Anaphylaxis Management and Diagnosis

Definition and Pathophysiology

Anaphylaxis is an acute, life-threatening systemic allergic reaction resulting from sudden release of mediators from mast cells and basophils, with IgE-mediated and non-IgE-mediated mechanisms producing identical clinical presentations 1, 2
A characteristic feature of anaphylaxis is increased vascular permeability, allowing transfer of up to 50% of intravascular fluid into the extravascular space within 10 minutes, resulting in rapid hemodynamic collapse with minimal or absent cutaneous/respiratory manifestations 1, 2, 6

The more rapidly anaphylaxis develops after exposure, the more likely the reaction is severe and potentially life-threatening 1, 2, 6
Cutaneous manifestations may be delayed or absent in rapidly progressive anaphylaxis, particularly with cardiovascular collapse 1, 2
Diffuse erythema, pruritus, urticaria, and/or angioedema are common cutaneous manifestations 2, 6

Anaphylaxis is a clinical diagnosis that must be made rapidly; confirmatory testing has poor sensitivity and should never delay treatment 3
The NIAID criteria (2006) provide a framework with 95% sensitivity and 71% specificity in emergency settings, though fulfilling criteria is NOT a prerequisite for epinephrine administration 3

Epinephrine is the first-line, life-saving drug for anaphylaxis and should be administered promptly at the onset of apparent anaphylaxis; when in doubt, it is better to give epinephrine 5, 3, 6
The dose of epinephrine is 0.2-0.5 mL intramuscularly (0.01 mg/kg in children, maximum 0.3 mg) 6
Repeat epinephrine every 5 minutes as necessary to control symptoms and increase blood pressure 6

All patients who experience anaphylaxis require comprehensive follow-up care 3
Essential components of post-acute management include education on anaphylaxis and risk of recurrence, trigger avoidance counseling, prescription of epinephrine auto-injector, and referral to allergist-immunologist 5, 3, 7