Should atropine or epinephrine be given to a patient with bradycardia (Heart Rate (HR) of 45) who is actively vomiting and being intubated?

Management of Bradycardia During Emergency Intubation in an Actively Vomiting Patient

Atropine should be administered immediately for this patient with symptomatic bradycardia (HR 45) during emergency intubation, not epinephrine. 1, 2

Initial Treatment Algorithm

First-Line: Atropine Administration

• Administer atropine 0.5-1 mg IV immediately, repeating every 3-5 minutes as needed up to a maximum total dose of 3 mg 1, 2
• Atropine is the first-line drug for acute symptomatic bradycardia and is particularly effective when bradycardia occurs during laryngoscopy and intubation due to vagal stimulation 1, 2
• The peak action of atropine occurs within 3 minutes of IV administration 1
• Avoid doses less than 0.5 mg, as paradoxically this may cause further slowing of heart rate through central reflex vagal stimulation 1, 2

Critical Context: Vagal Stimulation During Intubation

• Bradycardia during emergency intubation commonly results from vagal response to laryngoscopy, hypoxia/ischemia, or as a reflex response to positive pressure ventilation 1
• Active vomiting further increases vagal tone, making atropine particularly appropriate as it directly antagonizes this parasympathetic stimulation 1, 3
• Atropine reduces vagal tone, enhances sinus node discharge rate, and facilitates AV conduction through its parasympatholytic (anticholinergic) activity 1, 3

When to Escalate to Epinephrine

Second-Line Treatment

• Epinephrine is reserved for bradycardia that fails to respond to atropine, with a starting dose of 2-10 mcg/min IV infusion 1, 2
• Alternative second-line agents include dopamine 2-10 mcg/kg/min IV infusion 1, 2
• Transcutaneous pacing should be considered simultaneously if atropine fails and the patient remains hemodynamically unstable 1, 2

Why Not Epinephrine First

• Epinephrine is not indicated as first-line therapy for bradycardia with a pulse and should only be used after atropine has failed 1, 2
• In the context of vagally-mediated bradycardia during intubation, atropine directly addresses the underlying mechanism, whereas epinephrine provides non-specific chronotropic support 1, 2
• Approximately 50% of patients with symptomatic bradycardia respond to atropine alone, making it the appropriate initial choice 4

Special Considerations and Pitfalls

Aspiration Risk Management

• The actively vomiting patient requires immediate airway protection, but atropine administration should not delay intubation 1
• Atropine is frequently given as an adjunct to reduce nausea and vomiting, which may provide additional benefit in this scenario 1
• Early endotracheal intubation is recommended for life-threatening situations, and atropine can be administered during the intubation process 1

When Atropine May Be Less Effective

• Atropine is likely ineffective in type II second-degree AV block, third-degree AV block with new wide-QRS complex, or infranodal blocks where the conduction problem is below the AV node 1, 2, 5
• However, in the context of intubation-related bradycardia in a previously stable patient, the mechanism is almost certainly vagal stimulation, making atropine highly appropriate 1, 2
• One case report documented paradoxical worsening to ventricular standstill following atropine in a patient with 2:1 heart block, but this is rare and related to infranodal block location 5

Monitoring Response

• Evaluate heart rate response within 3 minutes of atropine administration 1
• If heart rate remains below 50-60 bpm or hemodynamic instability persists after full-dose atropine (3 mg total), immediately prepare for transcutaneous pacing and epinephrine infusion 1, 2
• Continue cardiac monitoring and blood pressure assessment throughout resuscitation 2

Critical Warnings

Dosing Errors to Avoid

• Never administer atropine doses less than 0.5 mg IV, as this may paradoxically worsen bradycardia 1, 2
• Do not exceed 3 mg total dose of atropine, as higher doses may cause central anticholinergic syndrome including confusion, agitation, and hallucinations 1, 2
• Atropine administration should not delay implementation of external pacing if the patient has poor perfusion 1, 2

Contraindications and Cautions

• Use atropine cautiously if acute coronary ischemia or MI is suspected, as increased heart rate may worsen ischemia or increase infarction size 1, 2
• In heart transplant patients, atropine may cause paradoxical high-degree AV block due to lack of vagal innervation, but this is not relevant in this clinical scenario 1, 2