Anaphylaxis at the IMT (Internal Medicine Training) clinical station is answered with one drug, one dose and one interval: 500 micrograms of adrenaline intramuscularly into the anterolateral thigh, repeated after 5 minutes if the patient has not improved. The Resuscitation Council UK 2021 guideline defines anaphylaxis as sudden onset and rapid progression of life-threatening airway, breathing or circulation problems, usually with skin or mucosal changes.

Key takeaways

  • Resuscitation Council UK diagnoses anaphylaxis on sudden onset of airway, breathing or circulation problems, usually with skin or mucosal changes; skin changes are absent in 10 to 20 per cent of reactions.
  • Adults and children over 12 get 500 micrograms of adrenaline IM (0.5 mL of 1 mg/mL), repeated after 5 minutes if there is no improvement.
  • No improvement in breathing or circulation after two doses is refractory anaphylaxis: call for expert help to start a low-dose intravenous adrenaline infusion and give fluids.
  • In hypotension or a poor response to the first dose, give a rapid crystalloid bolus of 500 to 1,000 mL in an adult; up to 3 to 5 litres may be needed in severe shock.
  • Antihistamines are third line and corticosteroids are not routine; mast cell tryptase is sampled ideally within 2 hours of onset with a later baseline.
  • Observation after resolution is risk-stratified: 2 hours fast-track, 6 hours minimum after two doses of adrenaline, at least 12 hours after more than two doses or severe respiratory compromise.

How do you recognise anaphylaxis in the scenario?

Anaphylaxis is recognised from the pattern, not from the rash: sudden onset, rapid progression, and a life-threatening airway, breathing or circulation problem, according to Resuscitation Council UK. The station will describe a patient minutes into an antibiotic infusion with stridor, wheeze or a falling blood pressure.

Say explicitly that skin or mucosal changes alone, without an airway, breathing or circulation problem, are not anaphylaxis, and that skin changes can be subtle or absent in 10 to 20 per cent of reactions. That sentence shows the panel you know both edges of the definition.

What does the A to E assessment and first hour look like?

The first hour of anaphylaxis is an A to E assessment with adrenaline given as soon as a life-threatening feature is found, not after the assessment is complete. Resuscitation Council UK tells you to treat life-threatening features using the airway, breathing, circulation, disability, exposure approach and to give adrenaline early.

  • Call for help and stop any drug or infusion suspected of causing the reaction
  • Give 500 micrograms of adrenaline IM into the anterolateral thigh, and note the time
  • High-flow oxygen, and lie the patient flat with or without leg elevation if the blood pressure is low; sit them up if breathing is the main problem
  • Intravenous access and a rapid crystalloid bolus of 500 to 1,000 mL if there is hypotension or a poor response to the first adrenaline dose
  • Repeat the adrenaline after 5 minutes if there is no improvement, while securing access and monitoring

Which investigations matter in anaphylaxis?

Investigation never delays treatment in anaphylaxis, and the one specific test is mast cell tryptase. Resuscitation Council UK advises a minimum of one sample ideally within 2 hours of onset, when levels peak, with a later baseline sample so the rise can be interpreted.

A normal tryptase does not exclude anaphylaxis, and tryptase may not rise obviously in food-induced reactions. The rest of the workup is the standard set for any critically ill patient: gas, ECG and a documented timeline of every dose given.

What is the dose and interval you must state?

The threshold facts in anaphylaxis are 500 micrograms of adrenaline IM for adults and children over 12, drawn up as 0.5 mL of 1 mg/mL adrenaline, and a repeat after 5 minutes if there is no improvement. Peak absorption is around 5 to 10 minutes after an intramuscular injection, which is why the interval is 5 minutes and not 1.

Resuscitation Council UK adds that auto-injectors are not recommended for administration by healthcare staff in a hospital setting, since they cannot deliver a weight-appropriate dose in most patients. Say adrenaline from an ampoule, drawn up.

What is refractory anaphylaxis and how is it managed?

Refractory anaphylaxis is anaphylaxis needing ongoing treatment because breathing or circulation problems persist despite two appropriate doses of intramuscular adrenaline. Resuscitation Council UK says it needs a low-dose intravenous adrenaline infusion started with expert help, fluids, and critical care.

  • Continue IM adrenaline every 5 minutes until the infusion is running
  • Intravenous adrenaline boluses are not recommended outside cardiac arrest or by clinicians who use vasopressors routinely
  • Large-volume crystalloid, up to 3 to 5 litres in adults, using a balanced solution such as Hartmann's to limit hyperchloraemia
  • Consider corticosteroids after initial resuscitation for refractory reactions or ongoing asthma or shock, never in preference to adrenaline
  • Fewer than 1 per cent of reactions are refractory, so escalating early is the skill being tested

When and to whom do you escalate anaphylaxis?

Escalate anaphylaxis at the first dose: put out the emergency call, involve the anaesthetist for any airway threat, and call critical care as soon as a second adrenaline dose is needed. That said, the escalation the panel most wants to hear is the one after the event: referral to an allergy clinic.

How do you hand over anaphylaxis in one minute?

The anaphylaxis handover leads with the doses and the times. Situation: a 42 year old with anaphylaxis to co-amoxiclav, two doses of 500 micrograms IM adrenaline at 14:05 and 14:10, now improving. Background: no previous reactions, asthmatic. Assessment: wheeze resolved, blood pressure 118 over 70 after 1 litre of Hartmann's, tryptase sent at 14:40. Recommendation: monitored bed for at least 6 hours from resolution, non-sedating oral antihistamine for skin symptoms, allergy referral and auto-injector training before discharge.

What does the panel listen for in an anaphylaxis answer?

The panel listens for adrenaline before anything else, the correct dose and route, the 5-minute repeat, and the word refractory said with a plan attached. They also listen for what you do not say: chlorphenamine and hydrocortisone as first-line drugs date an answer to the 2008 guideline.

The observation period is the second discriminator. Resuscitation Council UK recommends fast-track discharge after 2 hours only if a single dose given within 30 minutes of onset produced a good response, symptoms have fully resolved, and the patient already has unused auto-injectors and knows how to use them. Two doses or a previous biphasic reaction means at least 6 hours; more than two doses, severe asthma or respiratory compromise, a slow-release allergen, or a late-night presentation means at least 12 hours. The internalmedicineinterview bank, 361 questions with AI-marked spoken practice, drills exactly these numbers.

What are the common mistakes in an anaphylaxis station?

  • Giving antihistamine or steroid first, or at all, before adrenaline
  • Intravenous adrenaline on a ward
  • Waiting for a rash before treating a patient with stridor and hypotension
  • Forgetting the 5-minute repeat and the refractory pathway
  • Sending home after 2 hours with no auto-injector, no training and no allergy referral

How this comes up at the IMT interview

Anaphylaxis maps onto the IMT clinical station as a management-heavy scenario. Investigations and diagnosis is the clinical definition and the tryptase timing; management is the adrenaline dose, the repeat, fluids and the refractory algorithm; communication is explaining the biphasic risk and the auto-injector plan to the patient. The handover minute is scored on times and doses said in order, and on naming the observation period you have chosen and why.