emergency

Angioedema

Deep swelling of the lips, tongue, face or airway. Management hinges on one question: is this histamine-mediated or bradykinin-mediated? Allergic angioedema usually comes with urticaria and itch and responds to adrenaline; ACE-inhibitor and…

Airway first — then histamine or bradykinin?

The pathway

1 · Airway first, before the diagnosis

Voice change, stridor, drooling, tongue protrusion — the airway is going
Sit them up if the airway or breathing is the dominant problem; lie a shocked patient flat with the legs raised
Do not let a shocked or anaphylactic patient stand or walk — sudden upright posture has been associated with cardiac arrest
Anaesthetics and ENT now for anything involving the tongue, floor of mouth or larynx
Plan for a difficult airway and a surgical airway in the room

2 · Urticaria or not — the question that decides treatment

WITH urticaria and itch → histamine-mediated (allergic). Treat as anaphylaxis if there is any airway, breathing or circulation compromise
WITHOUT urticaria or itch → bradykinin-mediated is likelier. Think ACE inhibitor or hereditary
It is a strong discriminator, not an absolute one — anaphylaxis can occur without skin features, so the absence of urticaria does not exclude it
Isolated swelling of lips and tongue with no rash, in someone on ramipril, is the commonest hospital version

3 · Histamine-mediated: treat as anaphylaxis

IM adrenaline 500 micrograms into the anterolateral thigh if any ABC compromise
Repeat every 5 minutes if there is no improvement
After two doses this is REFRACTORY anaphylaxis: call for expert and critical care help and start an adrenaline infusion. IM adrenaline continues every 5 minutes until that infusion is running
Give a fluid bolus — the shock is distributive
Antihistamine and steroid are adjuncts, not the treatment
Observe — biphasic reactions occur

4 · ACE-inhibitor angioedema

Can occur at any time, including after weeks to years — around half of reported cases begin 30 days or more after starting, so a long tolerated course does not exonerate it
Higher reported risk in older adults, women, people who smoke, and patients of Black or African Caribbean ethnicity
Stop the ACE inhibitor immediately and do not restart it; document it as an allergy
Bradykinin-mediated angioedema is unlikely to respond to standard anaphylaxis treatment, including adrenaline (MHRA, June 2026)
So: if anaphylaxis cannot confidently be excluded and there is ABC compromise, give IM adrenaline. In a clearly bradykinin-mediated presentation, adrenaline is not routine
Either way, do not delay airway management waiting for medication to work — that is the decision that changes the outcome
Lack of response to standard anaphylaxis treatment should itself prompt you to think bradykinin
Supportive airway care while it resolves over 24–72 hours
ARBs carry a lower but real risk — prescribe with caution

5 · Hereditary angioedema

Family history, recurrent attacks, often with abdominal pain attacks, no urticaria
Triggered by trauma, dental work, stress, oestrogens
Specific treatment: C1 esterase inhibitor concentrate, icatibant. Many patients carry their own
Ask the patient — they usually know their plan better than the department does

6 · Before they leave

Document the culprit on the allergy record, not just in the notes
ACE inhibitor: explain it must never be restarted, and tell the GP
Anaphylaxis: adrenaline auto-injector and allergy clinic referral
Recurrent with no cause: C4 and C1 inhibitor level as an outpatient

Drugs

Drug	Dose	Route	Notes
Adrenaline	500 micrograms IM (0.5ml of 1:1000), repeated every 5 min	IM	Anterolateral thigh. Give it whenever anaphylaxis cannot confidently be excluded and there is ABC compromise. In clearly bradykinin-mediated angioedema it is unlikely to work and is not routine. Two doses without improvement in a possible anaphylaxis = refractory anaphylaxis: expert help and an infusion, with IM continuing meanwhile.
Chlorphenamine	10mg	IV/IM	Adjunct in allergic angioedema. No role in ACE-inhibitor or hereditary.
Hydrocortisone	200mg	IV/IM	Adjunct in allergic angioedema. No role in bradykinin-mediated.
C1 esterase inhibitor / icatibant	Per patient's own plan	IV / SC	Hereditary angioedema. Ask the patient — many carry their own and know the dose.

When to escalate

Any voice change, stridor or tongue swelling — anaesthetics and ENT immediately,Possible anaphylaxis, no improvement after two doses of IM adrenaline — REFRACTORY anaphylaxis: critical care help and an adrenaline infusion, with IM continuing every 5 minutes until it runs,Known hereditary angioedema — give their specific treatment early, and involve immunology,Angioedema after thrombolysis — a recognised association, bradykinin-mediated, and the airway can close fast

Reference: Resuscitation Council UK Anaphylaxis Guidelines (2021) for the allergic arm. MHRA Drug Safety Update, 16 June 2026 — ACE inhibitors: the distinction between bradykinin- and histamine-mediated angioedema, which is the source for adrenaline being unlikely to work and not routine in the bradykinin arm. BSACI angioedema guidance. Local difficult-airway policy takes precedence.

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