Emergency
Anaphylaxis — the essentials
Anaphylaxis is a rapidly evolving, multi-system, life-threatening allergic reaction. It is the archetypal take-action emergency: the diagnosis is clinical, the window is minutes, and the one intervention that changes mortality — prompt intramuscular epinephrine to the mid-outer thigh — sits within the RN’s standing-order scope.
Recognize it (clinical diagnosis)
- Skin/mucosa (urticaria, flushing, lip/tongue swelling) PLUS airway, breathing, or circulation involvement after likely exposure
- OR sudden hypotension / airway compromise after a known allergen — may lack skin signs
- Onset usually minutes to ~2 hours after a trigger (food, sting, drug, contrast)
- Do not wait for labs (tryptase) to act — treat clinically
First action: IM epinephrine
- Drug & concentration
- Epinephrine 1 mg/mL (1:1000), IM
- Dose (adult)
- 0.01 mg/kg up to 0.5 mg (autoinjector delivers 0.3 mg)
- Site
- Mid-outer (vastus lateralis) thigh
- Repeat
- Every 5–15 minutes as needed
- Never
- The 1 mg/mL IM dose is NEVER given IV push
Priority nursing actions
- Give IM epinephrine FIRST — before antihistamines or steroids
- Position supine with legs elevated; call for help
- High-flow oxygen; prepare for provider-ordered IV fluid bolus if hypotensive
- Reassess and repeat epinephrine as needed; monitor for biphasic reaction
Common NGN / NCLEX traps
- Giving an antihistamine (diphenhydramine) first — it does not treat airway or shock
- Reaching for albuterol or hydrocortisone before epinephrine
- Sitting the hypotensive patient upright — keep supine, legs elevated
- Assuming steroids prevent biphasic reactions — not recommended for that purpose
For practicing nurses
What’s changed (if you trained a while ago)
- Antihistamines and corticosteroids are NOT recommended to prevent biphasic reactions — the 2023 parameter advises against routine use for that purpose.
- Observation is risk-stratified, not a fixed "watch 4 hours" rule; biphasic reactions can recur up to ~72 hours (typically 1–12 h).
- Severe anaphylaxis can occur WITHOUT skin signs — a known allergen plus isolated hypotension or airway compromise is enough to act.
- Patients typically go home with two auto-injectors and timed serum tryptase may be drawn (ASAP + within 1–2 h).
On the floor (practical pearls)
- Concentration safety is the classic error: 1 mg/mL (1:1000) is IM only and NEVER IV push; the IV/infusion form is 0.1 mg/mL.
- Don’t sit the hypotensive patient up — sudden upright posture can precipitate collapse; keep supine, legs elevated.
- Epinephrine before everything: antihistamines and steroids do not treat airway or shock and must not delay it.
- Reassess and be ready to repeat epinephrine every 5–15 minutes; set up for a provider-ordered IV fluid bolus if hypotensive.
- Teach auto-injector technique and the biphasic-recurrence warning before discharge — it’s a high-yield CE teaching moment.
Key references
- Anaphylaxis: A 2023 Practice Parameter Update, AAAAI/ACAAI Joint Task Force, 2023
- World Allergy Organization Anaphylaxis Guidance, WAO, 2020
- Davis's Drug Guide for Nurses — Epinephrine monograph, F.A. Davis, 2023
- Lewis's / Brunner & Suddarth's Medical-Surgical Nursing — Anaphylactic shock, 2022–2024
- NICE — Anaphylaxis: assessment and referral after emergency treatment, NICE, 2026
Sources: Based on the 2023 AAAAI/ACAAI Practice Parameter, WAO (2020/2026), and Davis’s Drug Guide.
