What is the starting dose of isoproterenol for adults with bradycardia?

Isoproterenol Starting Dose for Adult Bradycardia

The American Heart Association recommends starting isoproterenol at 2-10 mcg/min IV infusion, titrated based on heart rate and blood pressure response. 1

Dosing Specifications

• Standard ACLS dosing is 2-10 mcg/min as a continuous IV infusion for symptomatic bradycardia, as recommended by the American Heart Association 1

• The American College of Cardiology describes a broader dosing range of 1-20 mcg/min IV for bradycardia management, with titration based on heart rate response 1

• An alternative bolus dosing strategy of 20-60 mcg IV followed by 10-20 mcg boluses can be used, though continuous infusion is more commonly employed 2

Critical Context: When to Use Isoproterenol

Isoproterenol is a second-line agent that should only be used after atropine has failed (0.5-1 mg IV, repeated every 3-5 minutes up to maximum 3 mg total), as recommended by the American College of Cardiology 1, 2

Treatment Algorithm for Symptomatic Bradycardia:

1. First-line: Atropine 0.5-1 mg IV, repeat every 3-5 minutes to maximum 3 mg 2

2. If atropine fails: Consider transcutaneous pacing AND/OR start chronotropic infusion 2

3. Chronotropic options (in order of preference):

   • Dopamine 5-10 mcg/kg/min (preferred for most patients) 2
   • Epinephrine 2-10 mcg/min (preferred if severe hypotension or strong inotropic support needed) 2
   • Isoproterenol 2-10 mcg/min (preferred ONLY if no concern for ischemia) 1, 2

Absolute Contraindication: Coronary Ischemia

Any concern for coronary ischemia is an absolute contraindication to isoproterenol. The American College of Cardiology warns that isoproterenol increases myocardial oxygen demand through beta-1 effects while simultaneously decreasing coronary perfusion through beta-2 vasodilatory effects, worsening the oxygen supply-demand mismatch 1

• The American Heart Association advises against using isoproterenol in acute coronary syndromes or suspected ischemia 1

• Increasing heart rate with any chronotropic agent in acute MI may worsen ischemia or increase infarct size 2

Special Population: Post-Heart Transplant Patients

Isoproterenol is the preferred chronotropic agent for post-heart transplant patients because atropine may cause paradoxical heart block or sinus arrest in 20% of transplant patients due to denervated hearts 1, 2

Monitoring and Titration

• The American College of Cardiology recommends carefully monitoring heart rate, blood pressure, and ECG during isoproterenol administration 1

• Titrate the infusion every few minutes based on heart rate response and hemodynamic parameters 1

• Higher doses (>20 mcg/min) may result in vasoconstriction or arrhythmias 1

Evidence Quality Warning

The American College of Cardiology states that there is no clinical trial or observational series supporting the use of isoproterenol for bradycardia treatment, despite numerous case reports 1

• Isoproterenol failed to improve survival in cardiac arrest in randomized controlled trials 1

• The recommendation is based primarily on physiologic rationale and case reports rather than high-quality evidence 1

Common Pitfalls to Avoid

• Do not use isoproterenol as primary therapy for unstable bradycardia—atropine, pacing, or other pressors (dopamine, epinephrine) are preferred 1

• Do not delay transcutaneous pacing while attempting pharmacologic therapy in hemodynamically unstable patients 2

• Do not use doses <0.5 mg of atropine, as they may paradoxically decrease heart rate further 2

• Do not use isoproterenol in cardiac arrest—it provides no benefit for return of spontaneous circulation or survival 1