Anaphylaxis



Anaphylaxis


Kristina Wilson, MD, MPH, FAAP, CAQSM



BASICS



  • The causative agent in anaphylaxis remains unknown in up to 1/3 of cases.


  • Food is the most common causative agent (about 1/3 of known cases) in children.


  • Pharmacotherapeutic agents are the most common cause in adults.


  • Other common causes include Hymenoptera stings and latex.


  • Key to management and treatment is early recognition and immediate initiation of appropriate medical therapy.


  • Epinephrine is the undisputed initial therapy for anaphylaxis, and its administration should never be delayed.


  • Failure to inject epinephrine promptly has been identified as the most important factor contributing to death in patients experiencing anaphylaxis.


DESCRIPTION



  • Severe, potentially life-threatening systemic hypersensitivity reaction


  • Allergic type mediated by immunoglobulin E (IgE):



    • Involves the respiratory and/or cardiovascular systems


    • Patients may have a history of less severe reaction previously on exposure to relevant allergen.


  • Exercise-induced anaphylaxis (EIAn):



    • Occurs in response to physical exertion


    • Subset of patients must have associated food trigger—food-dependent exercise-induced anaphylaxis (FDEIAn).


  • Cold urticaria:



    • Reproducible, rapid onset of erythema, pruritus, and edema after exposure to cold


    • Most idiopathic


    • Occasionally involves abnormal circulating proteins (i.e., cryoglobulins or cryofibrinogens); agglutinates or precipitates at lower temperatures


EPIDEMIOLOGY

Death rates from the most common causes of anaphylaxis have varied:



  • Food induced has increased.


  • Insect sting has declined.


  • Drug induced has increased.


Incidence



  • 8 to 50/100,000 person-years in Western countries


  • Incidence rates vary widely owing to differences in sample populations, data-collection methods, and varying definitions of anaphylaxis.


Prevalence

Lifetime prevalence of 0.05-2.0% in Western countries (1), rising especially in children


ETIOLOGY AND PATHOPHYSIOLOGY



  • Allergic: IgE-mediated:



    • Drugs


    • Venom


    • Latex


    • Vaccines


    • Food


  • Nonallergic: direct basophil/mast cell-mediated:



    • Radiocontrast dye


    • Opioid drugs


RISK FACTORS



  • Prior anaphylaxis event can predict subsequent anaphylaxis:



    • As the only risk factor, prior anaphylaxis has a poor ability to identify patients who might develop anaphylaxis.


    • 14% of anaphylaxis admissions for peanut sensitivity have a prior history of anaphylaxis.


  • Often occurs following a previous mild allergic reaction to the same allergen


  • Most proposed risk factors have limited value owing to a low specificity:



    • Coexisting atopic disease; especially poorly controlled asthma


    • Older age at first reaction to food allergy


  • Clinical risk factors for fatality in anaphylactic reactions (2):



    • Severe or uncontrolled asthma


    • Cardiovascular disease


    • Mastocytosis




Mar 14, 2020 | Posted by in SPORT MEDICINE | Comments Off on Anaphylaxis
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