- Biphasic anaphylaxis: recurrence of symptoms within 72 hours without re‑exposure
- Refractory anaphylaxis: persistent symptoms despite 2+ doses of epinephrine
- Cardiovascular collapse: distributive shock unresponsive to fluids and epinephrine
Anaphylaxis
Must-Not-Miss / Red Flags
Patient Explanation
“You’re having a severe allergic reaction that is affecting your whole body. We’ll give you epinephrine immediately to stop the reaction and keep you safe.”
Board Fact
“Epinephrine is the first‑line and most important treatment for anaphylaxis – there are no absolute contraindications in this setting.”
ICD-10
T78.2XXA
Definition & Core Concept
Anaphylaxis is a severe, life‑threatening systemic hypersensitivity reaction characterized by rapid onset of airway, breathing, or circulatory compromise, usually with skin and mucosal changes.
Epidemiology & Risk Factors
- Lifetime prevalence: 0.5‑2% in the general population
- Most common triggers: food (peanuts, tree nuts, shellfish), medications (antibiotics, NSAIDs), insect stings
- Risk factors: previous anaphylaxis, asthma, mast cell disorders
Clinical Vignette
A 25‑year‑old woman develops urticaria, facial swelling, and difficulty breathing 15 minutes after eating shrimp. She has a history of shellfish allergy. BP is 85/50, HR 120, with audible wheezing.
Pearls & Pitfalls
- Epinephrine is most effective when given early – do not delay for IV access or steroids.
- Patients taking beta‑blockers may have refractory anaphylaxis; glucagon can be considered as adjunct therapy.
Discharge & Follow-Up
Prescribe 2 epinephrine auto‑injectors. Refer to allergy/immunology for skin testing. Provide anaphylaxis action plan and medical alert bracelet.
Literature & Guidelines
WAO 2024 Anaphylaxis Guidelines. PMID: 38584210.