Anaphylaxis is a life-threatening allergic reaction that requires immediate recognition and treatment to prevent airway compromise, circulatory collapse, and death.
🛑 Step-by-Step Anaphylaxis Algorithm
1️⃣ Recognize Anaphylaxis
Anaphylaxis is a rapid-onset, systemic allergic reaction involving:
- Airway – Swelling, stridor, difficulty breathing.
- Breathing – Wheezing, bronchospasm, hypoxia.
- Circulation – Hypotension, tachycardia, shock.
- Skin – Urticaria (hives), angioedema, flushing.
- GI – Nausea, vomiting, abdominal pain.
📌 Clue: Symptoms typically appear minutes after exposure to an allergen (e.g., drugs, food, latex, insect stings).
2️⃣ Immediate Treatment – Epinephrine is First-Line
- 💉 Give IM Epinephrine ASAP (DO NOT delay!)
- Dose: 0.3–0.5 mg IM (1:1000 concentration) every 5–15 min as needed
- Site: Mid-thigh (vastus lateralis)
- Mechanism:
- Alpha-1, beta-1, and beta-2 agonist.
- Reverses vasodilation (alpha-1), increases BP (alpha-1), and bronchodilates (beta-2).
📌 Never substitute antihistamines or steroids for epinephrine!
3️⃣ ABCs – Airway, Breathing, Circulation
- Secure the airway early if signs of swelling/obstruction (e.g., stridor, hoarseness, swelling).
- High-flow oxygen (100%) if respiratory distress or hypoxia.
- Start IV fluids (Rapid bolus 1-2 L normal saline for hypotension).
4️⃣ Adjunctive Medications (Supportive Therapy)
- H1 Antihistamine (Diphenhydramine 25–50 mg IV/IM) – For hives/itching.
- H2 Antihistamine (Ranitidine/Famotidine IV) – Helps reduce histamine effects.
- Corticosteroids (Methylprednisolone 125 mg IV or Hydrocortisone 200 mg IV) – Prevents biphasic reaction, but does not work immediately.
- Beta-agonist (Albuterol Nebulizer) – For bronchospasm/wheezing.
📌 Steroids and antihistamines are NOT first-line and should never delay epinephrine!
5️⃣ Refractory Anaphylaxis (Not Responding to IM Epinephrine)
If the patient remains hypotensive or deteriorates despite IM epinephrine:
- Start Epinephrine Infusion (IV)
- Mix 1 mg epinephrine in 1L NS → Start at 1-4 mcg/min, titrate as needed.
- Consider Vasopressors (Norepinephrine, Vasopressin)
- For persistent shock despite fluids & epinephrine.
📌 If patient is on a beta-blocker and resistant to epinephrine → Give Glucagon (1-2 mg IV q5min PRN).
6️⃣ Monitor & Observe
- Mild cases: Observe for 4–6 hours.
- Severe cases (hypotension, airway involvement): Admit to ICU for at least 24 hours due to risk of biphasic anaphylaxis.