Initial Management for Bradycardia in ACLS
The initial management for symptomatic bradycardia in ACLS is to administer atropine 0.5-1 mg IV, which can be repeated every 3-5 minutes to a maximum total dose of 3 mg. 1, 2
Assessment and Initial Steps
- First, evaluate if bradycardia is causing symptoms or hemodynamic compromise (altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or other signs of shock) 2
- Maintain patent airway and assist breathing as necessary 2
- Provide supplemental oxygen if the patient is hypoxemic 2
- Establish cardiac monitoring to identify rhythm, monitor blood pressure, and measure oxygen saturation 2
- Establish IV access for medication administration 2
- Obtain a 12-lead ECG if available 2
- Identify and treat underlying reversible causes 2
Pharmacological Management
First-Line Treatment: Atropine
- Administer atropine 0.5-1 mg IV for symptomatic bradycardia 1
- Repeat every 3-5 minutes as needed up to a maximum total dose of 3 mg 1, 2
- Doses of atropine <0.5 mg may paradoxically result in further slowing of heart rate and should be avoided 1
- Atropine reverses decreases in heart rate, systemic vascular resistance, and blood pressure mediated by parasympathetic (cholinergic) activity 1, 3
- Atropine is most effective for sinus bradycardia occurring within 6 hours of onset of symptoms of acute MI 1
If Bradycardia Persists Despite Atropine
- Initiate IV infusion of β-adrenergic agonists 1, 2:
- Dopamine: 5-20 mcg/kg/min IV, starting at 5 mcg/kg/min and increasing by 5 mcg/kg/min every 2 minutes 1
- Epinephrine: 2-10 mcg/min IV or 0.1-0.5 mcg/kg/min IV titrated to desired effect 1
- Isoproterenol: 20-60 mcg IV bolus followed by doses of 10-20 mcg, or infusion of 1-20 mcg/min based on heart rate response 1
Pacing Considerations
- Consider transcutaneous pacing (TCP) in unstable patients who do not respond to atropine 1, 2
- TCP is a temporizing measure and can be painful in conscious patients 1
- Prepare for transvenous pacing if the patient does not respond to drugs or TCP 1
- Indications for temporary pacing include 1:
- Sinus bradycardia with symptoms of hypotension unresponsive to drug therapy
- Symptomatic bradycardia not responsive to atropine
- Bilateral bundle branch block
- New or indeterminate age bifascicular block with first-degree AV block
- Mobitz type II second-degree AV block
Special Considerations
Type of AV Block
- Atropine is likely to be effective in sinus bradycardia, conduction block at the level of the AV node, or sinus arrest 1, 2
- Atropine may be ineffective in type II second-degree or third-degree AV block with new wide-QRS complex where the block is likely in non-nodal tissue 1, 2
- For these cases, consider immediate pacing rather than multiple doses of atropine 1
Specific Clinical Scenarios
- Avoid atropine in heart transplant patients without evidence of autonomic reinnervation, as it may cause paradoxical high-degree AV block 1
- Use atropine cautiously in inferior myocardial infarction as increased heart rate may worsen ischemia or increase infarction size 1, 2
- For bradycardia associated with beta-blocker or calcium channel blocker overdose, consider glucagon (3-10 mg IV with infusion of 3-5 mg/h) 1
- For BRASH syndrome (Bradycardia, Renal failure, AV nodal blockade, Shock, and Hyperkalemia), treatment should focus on correcting hyperkalemia and improving renal function 4, 5
Potential Complications and Pitfalls
- Atropine administration should not delay implementation of external pacing for patients with poor perfusion 1, 2
- Excessive doses of atropine (>3 mg) may cause central anticholinergic syndrome, including confusion, agitation, and hallucinations 2
- Dosages of dopamine >20 mcg/kg/min may result in vasoconstriction or arrhythmias 1
- Monitor for potential development of ischemic chest pain with isoproterenol 1