Why it matters
When you see a patient with a rash and low blood pressure, you’re looking at a life-threatening emergency until proven otherwise. Anaphylaxis is a clinical diagnosis, and delay in giving epinephrine kills. Rookies often hesitate, waiting for labs or second opinions — but here, seconds matter.
1) The 30-second story
- Sudden onset after exposure (food, insect sting, drug, latex).
- Rash (urticaria, flushing, angioedema) + airway, breathing, or circulation involvement.
- Hypotension, wheeze, stridor, GI symptoms (vomiting, cramping) all point to systemic reaction.
2) Quick differential
- Anaphylaxis (most common and deadly).
- Sepsis (rash in meningococcemia, toxic shock).
- Drug reaction (SJS/TEN, DRESS — usually slower onset).
- Other shock states (cardiogenic, distributive, hypovolemic).
3) Red flags 🚨
- Hypotension after allergen exposure.
- Airway involvement (tongue/lip swelling, stridor).
- Wheeze/resp distress.
- Rapid progression of symptoms.
- Previous anaphylaxis history.
4) Bedside exam & first steps
- Airway: stridor, voice change, tongue swelling → intubation may be needed early.
- Breathing: wheezing, hypoxia.
- Circulation: hypotension, tachycardia, weak pulses.
- Skin: urticaria, flushing, angioedema (may be absent in 10–20% of cases).
- Neuro: altered sensorium from shock.
5) Investigations
Diagnosis is clinical — do not delay treatment.
- If time allows after stabilization: CBC, BMP, tryptase (not routine ED).
- CXR/ECG if considering mimics.
- Point-of-care glucose/lactate in unstable patients.
6) Management in the ED
Epinephrine is first, second, and third line.
- IM epinephrine 0.3–0.5 mg (1:1000) into mid-anterolateral thigh.
- Repeat every 5–15 min if symptoms persist.
- Place patient supine (unless respiratory distress prevents).
- High-flow O₂, IV fluids (large bore, rapid crystalloids for hypotension).
- Adjuncts (after epi, never before):
- Antihistamines (H1 + H2 blockers) for cutaneous symptoms.
- Corticosteroids (prednisone, methylprednisolone) to reduce biphasic risk (not acute lifesaving).
- Beta-agonist nebulizers for bronchospasm.
If refractory hypotension:
- IV epinephrine infusion (cautiously, with monitoring).
- Consider glucagon in patients on beta-blockers.
Airway compromise:
- Early intubation if progressive swelling/stridor.
- Surgical airway as last resort.
7) Disposition
- Admit/observe: all anaphylaxis patients should be observed for 4–6h minimum (longer if severe, biphasic risk).
- Discharge criteria: resolution of symptoms, stable vitals, no progression, reliable follow-up.
- On discharge:
- Prescribe epinephrine auto-injector.
- Clear instructions on allergen avoidance.
- Referral to allergy/immunology.
- Educate patient: “If symptoms return, use epi immediately, then call EMS.”
Rookie pearls
- Give epi IM immediately — don’t wait for IV, don’t wait for the attending.
- Skin findings may be absent — hypotension + exposure = anaphylaxis until proven otherwise.
- Patients on beta-blockers may not respond well — think glucagon.
- Do not send home after “just a little rash and low BP” — always observe.
- Always prescribe an auto-injector on discharge.
Common pitfalls
- Delaying epinephrine while giving antihistamines/steroids.
- Using IV push epi inappropriately (risk of arrhythmias).
- Forgetting airway assessment early — losing the airway in anaphylaxis is catastrophic.
- Discharging too early without observation.
- Not educating patients about biphasic reactions.
Leave a Reply