What are the ACLS (Advanced Cardiovascular Life Support) dosing recommendations for an adult patient with symptomatic bradycardia?

ACLS Dosing for Symptomatic Bradycardia

First-Line Treatment: Atropine

Administer atropine 0.5-1 mg IV as the initial treatment for symptomatic bradycardia, repeating every 3-5 minutes as needed up to a maximum total dose of 3 mg. 1, 2, 3

• Doses less than 0.5 mg should be avoided as they may paradoxically worsen bradycardia through central vagal stimulation 1, 3
• Atropine is most effective for sinus bradycardia, AV nodal block, and sinus arrest 1, 2
• Atropine is likely ineffective for Mobitz type II second-degree AV block or third-degree AV block with wide QRS complex, where the block is infranodal 1, 2, 4

Second-Line Treatment: Vasopressors/Inotropes

If atropine fails to resolve symptomatic bradycardia, initiate dopamine 5-10 mcg/kg/min IV infusion OR epinephrine 2-10 mcg/min IV infusion, titrating to hemodynamic response. 5, 1, 3

Dopamine Dosing

• Start at 5 mcg/kg/min and increase by 5 mcg/kg/min every 2 minutes based on heart rate and blood pressure response 1, 6
• Therapeutic range is 2-10 mcg/kg/min for chronotropic effect 5, 1
• Do not exceed 20 mcg/kg/min as higher doses cause excessive vasoconstriction and arrhythmias 1, 6
• At 5-20 mcg/kg/min, dopamine provides both chronotropic and inotropic effects through beta-1 adrenergic stimulation 1

Epinephrine Dosing

• Administer as continuous IV infusion at 2-10 mcg/min, titrating to desired heart rate and blood pressure 5, 1, 3
• Epinephrine has stronger alpha-adrenergic effects causing more profound vasoconstriction than dopamine 1
• Preferred over dopamine in severe hypotension requiring both strong chronotropic and inotropic support 1

Third-Line Treatment: Transcutaneous Pacing

Initiate transcutaneous pacing immediately for unstable patients who remain hemodynamically compromised despite atropine administration. 1, 2, 3

• Transcutaneous pacing is a Class IIa recommendation for unstable bradycardia unresponsive to atropine 5, 2
• Pacing serves as a temporizing measure while preparing for transvenous pacing if needed 1, 2
• May require sedation/analgesia due to pain in conscious patients 1

Critical Clinical Pitfalls

Atropine-Specific Warnings

• Avoid atropine in heart transplant patients without autonomic reinnervation, as it may cause paradoxical high-degree AV block or sinus arrest 1, 2, 3
• Use cautiously in acute coronary ischemia or MI, as increased heart rate may worsen ischemia or increase infarct size 5, 1, 2
• In patients with infranodal AV block (Mobitz II or third-degree with wide QRS), atropine may precipitate ventricular standstill 1, 4

Vasopressor Warnings

• Use epinephrine with extreme caution in acute coronary ischemia, as it may worsen ischemia 1
• Dopamine doses exceeding 20 mcg/kg/min cause profound vasoconstriction and proarrhythmias 1, 6

Timing Considerations

• Do not delay transcutaneous pacing while giving additional atropine doses in unstable patients 1, 2
• Atropine administration should not delay implementation of external pacing for patients with poor perfusion 1

Special Clinical Scenarios

Post-Spinal Cord Injury

• Consider aminophylline or theophylline for bradycardia refractory to atropine in spinal cord injury patients 5, 2
• Theophylline 100-200 mg slow IV injection (maximum 250 mg) may be effective 5

Post-Cardiac Transplant

• Epinephrine is the preferred agent over atropine in heart transplant patients 1
• Theophylline may restore sinus rate and reduce pacemaker need in post-transplant bradycardia 2

Inferior Myocardial Infarction

• Limit total atropine dose to 0.03-0.04 mg/kg in patients with coronary artery disease 1
• Consider aminophylline for second or third-degree AV block complicating inferior MI 3