Intravenous Adrenaline Dosing for Unstable Bradycardia
For unstable bradycardia refractory to atropine and transcutaneous pacing, start intravenous adrenaline at 0.1–0.5 mcg/kg/min (equivalent to 7–35 mcg/min in a 70-kg adult), titrating upward to achieve adequate heart rate and perfusion. 1
Dosing Algorithm
The 2010 AHA Guidelines provide the most direct guidance for this specific clinical scenario 1:
- Starting dose: 0.1 mcg/kg/min IV infusion
- Titration range: Up to 0.5 mcg/kg/min based on clinical response
- For a 70-kg adult: This translates to 7–35 mcg/min
- Maximum consideration: Some sources describe titration up to 10 mcg/min in refractory cases 2, though doses above 0.5 mcg/kg/min increase risk of arrhythmias and myocardial ischemia
The 2019 ACC/AHA/HRS Bradycardia Guidelines echo similar dosing: 2–10 mcg/min IV or 0.1–0.5 mcg/kg/min, titrated to desired effect 3, 4.
Clinical Context and Sequencing
Adrenaline is indicated for symptomatic bradycardia only after atropine and transcutaneous pacing have failed or when pacing is unavailable 1. This is critical—adrenaline is not first-line therapy.
Before reaching for adrenaline:
- Atropine should be administered first (0.5–2 mg IV, with doses <0.5 mg potentially causing paradoxical bradycardia) 5
- Transcutaneous pacing should be attempted if available
- The newer 2019 guidelines emphasize transcutaneous pacing over immediate pharmacologic escalation 3, 4
Preparation and Administration
Infusion preparation 2:
- Add 1 mg (1 mL of 1:1000) adrenaline to 250 mL D5W = 4 mcg/mL concentration
- Alternative: 1 mg (1 mL) in 100 mL saline = 10 mcg/mL concentration (1:100,000)
- Administer via central line when possible to avoid tissue necrosis from extravasation 1
Critical Safety Considerations
Adrenaline carries significant risks that mandate careful titration and monitoring:
- Arrhythmias: Doses >20 mcg/kg/min (or >0.5 mcg/kg/min) substantially increase risk of ventricular arrhythmias 3
- Myocardial ischemia: Alpha and beta effects increase myocardial oxygen demand while potentially reducing coronary perfusion 1
- Hypokalemia: Adrenaline causes rapid intracellular potassium shift via β2-adrenergic stimulation, which can precipitate life-threatening arrhythmias, especially with repeated or continuous dosing 6
- Metabolic effects: Increases blood glucose, lactate, and metabolic rate 1
Monitor continuously:
- Cardiac rhythm (ECG)
- Blood pressure every minute initially
- Heart rate response
- Signs of myocardial ischemia (chest pain, ST changes)
- Consider potassium monitoring with prolonged or high-dose infusions 6
Pitfalls to Avoid
Don't use adrenaline as first-line therapy—atropine and pacing come first 1, 3
Don't start at high doses—begin at 0.1 mcg/kg/min and titrate upward only as needed. Starting too high increases arrhythmia risk without proven benefit 3
Don't confuse concentrations—IV adrenaline for bradycardia uses mcg/min dosing (continuous infusion), not the mg bolus dosing used in cardiac arrest 7
Don't ignore alternative causes—if bradycardia persists despite appropriate adrenaline dosing, consider specific etiologies requiring targeted therapy (beta-blocker/calcium channel blocker overdose, digoxin toxicity, hyperkalemia, acute MI) 3, 4
Don't use alkaline solutions in the same IV line—adrenaline is inactivated by sodium bicarbonate and other alkaline solutions 1
Alternative Agents
If adrenaline is contraindicated or ineffective, consider 3, 4:
- Dopamine: 5–20 mcg/kg/min (though higher doses cause vasoconstriction)
- Isoproterenol: 1–20 mcg/min (avoid in ischemic settings due to increased oxygen demand and decreased coronary perfusion)
The evidence base for adrenaline in unstable bradycardia is limited—recommendations are largely extrapolated from post-cardiac arrest care and expert consensus rather than randomized trials specifically in bradycardia 1, 3. Nonetheless, it remains the guideline-recommended chronotropic agent when atropine and pacing fail.