108 Immune Disorders – Type I Hypersensitivity Severe Reactions – Anaphylactic Shock

Anaphylactic Shock: Progression from Bad to Worse

1. Definition:
   • Anaphylaxis: Severe, life-threatening systemic hypersensitivity reaction.
2. Mechanism:
   • Triggered by an allergen (e.g., peanuts) in sensitized individuals.
   • Allergen exposure leads to massive histamine release from mast cells with pre-existing IgE.
3. Pathophysiology:
   • Systemic vasodilation and increased capillary permeability.
   • Results in hypotension (low blood pressure) and poor blood flow.
   • Brain is sensitive to low oxygen, leading to symptoms like fainting, confusion, irritability.
4. Symptoms:
   • Gastrointestinal: Nausea, vomiting, diarrhea.
   • Neurological: Weakness, anxiety, dizziness, confusion, fainting.
   • Skin: Itching, hives, contact dermatitis (in localized reactions).
   • Respiratory: Bronchoconstriction, mucus production, dyspnea (shortness of breath), coughing.
   • Cardiovascular: Weak, rapid pulse due to vasodilation and low blood pressure.
5. Complications:
   • Hypoxia: Poor gas exchange due to bronchiole constriction and mucus.
   • Acidosis: Increased lactic acid production due to anaerobic respiration.
   • Potentially fatal if untreated.
6. Common Allergens:
   • Latex, insect stings, nuts, shellfish, penicillin, various drugs.
7. Immediate Treatment:
   • Epinephrine (EpiPen): Causes bronchodilation and vasoconstriction to counteract histamine effects.
   • Emergency response: Call 911, administer CPR if necessary.
   • Positioning: Ensure the person is positioned for optimal breathing.
8. Additional Treatments:
   • Glucocorticoids: Reduce inflammation.
   • Antihistamines: Block histamine receptors.
   • Supplemental oxygen: Provided by ER or paramedics to stabilize oxygen levels.
9. Identification and Avoidance:
   • Identify allergens through skin tests, food diaries, blood tests for specific IgE.
   • Avoid known allergens to prevent reactions.
   • Carry and know how to use an EpiPen.
   • Wear a MedicAlert bracelet.
10. Long-term Management:
    • Allergy shots: Gradual desensitization to allergens.
    • New treatments: FDA-approved peanut allergy pills and patches.
    • Preventative measures: Remove allergens from the environment, use over-the-counter treatments for minor allergies.
11. Key Points:
    • Anaphylactic shock is distinct from common allergic reactions and respiratory infections.
    • It requires immediate medical intervention and ongoing management to prevent recurrence.