What is the treatment for anaphylaxis with bradycardia?

Treatment of Anaphylaxis with Bradycardia

In anaphylaxis with bradycardia, administer atropine 600 μg IV immediately after epinephrine administration to address the bradycardic component while continuing standard anaphylaxis management. 1

Initial Management Algorithm

1. Immediate epinephrine administration

   • Administer epinephrine 0.2-0.5 mg (1 mg/mL) IM into the lateral thigh 1
   • Repeat every 5-15 minutes as needed if symptoms persist
   • Epinephrine is first-line treatment with no absolute contraindications in anaphylaxis 1

2. Specific management for bradycardia

   • Administer atropine 600 μg IV immediately after epinephrine 1
   • Monitor heart rate response

3. Fluid resuscitation

   • Administer normal saline 1-2 L IV infusion at 5-10 mL/kg in first 5 minutes 1
   • Continue with crystalloids or colloids in boluses of 20 mL/kg, followed by slow infusion
   • Large-volume fluid resuscitation is critical as anaphylaxis can cause transfer of up to 35% of intravascular volume into extravascular space 1

4. Antihistamines

   • H1/H2 antagonists: diphenhydramine 50 mg IV plus ranitidine 50 mg IV 1
   • Note that antihistamines should not delay epinephrine administration

Management of Persistent Hypotension

If hypotension persists despite epinephrine and fluid resuscitation:

1. Vasopressors

   • Dopamine: 400 mg in 500 mL, at a rate 2-20 μg/kg/min 1, or
   • Vasopressin: 25 U in 250 mL of 5% DW or NS (0.1 U/mL), dose of 0.01–0.04 U/min 1

2. For patients on beta-blockers

   • Administer glucagon 1-5 mg IV infusion over 5 minutes 1
   • May repeat or follow with infusion of 5-15 μg/minute
   • Glucagon works through non-β-receptor mediated inotropic and chronotropic effects 1

3. Corticosteroids

   • Administer equivalent dose to 1-2 mg/kg of IV methylprednisolone every 6 hours 1
   • Primarily helps prevent biphasic reactions rather than treating acute symptoms 1

Special Considerations for Bradycardia in Anaphylaxis

Bradycardia occurs in approximately 10% of anaphylaxis cases during anesthesia 1. This presentation requires specific attention:

• Bradycardia may indicate severe anaphylaxis or be related to pre-existing conditions
• Patients on β-blockers are at higher risk for bradycardia during anaphylaxis and may be resistant to epinephrine treatment 1
• Atropine should be administered promptly when bradycardia is present 1

Monitoring and Observation

• Continuously monitor vital signs until resolution 1
• For severe reactions, observe for at least 24 hours 1
• Be vigilant for biphasic reactions, which can occur in up to 20% of cases 1

Pitfalls and Caveats

1. Do not delay epinephrine administration

   • Even in patients with cardiovascular disease, the risk of death from untreated anaphylaxis outweighs concerns about epinephrine side effects 1

2. Recognize that bradycardia is atypical but significant

   • While tachycardia is more common in anaphylaxis, bradycardia requires specific intervention with atropine 1

3. Be aware of medication interactions

   • Patients on monoamine oxidase inhibitors or tricyclic antidepressants may have prolonged epinephrine effects 1
   • Beta-blockers can mask typical signs of anaphylaxis and reduce response to epinephrine 1

4. Differentiate from BRASH syndrome

   • While not directly related to anaphylaxis, BRASH syndrome (Bradycardia, Renal failure, AV nodal blockade, Shock, and Hyperkalemia) can present similarly 2, 3
   • BRASH syndrome requires different management focusing on hyperkalemia treatment and improving renal function 3

By following this algorithm and recognizing the unique challenges of anaphylaxis with bradycardia, clinicians can effectively manage this potentially life-threatening condition.