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IResuscitation and critical careChapter 12

Anaphylaxis

Anaphylaxis kills by airway oedema, bronchospasm and distributive shock — sometimes all three in the same patient. Intramuscular adrenaline into the anterolateral thigh is the only intervention proven to reduce mortality; everything else is adjunctive.

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On this page01 · Recognising anaphylaxis — when to commit

01 · Recognising anaphylaxis — when to commit
02 · First-line treatment — adrenaline IM
03 · What NOT to lead with — common errors
04 · Refractory anaphylaxis — when 2 IM doses are not enough
05 · Observation, biphasic risk and discharge
Key takeaways
References
Test yourself

Recognising anaphylaxis — when to commit

Anaphylaxis is highly likely when any one of three clinical patterns is present. Do not wait for hypotension — skin plus airway, or skin plus breathing, is enough.

Bedside key actions

UpdatedWhat's new (2024-2026 update)

ERC 2025 + RC UK 2025 explicitly advise against routine corticosteroids — strengthens prior 2021 position
Refractory anaphylaxis: ECPR is now an option in centres where available (ERC 2025 Special Circumstances)

Diagnostic criteria

Criterion 1

Sudden skin/mucosal involvement (urticaria, flushing, lip-tongue swelling) PLUS sudden airway compromise (stridor, hoarseness), respiratory compromise (wheeze, SpO2 < 92%), or hypotension/end-organ dysfunction.

Criterion 2

After exposure to a likely allergen, ≥2 of: skin/mucosa, respiratory, cardiovascular (BP drop, syncope), persistent GI symptoms (cramping vomiting).

Criterion 3

After exposure to a known allergen for that patient — isolated hypotension qualifies. SBP < 90 mmHg in adults, or > 30% drop from baseline.

Pitfalls

Watch out

Up to 20% have NO skin signs — bronchospasm or hypotension after a sting, drug or food in a previously well patient is anaphylaxis until proven otherwise.

Indian-ED note

Common triggers: peanut, tree nut, egg, milk, drugs (penicillin, NSAIDs, IV contrast, neuromuscular blockers), Hymenoptera stings, latex. Also consider Type I hypersensitivity reactions to snake antivenom and food-dependent exercise-induced anaphylaxis (wheat).

First-line treatment — adrenaline IM

Five things, in this order. Adrenaline IM is the only drug that changes mortality. Antihistamines and steroids are adjuncts — they do not treat the airway or shock.

Bedside key actions

Adrenaline

Adrenaline dose — adult

0.5 mg (0.5 mL of 1:1000) IM into the anterolateral mid-thigh. Use a 21G/23G 25 mm needle; longer in obese patients to clear subcutaneous fat.

Adrenaline dose — child

10 microg/kg IM (0.01 mL/kg of 1:1000), max 0.5 mg. Practical: > 12 yr 0.5 mg · 6–12 yr 0.3 mg · 6 mo–6 yr 0.15 mg · < 6 mo 0.1–0.15 mg.

Repeat

Every 5 minutes if no improvement in airway, breathing or circulation. There is no maximum — a third or fourth dose triggers the refractory pathway, not abandonment.

Supportive

Position

Supine with legs raised if hypotensive; sitting up only if pure respiratory distress; left lateral if pregnant > 20 weeks. Never stand the patient up — sudden empty-ventricle arrest is reported.

Fluids

Crystalloid 20 mL/kg rapid bolus (1 L adult), repeat to total 50 mL/kg in the first 30 min if needed. Loss of intravascular volume into the interstitium can be massive.

Indian-ED note

Adrenaline 1:1000 ampoules (1 mg/mL) are universally stocked under EDL — keep in resus drawer not crash trolley locked box. Cost is negligible; delays are nearly always recognition or training, not supply.

What NOT to lead with — common errors

These are the recurring mistakes that turn a survivable anaphylaxis into a death. Each one delays or replaces IM adrenaline.

Bedside key actions

What not to give

Steroids

Hydrocortisone and methylprednisolone do nothing in the first 30 minutes. RC UK 2021 (reaffirmed 2025) and ERC 2025 explicitly advise against routine corticosteroids — they neither prevent biphasic reactions nor speed recovery, and steroid use is associated with increased morbidity in observational data.

Antihistamines

Chlorphenamine treats urticaria and itch, not airway oedema or shock. Give AFTER adrenaline if at all; oral non-sedating agents (cetirizine 10 mg) are preferred.

What not to do

IV adrenaline

Reserve for peri-arrest or refractory shock with cardiac monitoring. Adult bolus 50 microg (0.5 mL of 1:10 000) titrated; or infusion 0.05–1 microg/kg/min. Bolus dosing in the awake patient causes ischaemia, arrhythmia and hypertensive crisis.

Technique

Route and site

Anterolateral thigh IM gives peak plasma levels at ~8 min; deltoid is slower and shallower; subcutaneous is unreliable in shock. Auto-injectors deliver into the thigh through clothing.

Pitfalls

Wait and watch

Every minute without adrenaline in true anaphylaxis raises the risk of biphasic deterioration and fatal upper airway obstruction. Recognition-to-adrenaline interval is the single biggest modifier of outcome.

Refractory anaphylaxis — when 2 IM doses are not enough

Defined as persistent symptoms after 2 appropriate IM doses. Move to an adrenaline infusion and call for senior airway and ICU support early.

Bedside key actions

Drugs

Adrenaline infusion

Mix 1 mg in 100 mL 0.9% saline = 10 microg/mL. Start at 0.05–0.1 microg/kg/min and titrate to MAP ≥ 65 mmHg. Run via central or large peripheral line with a clear label.

Glucagon

For patients on beta blockers who fail to respond — bypasses the beta receptor. Adult 1–5 mg IV over 5 min then infusion 5–15 microg/min; child 20–30 microg/kg, max 1 mg. Vomiting is common, protect the airway.

Specific issues

Bronchospasm

Salbutamol 5 mg + ipratropium 500 microg nebulised in oxygen. IV magnesium 2 g over 20 min for severe wheeze unresponsive to adrenaline.

Upper airway

Nebulised adrenaline 5 mg (5 mL of 1:1000) buys time but does not replace early intubation. Call airway-trained senior; have surgical cricothyrotomy kit ready — laryngeal oedema makes a difficult airway.

Escalation

Refractory shock

If MAP < 65 despite adrenaline infusion + 50 mL/kg crystalloid: add noradrenaline 0.05–0.5 microg/kg/min, then vasopressin 0.03 U/min. Methylene blue 1.5–2 mg/kg has anecdotal use in catecholamine-resistant cases.

Indian-ED note

Glucagon is not always stocked in district EDs — alert pharmacy when receiving a beta-blocked patient. Noradrenaline (1 mg/mL) ampoules are universally available; vasopressin often is not below tertiary centres.

Observation, biphasic risk and discharge

Every patient gets a minimum observation period stratified by severity. Discharge is conditional on adrenaline auto-injector, written plan, and allergy follow-up.

Bedside key actions

Observation duration

High-risk = 12 h

Required > 1 dose of adrenaline, severe asthma background, slow-onset reaction, ongoing trigger exposure, presentation in the evening (limits access to help if biphasic), known biphasic history, or remote home with no immediate access to care.

Moderate / standard = 6 h

Resolved with one IM dose, no high-risk features, reliable adult observer at home, lives within easy reach of emergency services.

Minimum = 2 h

Mild reaction, single IM dose, isolated cutaneous-respiratory features that resolved within minutes — applies only after senior review.

Discharge

Auto-injector

Prescribe 2 devices (adult 0.3 mg, child 15–30 kg 0.15 mg, child > 30 kg 0.3 mg). Demonstrate technique and trainer device before discharge — competence is the discharge criterion, not just the prescription.

Tryptase

Serum mast cell tryptase peaks 1–2 h after onset, falls to baseline by 24 h. Confirms diagnosis retrospectively when in doubt. Send all three samples; comparison to baseline matters more than a single value.

Indian-ED note

Adrenaline auto-injectors are not yet on the Indian EDL — supply is limited and costly (₹6000–8000 each). Where unavailable, train family to draw 0.5 mL from a 1 mg/mL ampoule with a 25 mm 23G needle; document this conversation. Allergy clinics exist in tertiary centres (AIIMS, PGI Chandigarh, CMC Vellore); 108 transfer for any recurrence.

Key takeaways

Adrenaline 0.5 mg IM into the anterolateral thigh is the only intervention that changes mortality. Give it the moment criteria are met — do not wait for hypotension.
Up to 1 in 5 patients have no skin signs. Sudden bronchospasm or hypotension after a likely allergen is anaphylaxis until proven otherwise.
Steroids and antihistamines treat the rash and the itch, not the airway or the shock. They are adjuncts and have no role in the first five minutes.
Refractory anaphylaxis (still unwell after 2 IM doses) needs an adrenaline infusion, not more boluses — and glucagon if the patient is on a beta blocker.
Discharge requires two auto-injectors, a written action plan, demonstrated technique, and an allergy clinic referral. Without these, the next reaction is the fatal one.

References

Freely citable

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Compiled from contemporary emergency-medicine practice and the guidelines listed above. For registered medical practitioners; not a substitute for clinical judgement.

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Recognising anaphylaxis — when to commit

Bedside key actions

First-line treatment — adrenaline IM

Bedside key actions

What NOT to lead with — common errors

Bedside key actions

Refractory anaphylaxis — when 2 IM doses are not enough

Bedside key actions

Observation, biphasic risk and discharge

Bedside key actions

🔑 Key takeaways

References

Test yourself

Like this chapter? There are 295 more.

Key takeaways