential for all patients requiring vasopressors. 2