Anaphylaxis


Epidemiology

Definitions

  • Anaphylactoid Reaction
    • Mechanism Involves Direct Mast Cell Activation (Importantly without Prior Sensitization)
    • However, Anaphylactoid Reaction is Clinically Indistinguishable from Anaphylaxis
  • Anaphylaxis
    • Mechanism Involves IgE-Mediated Mast Cell Activation (Type I Hypersensitivity Reaction)

Specific Subset of Allergens Account for 90% of Anaphylaxis Cases

  • Egg
  • Fish/Shellfish
  • Milk
  • Soy
  • Peanuts
  • Tree Nuts
  • Wheat

Risk Factors for Severe/Fatal Anaphylaxis

  • Age-Related Factors
    • Infant: inability to describe symptoms
    • Adolescent/Young Adult: increased risk-taking behaviors that may impede ability to obtain prompt medical care, etc
    • Labor/Delivery: increased risk from medications
    • Elderly: increased risk of fatality from medication or venom-associated anaphylaxis
  • Concomitant Disease-Related Factors
  • Concomitant Medications/Toxins-Related Factors
    • Angiotensin Converting Enzyme (ACE) Inhibitors (see Angiotensin Converting Enzyme Inhibitors)
    • Antidepressants: use may impair the ability to recognize anaphylaxis triggers and symptoms
    • β-Blockers (see β-Adrenergic Receptor Antagonists)
    • Ethanol (see Ethanol): use may impair the ability to recognize anaphylaxis triggers and symptoms
    • Recreational Drugs: use may impair the ability to recognize anaphylaxis triggers and symptoms
    • Sedatives: use may impair the ability to recognize anaphylaxis triggers and symptoms
  • Presence of Physiologic Defect in Mediator Degradation Pathways
    • Low Serum ACE Activity: impaired ability to degrade tryptase, histamine, bradykinin
    • Low Serum PAF Acetylhydrolase Activity: impaired ability to degrade platelet-activating factor

Risk Factors Which Amplify Anaphylaxis

  • Acute Infection
  • Disruption of Routine
    • Travel
  • Emotional Stress
  • Exercise: best characterized amplifying factor
    • Commonly Associated with Anaphylaxis Due to Concomitant Ingestion of a Specific Food Trigger
      • Celery
      • Omega-5 Gliadin
      • Shellfish
      • Wheat
    • Less Commonly Associated with Anaphylaxis Due to Concomitant Ingestion of Ethanol or NSAID Drug: these enhance intestinal permeability and allergen absorption
  • Premenstrual Status

Etiology

IgE-Mediated Mast Cell Activation (Type I Hypersensitivity) (see Immune Hypersensitivity)

Foods/Food Additives (see Food Allergy)

Stings/Bites/Envenomations

Drugs

Other

Immunologic Non-IgE-Mediated Mast Cell Activation

Non-Immunologic Direct Mast Cell/Basophil Activation

Other


Physiology

Molecular Mechanism of Anaphylaxis

Distributive Shock (Similar to Sepsis) (see Hypotension)


Diagnosis

Mast Cell Serum Tryptase Level (see Serum Tryptase)

RAST Testing

Chest X-Ray (CXR) (see Chest X-Ray)


Diagnostic Criteria (One of Three Following Criteria) (J Allergy Clin Immunol, 2006) [MEDLINE]

Acute Onset of Illness (Within Min-Several Hours) with Skin/Mucosal Tissue Involvement (Flushing/Generalized Erythema, Hives, Pruritus, Swollen Lips/Tongue/Uvula) and At Least One of the Following

Two or More of the Following Occurring Rapidly After Exposure to a Likely Antigen

Hypotension After Exposure to a Known Allergen for a Specific Patient Within Min-Several Hours (see Hypotension)


Clinical Manifestations

General Comments

Cardiovascular Manifestations

Dermatologic Manifestations

Gastrointestinal Manifestations

Neurologic Manifestations

Otolaryngologic Manifestations

Pulmonary Manifestations

Other Manifestations


Anaphylactoid Reactions to Contrast Medium

Cutaneous and Mucosal

Smooth Muscle

Types of Contrast Reactions

Minor

Major


Treatment

General Treatment

Epinephrine (see Epinephrine)

Preloaded Epinephrine Injectable Devices

Corticosteroids (see Corticosteroids)

H1-Histamine Receptor Antagonists (see (see H1-Histamine Receptor Antagonists)

H2-Histamine Receptor Antagonists (see H2-Histamine Receptor Antagonists)


References