What are the dosing guidelines for intravenous (IV) beta blockers, such as metoprolol (Lopressor) or esmolol, for immediate heart rate control or blood pressure reduction?

IV Beta Blocker Dosing Guidelines for Heart Rate Control and Blood Pressure Reduction

For immediate heart rate control or blood pressure reduction, esmolol is recommended at a loading dose of 500 mcg/kg IV over 1 minute, followed by a maintenance infusion of 50-300 mcg/kg/min titrated to effect; alternatively, metoprolol can be administered at 2.5-5 mg IV bolus over 2 minutes, repeated up to 3 doses (maximum 15 mg). 1

Esmolol (Ultra-Short Acting Beta Blocker)

Dosing for Supraventricular Tachycardia (SVT) or Heart Rate Control:

• Loading dose: 500 mcg/kg IV over 1 minute
• Initial maintenance: 50 mcg/kg/min for 4 minutes
• Titration: Adjust dose as needed at ≥4-minute intervals
• Maximum dose: 200 mcg/kg/min for tachycardia, 300 mcg/kg/min for hypertension 1, 2

Advantages:

• Ultra-short half-life (2-9 minutes)
• Rapid onset (1-2 minutes)
• Quick offset if adverse effects occur
• Safer in patients with relative contraindications to beta blockade 3

Metoprolol (Selective Beta-1 Blocker)

Dosing for Heart Rate Control:

• Initial dose: 2.5-5 mg IV bolus over 2 minutes
• Repeat: May repeat every 5 minutes up to maximum 15 mg
• Onset: 5 minutes
• Follow-up: Can transition to oral therapy (25-100 mg twice daily) 1, 4

Specific Situations:

• Acute MI: Three 5 mg IV boluses at 2-minute intervals, followed by oral therapy 15 minutes after last IV dose 4
• Aortic dissection: Target heart rate ≤60 bpm and systolic BP ≤120 mmHg 1

Propranolol (Non-Selective Beta Blocker)

Dosing:

• Initial dose: 0.15 mg/kg IV
• Onset: 5 minutes
• Oral follow-up: 80-240 mg daily in divided doses 1

Clinical Decision-Making Algorithm

1. Assess patient for contraindications:

   • Severe bradycardia
   • Heart block greater than first degree
   • Cardiogenic shock
   • Decompensated heart failure
   • Severe bronchospastic disease 1, 2

2. Select appropriate agent based on clinical scenario:

   • Need for ultra-short duration: Choose esmolol
   • Acute aortic dissection: Esmolol or metoprolol (target HR ≤60 bpm)
   • Atrial fibrillation with WPW syndrome: AVOID beta blockers 1
   • Patients with asthma/COPD: Prefer cardioselective agents (esmolol, metoprolol) at low doses 5

3. Monitoring requirements:

   • Continuous ECG monitoring
   • Blood pressure every 5-15 minutes during titration
   • Respiratory status
   • Signs of heart failure 1, 6

Special Considerations

Cautions:

• Hypotension: More common with esmolol (9.3%) than metoprolol (3.8%) immediately after administration 7
• Elderly patients: May require lower doses due to increased sensitivity 6
• Pulmonary disease: Use cardioselective agents (metoprolol, esmolol) with caution; have bronchodilators available 5

Transition to Oral Therapy:

• For metoprolol IV to oral conversion: 15 mg IV ≈ 50 mg oral metoprolol tartrate every 6 hours 4
• Begin oral therapy 15 minutes after last IV dose if patient is stable 4

Efficacy Considerations

• Esmolol may achieve target heart rate control more effectively than metoprolol (89% vs 78% achieving HR ≤65 bpm) 7
• For multifocal atrial tachycardia, metoprolol has shown 68% conversion to sinus rhythm with mean IV dose of 6.5 mg 8

Remember that IV beta blockers require close monitoring for adverse effects including bradycardia, hypotension, and heart failure. Always have resuscitation equipment readily available when administering these medications.