Dopamine for Refractory Bradycardia on Norepinephrine
Add dopamine at 5–10 µg/kg/min IV infusion when symptomatic bradycardia persists despite atropine in a patient already receiving norepinephrine. 1
First-Line Treatment: Atropine
Before adding any chronotropic agent, administer atropine 0.5–1 mg IV push, repeating every 3–5 minutes up to a maximum total dose of 3 mg. 1 Doses below 0.5 mg may paradoxically worsen bradycardia and must be avoided. 1
Atropine is most effective for:
- Sinus bradycardia
- First-degree AV block
- Mobitz I (Wenckebach) second-degree AV block
- Vagally mediated inferior MI bradycardia 1
Atropine will not work for:
- Mobitz II second-degree AV block with wide QRS
- Third-degree AV block with wide QRS
- Post-cardiac transplant patients without autonomic reinnervation 1
Second-Line: Dopamine When Atropine Fails
Dopamine is the recommended second-line chronotropic agent for symptomatic bradycardia refractory to atropine, particularly when the patient is already on norepinephrine for shock. 2, 1
Dosing Protocol
- Start at 5 µg/kg/min IV infusion 1
- Titrate by 5 µg/kg/min every 2 minutes based on heart rate and blood pressure response 1
- Therapeutic range: 5–20 µg/kg/min for chronotropic effect 1
- Maximum dose: 20 µg/kg/min—do not exceed this, as higher doses cause excessive vasoconstriction and arrhythmias without additional heart rate benefit 1
At 5–20 µg/kg/min, dopamine provides both chronotropic and inotropic effects through β₁-adrenergic stimulation, making it useful when bradycardia coexists with hypotension or low cardiac output. 1
Why Dopamine Over Other Agents?
Dopamine vs. Epinephrine
Dopamine is preferred over epinephrine in this scenario because:
- Dopamine has more titratable, dose-dependent effects allowing better control 1
- Lower doses provide chronotropy with less vasoconstriction than epinephrine 1
- Epinephrine has strong α-adrenergic effects causing more profound vasoconstriction (dose 2–10 µg/min IV) 1
However, epinephrine is preferred when:
- Severe hypotension demands strong combined chronotropic and vasopressor effects 1
- The patient is a heart transplant recipient (atropine contraindicated) 1
Dopamine vs. Isoproterenol
Isoproterenol may actually be preferable to both dopamine and epinephrine in ischemic cardiomyopathy with bradycardia because it provides chronotropic and inotropic effects without vasopressor effects (dose: 20–60 µg IV bolus or 1–20 µg/min infusion). 1
Critical Safety Warnings
Contraindications
Do not use dopamine in:
- Infranodal AV block (Mobitz II or third-degree with wide QRS)—dopamine does not improve conduction below the AV node and may be harmful; transcutaneous pacing is indicated instead 1
Acute Coronary Syndrome
Use dopamine with extreme caution in acute coronary ischemia or recent MI:
- Dopamine-induced tachycardia increases myocardial oxygen demand and can exacerbate ischemia 1
- Limit heart rate rise to approximately 60 bpm 1
Arrhythmia Risk
Doses >20 µg/kg/min cause:
- Pronounced α-adrenergic vasoconstriction
- Increased afterload
- Pro-arrhythmic events (ventricular tachycardia/fibrillation) 1
Continuous monitoring for chest pain, ST changes, and arrhythmias is required. 1
Compatibility with Norepinephrine
Continuing norepinephrine while adding dopamine is pharmacologically safe—the two agents act via distinct mechanisms and can be given together without interference. 3 However, the combination of dopamine with norepinephrine at doses >5 µg/kg/min produces excessive sympathomimetic stimulation and increases adverse event risk. 3
Safer alternative strategy: If the patient requires both vasopressor support (norepinephrine) and chronotropic support, consider:
- Vasopressin 0.03 units/min added to norepinephrine to reduce norepinephrine dose 3
- Dobutamine 2.5–20 µg/kg/min if persistent hypoperfusion exists despite adequate MAP 3
Transcutaneous Pacing
Do not delay transcutaneous pacing in hemodynamically unstable patients while awaiting response to atropine or dopamine. 1 Transcutaneous pacing carries a Class IIa recommendation as a bridge to transvenous or permanent pacing. 1
Special Clinical Scenarios
Neurogenic Shock (Spinal Cord Injury)
Bradycardia is often refractory to atropine; dopamine 5–20 µg/kg/min (or aminophylline 6 mg/kg IV over 20–30 min) is appropriate. 1
Post-Heart-Transplant Patients
Dopamine is not preferred; aminophylline or theophylline is recommended because atropine is contraindicated and may precipitate high-degree AV block. 1
Monitoring Requirements
- Arterial catheter for continuous blood pressure monitoring 1
- Heart rate and rhythm continuously 1
- Urine output ≥0.5 mL/kg/h 1
- Lactate clearance every 2–4 hours 1
- Mental status and peripheral perfusion 1
Common Pitfalls to Avoid
- Do not exceed dopamine 20 µg/kg/min—higher doses cause excessive vasoconstriction and arrhythmias 1
- Do not start dopamine before attempting atropine—atropine is safer and more appropriate as first-line 1
- Do not use dopamine for infranodal blocks—it will not improve conduction and may be harmful 1
- Do not use low-dose dopamine for "renal protection"—this is strongly contraindicated (Grade 1A) 3