Anaphylaxis (Table 10) is a Type I hypersensitivity reaction. Initial exposure to an allergen results in antigen-specific antibody production dominated by the immunoglobulin E (IgE) isotype. Following re-exposure, IgE antibodies bind to mast cells and basophils associated with mucosal and epithelial tissues. The simultaneous binding of an antigen to adjacent IgE molecules fixed to Fc receptors triggers degranulation of mast cells and basophils resulting in the release of histamine, leukotrienes, prostaglandins, chemokines, enzymes and cytokines in target tissues.
Prevention:- Identify at-risk patient
- A negative history of prior anaphylactic reaction does not rule out the possibility of a type I allergic reaction
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Signs and symptoms:- 1 to 15 minutes following exposure to a specific allergen
- Pruritus, urticaria, angioedema
- Coughing, stridor, dyspnea, wheezing
- Agitation, flushing, palpitation
- Unresponsiveness, convulsion
- Hypotension, cardiogenic shock
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Emergency response:- Place patient in a supine position
- Select an auto-injector (≥30 kg: 0.3 mg)
- Remove the auto-injector from its protective case
- Check the expiration date
- Confirm liquid is clear and not discolored
- Grasp the auto-injector in dominant hand; remove the safety cap
- Hold the patient’s leg steady
- Place (jab) at right angle against the outer thigh
- Can go through clothing
- Press firmly to inject
- Keep in place for ≈5 seconds
- Small amount of liquid remaining is normal
- Remove and massage site for 10 seconds
- Check if needle retracted or needs re-casing
- Immediately Call 911
- Inform dispatcher about epinephrine administration
- Repeat injection in 15-20 min if necessary
- Max 2 doses without medical supervision
- Do not discard injector (hand over to EMS)
- Patients with stridor/wheezing: O₂ (4-6 L/min)
- Monitor vital signs
- If unresponsive/no pulse: Start CPR/defibrillation
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Nota bene:- Signs of recovering: normal respiration/vital signs
- Signs of deterioration: loss of consciousness, unstable vitals
- Special cases (CV disease/Diabetes): smaller doses
- Beta-blocker patients may require MORE epinephrine
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