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Allergic Reaction / Anaphylaxis

Category: Medical Sources: raw/protocols/nm-sop-guidelines-treatment-2022.pdf Last updated: 2026-04-03

Overview

Anaphylaxis is a severe, systemic allergic reaction involving multiple organ systems — primarily the airway, respiratory tract, and cardiovascular system. It is a life-threatening emergency requiring immediate epinephrine. Allergic reactions exist on a spectrum from localized (hives, localized swelling) to anaphylaxis (systemic involvement with airway compromise or cardiovascular collapse).

The EMT-B must distinguish between a simple allergic reaction (localized skin findings without systemic involvement) and anaphylaxis (systemic involvement — airway, breathing, or circulation compromised). Epinephrine is only indicated when systemic involvement is present.

Key Points

  • Anaphylaxis triggers: insect stings, food (peanuts, shellfish, tree nuts, dairy), medications (penicillin, NSAIDs), latex, contrast dye, exercise, idiopathic
  • Three system involvement criterion for epinephrine: Respiratory compromise (wheeze, stridor, dyspnea) OR cardiovascular compromise (hypotension, tachycardia, syncope) OR both — localized hives alone do NOT trigger epinephrine
  • "Silent chest" is ominous in anaphylaxis — bronchospasm so severe that no air moves, producing no wheeze
  • Patient may have their own EpiPen — this can be used; document time and dose
  • Epinephrine may need to be repeated; effect is short-lived (15–20 minutes)
  • Even if patient appears to improve with epinephrine, all anaphylaxis patients must be transported — biphasic reactions occur in up to 20% of cases (second wave of symptoms hours later)

Assessment Relevance

History (history-taking): - SAMPLE: Known allergies, allergen exposure (what, when, how much), prior anaphylaxis, prior EpiPen use, medications (antihistamines, steroids taken pre-arrival may blunt presentation), last meal - OPQRST: Onset (typically rapid — minutes after exposure), what provoked it, symptoms

Physical exam (secondary-assessment): - Airway: Stridor (upper airway edema), hoarseness, drooling, difficulty swallowing - Breathing: Wheezing (bronchospasm), decreased/absent breath sounds, SpO2, respiratory rate/effort - Circulation: BP, pulse rate and quality, skin color, capillary refill, diaphoresis - Skin: Urticaria (hives), angioedema (facial/lip/tongue swelling), flushing, pallor - GI: Nausea, vomiting, abdominal cramping (systemic involvement even without respiratory compromise)

Priority indicators: stridor, inability to speak, silent chest, hypotension, loss of consciousness

Procedures

  1. Scene size-up (scene-size-up): identify trigger if visible (bee sting site, food container); remove stinger by scraping (not pinching)
  2. Primary assessment (primary-assessment): assess airway (stridor?), breathing (wheeze, SpO2), circulation (BP, pulse)
  3. Determine: localized reaction vs. systemic anaphylaxis
  4. If systemic involvement (airway compromise, respiratory distress, or cardiovascular collapse):
  5. Administer epinephrine IM — see epinephrine-auto-injector
  6. Apply high-flow oxygen via NRB mask — see oxygen-administration
  7. Request ALS intercept immediately
  8. Position: supine with legs elevated if hypotensive; sitting upright if respiratory distress
  9. Transport — do not delay for reassessment
  10. Reassess (reassessment) every 5 minutes; may need to repeat epinephrine
  11. Monitor for biphasic reaction

NM Protocol Notes

From NM EMS Treatment Guidelines (2022):

EMT-B and First Responder scope: - EPINEPHRINE 1:1,000 (1 mg/mL) — IM, lateral thigh - Adult: 0.3 mg IM using pre-measured pre-filled device (EpiPen) or 0.3 mL dose-limiting syringe - Pediatric: 0.01 mg/kg IM using pre-measured pre-filled pediatric device; not to exceed adult dose - May be repeated every 5–15 minutes if signs of anaphylaxis and hypoperfusion persist - Cardiac monitoring required at all levels for all patients receiving epinephrine - For insect bites: remove stinger with scraping motion; do not pinch the stinger with tweezers

Additional ALS medications (not EMT-B scope — for context/ALS intercept): - ALBUTEROL 5.0 mg nebulized (or Duo Neb 2.5mg Albuterol + 0.5mg Ipratropium) or LEVALBUTEROL 0.63–1.25 mg — for bronchospasm - IPRATROPIUM 0.5 mg — adjunct bronchodilator - Large bore IV/IO isotonic solution — titrate to maintain adequate perfusion - DIPHENHYDRAMINE (Benadryl): - Adult: 25–50 mg slow IV/IO at 1 mL/min or deep IM - Pediatric: 1 mg/kg slow IV/IO or deep IM (max 50 mg) - SOLUMEDROL (methylprednisolone): Adult 125 mg IV/IO; Pediatric 1–2 mg/kg IV/IO (max 125 mg) OR DEXAMETHASONE: Adult 10 mg IV/IO/IM; Pediatric 0.6 mg/kg (max 10 mg) - For cardiovascular collapse with hypotension (paramedic only): IV epinephrine drip; EPINEPHRINE 1:10,000 mini-bolus

Epinephrine IV drip

Concept Link

Anaphylaxis causes distributive shock — the same mechanism covered in shock-physiology. The vasodilation and maldistribution of blood flow described there explains why epinephrine works: it reverses vasodilation (alpha-1) and supports cardiac output (beta-1/beta-2). (paramedic only): Consider 0.5 mcg/kg/min when cardiovascular collapse present despite repeated IM epinephrine doses + at least 60 mL/kg IV fluid boluses

NREMT Relevance

Common NREMT question angles: - The three criteria for epinephrine: systemic involvement (airway, breathing, or cardiovascular) — localized hives alone are NOT sufficient - EpiPen sites: lateral thigh (preferred), outer thigh — can administer through clothing - Epinephrine 1:1,000 vs. 1:10,000 — the auto-injector contains 1:1,000 (IM use); 1:10,000 is IV use (ALS) - Adult dose 0.3 mg, pediatric dose 0.15 mg (EpiPen Jr) or 0.01 mg/kg - All anaphylaxis patients must be transported (biphasic reaction risk) - Stinger removal: scraping not pinching

Sources

  • raw/protocols/nm-sop-guidelines-treatment-2022.pdf — Allergic Reaction/Anaphylaxis protocol (p. 33–34)