Anaphylactic Shock: Progression of Allergy Symptoms 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:

Symptoms are dependent on location of allergen in the body.  Allergen binds to IgE receptors on Mast Cells and Basophils, both of which are WBCs that will then stimulate the Inflammatory Response by degranulating, releasing vasodilators histamine, prostaglandins, leukotrienes, bradykinins.  Ingested allergens will stimulate gastrointestinal signs and symptoms (e.g., nausea, vomiting, diarrhea) as well as systemic signs and symptoms as the ingested allergen is absorbed by intestinal blood vessels and is then spread throughout the body.  Ingested allergens can therefore also give rise to itching, hives, bronchoconstriction, bronchiole swelling, dyspnea, hypotension, weakness, anxiety, dizziness, and loss of consciousness.

• • 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:

• • Insect stings, nuts, shellfish, strawberries, latex, 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 (e.g., hay-fever) and respiratory infections (cold, flu).
  • It requires immediate medical intervention and ongoing management to prevent recurrence.