Anaphylaxis and Its Management

Study Notes

Anaphylaxis

Definition: Severe allergic reaction (systemic or generalized) triggered by re-exposure to an allergen.
Pathophysiology:
- Initial exposure: B-lymphocytes produce IgE antibodies. IgE attaches to mast cells and basophils.
- Subsequent exposure: Increased IgE production. IgE binding to mast cells causes degranulation, releasing histamine.
- Effects: Histamine causes vasodilation (reduced blood pressure), bronchoconstriction, and increased vascular permeability (fluid leaks from vessels). Platelet-activating factor and Prostaglandin D2 contribute to these effects, further impacting airway function and blood pressure.
Treatment:
- Call for help: Medical emergency requiring a multidisciplinary team (MDT) response.
- Assessment: Perform a focused assessment (A-to-E).
- Remove trigger: Identify and eliminate the allergen.
- Airway: Potential airway compromise. Secure airway and provide high-flow oxygen (100%). Prepare for intubation.
- Breathing: Monitor respiratory rate (RR). High RR might indicate breathing problems.
- Circulation: Monitor heart rate (HR). High HR, low blood pressure (BP) indicates probable circulatory issues. Administer intramuscular (IM) adrenaline (epinephrine) 0.5mg (500 mcg). Initiate IV fluids (500 mL of 0.9% NaCl).
- Disability: Potential loss of consciousness (shock).
- Exposure: Monitor for rash and swelling. Check for cold extremities (possible shock).
- Repeat adrenaline: If no response after 5 minutes, repeat the IM adrenaline dose. If still no response, consider refractory management (e.g., nebulizers, adrenaline infusion).