What are the quick reference dosing guidelines for drugs used to treat symptomatic bradycardia, tachycardia, and hypertension?

Quick Reference Dosing for Symptomatic Bradycardia, Tachycardia, and Hypertension

Symptomatic Bradycardia

For symptomatic bradycardia (heart rate <50 bpm with hypotension, ischemia, or escape rhythms), atropine 0.5-1 mg IV is the first-line treatment, repeated every 3-5 minutes to a maximum total dose of 1.5-3 mg 1.

Atropine Dosing Algorithm:

• Initial dose: 0.5-1 mg IV push 1
• Repeat: Every 3-5 minutes as needed
• Maximum total: 1.5-3 mg 2, 1
• Critical warning: Doses <0.5 mg may paradoxically slow heart rate 3
• Contraindication: Do NOT use in heart transplant patients without autonomic reinnervation (may cause paradoxical AV block) 1

Second-Line Agents (if atropine fails or contraindicated):

Dopamine 1:

• Start: 5 mcg/kg/min IV
• Titrate: Increase by 5 mcg/kg/min every 2 minutes
• Range: 5-20 mcg/kg/min
• Warning: Doses >20 mcg/kg/min cause vasoconstriction

Epinephrine 1:

• Dose: 2-10 mcg/min IV (or 0.1-0.5 mcg/kg/min)
• Titrate to desired heart rate effect

Isoproterenol 1:

• Bolus: 20-60 mcg IV, then 10-20 mcg increments
• OR infusion: 1-20 mcg/min
• Avoid if coronary ischemia suspected (increases oxygen demand while decreasing coronary perfusion)

Special Situations:

Post-heart transplant or spinal cord injury 1:

• Aminophylline: 6 mg/kg in 100-200 mL IV over 20-30 minutes
• Theophylline: 300 mg IV, then 5-10 mg/kg/day orally (target levels 10-20 mcg/mL)

Beta-blocker/calcium channel blocker overdose 1:

• Calcium chloride 10%: 1-2 g IV every 10-20 minutes OR infusion 0.2-0.4 mL/kg/h
• Glucagon: 3-10 mg IV bolus, then infusion 3-5 mg/h
• High-dose insulin: 1 unit/kg IV bolus, then 0.5 units/kg/h (monitor glucose/potassium closely)

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Ventricular Tachycardia (Hemodynamically Stable)

For stable monomorphic VT, lidocaine is first-line pharmacologic therapy, with procainamide or amiodarone as alternatives 3.

Lidocaine 3:

• Loading: 1.0-1.5 mg/kg IV bolus
• Supplemental boluses: 0.5-0.75 mg/kg every 5-10 minutes
• Maximum loading: 3 mg/kg total
• Maintenance infusion: 2-4 mg/min (30-50 mcg/kg/min)
• Reduce dose: In elderly, CHF, or hepatic dysfunction

Procainamide 3:

• Loading: 20-30 mg/min infusion
• Maximum: 12-17 mg/kg
• Maintenance: 1-4 mg/min
• Reduce dose: In renal dysfunction

Amiodarone 3, 4:

• Loading: 150 mg IV over 10 minutes
• Maintenance: 1.0 mg/min for 6 hours, then 0.5 mg/min
• Pediatric (pulseless VT): 5 mg/kg rapid bolus (max 300 mg), may repeat to 15 mg/kg/day 4

Cardioversion Thresholds:

• Immediate cardioversion: Polymorphic VT (200 J unsynchronized) or hemodynamic instability
• Synchronized cardioversion: Monomorphic VT >150 bpm (100 J)
• Consider medications first: VT <150 bpm with stable hemodynamics 3

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Hypertensive Emergencies

For acute severe hypertension with end-organ damage, IV nicardipine or labetalol are preferred first-line agents, with drug selection based on specific clinical scenario 5, 6, 5.

Nicardipine 5, 6, 5:

• Start: 5 mg/h IV infusion
• Titrate: Increase by 2.5 mg every 5-15 minutes
• Maximum: 15 mg/h
• Advantages: Predictable, titratable, no reflex tachycardia with urapidil alternative

Labetalol 5, 6, 5, 7:

• Bolus: 10-20 mg IV, then 20-80 mg every 10-30 minutes
• Maximum cumulative: 300 mg
• OR infusion: 0.5-2 mg/min, titrate to 2-4 mg/min until goal BP, then 5-20 mg/h
• Contraindications: Asthma, heart block, bradycardia, decompensated heart failure

Clinical Scenario-Specific Choices:

Acute coronary syndrome 5:

• Preferred: Nitroglycerin 5-200 mcg/min (increase by 5 mcg/min every 5 minutes) OR labetalol
• Avoid: Nitroprusside (decreases regional coronary flow, increases myocardial damage)

Acute pulmonary edema 5:

• First choice: Nitroprusside 0.3-10 mcg/kg/min (increase by 0.5 mcg/kg/min every 5 minutes)
• Alternative: Nitroglycerin (may require high doses >200 mcg/min)
• Add: Loop diuretics

Acute aortic dissection 5:

• Target: SBP ≤120 mmHg AND HR ≤60 bpm
• First-line: Esmolol (0.5-1 mg/kg bolus, then 50-300 mcg/kg/min) PLUS nitroprusside or clevidipine
• Alternative: Metoprolol 2.5-5 mg IV every 5 minutes (max 15 mg) or labetalol

Eclampsia/severe preeclampsia 7:

• Labetalol: 10-20 mg IV, then 20-80 mg every 10-30 minutes (max 300 mg cumulative)
• Hydralazine: 5 mg IV/IM, then 5-10 mg every 20-40 minutes (max 20 mg)
• Nifedipine immediate-release: 10-20 mg PO, repeat in 20 minutes if needed (max 180 mg/day)

Other IV Antihypertensive Options:

Clevidipine 5, 6, 5:

• Start: 1-2 mg/h, double every 90 seconds initially
• Maximum: 32 mg/h (max duration 72 hours)
• Contraindicated: Soy/egg allergy, lipid disorders

Esmolol 5, 6, 5:

• Loading: 500-1000 mcg/kg over 1 minute
• Infusion: 50 mcg/kg/min, increase by 50 mcg/kg/min increments
• Maximum: 200 mcg/kg/min

Nitroprusside 5, 6, 5:

• Start: 0.3-0.5 mcg/kg/min
• Titrate: Increase by 0.5 mcg/kg/min every 5 minutes
• Maximum: 10 mcg/kg/min
• Critical warning: Cyanide toxicity with prolonged use or rates >4 mcg/kg/min >30 minutes; consider thiosulfate coadministration

Fenoldopam 5, 6, 5:

• Start: 0.1-0.3 mcg/kg/min
• Titrate: Increase by 0.05-0.1 mcg/kg/min every 15 minutes
• Maximum: 1.6 mcg/kg/min

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Critical Pitfalls to Avoid

1. Never give atropine <0.5 mg - may cause paradoxical bradycardia 3
2. Never use atropine in heart transplant patients without documented autonomic reinnervation 1
3. Avoid isoproterenol if coronary ischemia suspected - worsens oxygen supply-demand mismatch 1
4. Do not use nitroprusside in acute MI - steals coronary blood flow 5
5. Reduce lidocaine infusion rates in elderly, CHF, or liver disease to prevent toxicity 3
6. Monitor for cyanide toxicity with nitroprusside infusions >30 minutes or >4 mcg/kg/min 5, 6
7. Avoid labetalol in asthma, heart block, or decompensated HF 5, 6, 5