What is the management of bradycardia (abnormally slow heart rate) in the Intensive Care Unit (ICU)?

Management of Bradycardia in the ICU

Bradycardia in the ICU should be managed with atropine as first-line therapy for symptomatic patients, followed by beta-adrenergic agonists or temporary pacing for refractory cases, with permanent pacing reserved for persistent high-grade conduction disorders.

Initial Assessment and Management

Defining Bradycardia

• Heart rate < 60 beats per minute
• Focus on identifying whether the bradycardia is symptomatic or hemodynamically significant

Symptoms and Signs of Hemodynamic Compromise

• Acute altered mental status
• Ischemic chest discomfort
• Acute heart failure
• Hypotension
• Other signs of shock 1

Treatment Algorithm for Symptomatic Bradycardia

First-Line Therapy

1. Atropine
   • Dosage: 0.5-1 mg IV every 3-5 minutes (maximum total dose 3 mg) 1, 2
   • Mechanism: Blocks muscarinic acetylcholine receptors, enhancing sinoatrial node automaticity 2
   • Efficacy: Approximately 50% of patients with symptomatic bradycardia show partial or complete response 3

Second-Line Therapies (if bradycardia persists after atropine)

1. Dopamine

   • Dosage: 5-20 mcg/kg/min IV infusion 1
   • Start at 5 mcg/kg/min and increase by 5 mcg/kg/min every 2 minutes as needed 1
   • Monitor for potential vasoconstriction or arrhythmias at doses >20 mcg/kg/min 1

2. Epinephrine

   • Dosage: 2-10 mcg/min IV or 0.1-0.5 mcg/kg/min IV titrated to desired effect 1
   • Strong alpha and beta-adrenergic effects that increase chronotropy and inotropy 1

3. Isoproterenol

   • Dosage: 20-60 mcg IV bolus followed by 10-20 mcg, or infusion of 1-20 mcg/min 1
   • Non-selective beta-agonist with chronotropic and inotropic effects 1
   • Caution: Avoid in settings where coronary ischemia is a concern 1

4. Transcutaneous Pacing (TCP)

   • Indicated for patients unresponsive to atropine 1
   • Reasonable to initiate in unstable patients not responding to pharmacological therapy 1

5. Transvenous Pacing

   • Consider if patient does not respond to drugs or TCP 1
   • Indicated for persistent high-grade AV block 1

Special Considerations

Etiology-Specific Management

1. 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
   • Monitor glucose and potassium levels closely 1

2. Calcium Channel Blocker Overdose

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

3. Acute Myocardial Infarction

   • Temporary pacing is indicated for medically refractory symptomatic bradycardia 1
   • Important: Observe a waiting period before determining need for permanent pacing 1
   • Permanent pacing indicated for persistent high-grade AV block after waiting period 1
   • Caution: Atropine may be less effective in inferior MI with AV block at the His-Purkinje level 4

Patient-Specific Considerations

1. Heart Transplant Patients

   • Do not use atropine in heart transplant patients without evidence of autonomic reinnervation 1
   • Alternative agents: Aminophylline (6 mg/kg in 100-200 mL IV over 20-30 min) or theophylline 1, 5

2. Elderly Patients

   • Elimination half-life of atropine is more than doubled in elderly patients (>65 years) 2
   • May require dose adjustment and closer monitoring 5

Potential Complications and Pitfalls

Atropine-Related Complications

• Paradoxical bradycardia with low doses (<0.5 mg) 1
• Ventricular tachycardia or fibrillation (rare) 6
• Sustained sinus tachycardia 6
• Increased premature ventricular contractions 6
• Toxic psychosis at high doses 6
• Critical warning: Paradoxical worsening of bradycardia can occur in patients with infranodal heart blocks (His-Purkinje level) 4

Monitoring Requirements

• Continuous cardiac monitoring is essential during and after treatment
• Regular assessment of blood pressure and perfusion status
• Be prepared for rapid escalation of therapy if initial treatments fail

When to Consider Permanent Pacing

• Persistent second-degree Mobitz type II AV block
• High-grade AV block
• Third-degree AV block not expected to resolve 1
• Symptomatic bradycardia related to AV block 1

Important Clinical Pearls

• Not all bradycardia requires immediate intervention; focus on symptoms and hemodynamic stability 7
• Adverse effects of atropine correlate with higher initial doses (>1.0 mg) or cumulative doses exceeding 2.5 mg over 2.5 hours 6
• Bradycardia in the setting of acute MI often resolves; avoid permanent pacing for transient AV block 1
• Be prepared for delayed onset of bradycardia in certain toxicological cases (e.g., fingolimod overdose) 8

By following this evidence-based approach to bradycardia management in the ICU, clinicians can effectively address this common but potentially serious condition while minimizing complications and optimizing patient outcomes.