Anaphylaxis on the Ward

Anaphylaxis on the ward is treated with intramuscular adrenaline 500 micrograms into the anterolateral aspect of the middle third of the thigh, repeated after 5 minutes if the patient has not improved. According to the Resuscitation Council UK guideline of May 2021, which its website confirms is still the current version, the patient must not stand or sit up, because posture change alone has caused death. At the CT1 anaesthetics interview the marks are for the route, the repeat and the position.

Key takeaways

• Intramuscular adrenaline is first line in every healthcare setting: 500 micrograms of 1 mg/ml for adults and children over 12, which is 0.5 ml
• Repeat after 5 minutes if there is no improvement; no improvement in breathing or circulation after two doses means refractory anaphylaxis
• Fatality can occur within minutes if a patient stands, walks or sits up suddenly, so they must not walk or stand during the reaction
• Give a rapid fluid bolus of 500 to 1,000 ml in an adult if there is hypotension, shock or a poor response to the first dose, using a non-glucose crystalloid
• Antihistamines are not part of initial emergency treatment and corticosteroids are no longer routinely advised
• Observation is risk-stratified: 2 hours for a fast-track discharge, a minimum of 6 hours after two doses, and at least 12 hours after more than two doses

How do you recognise anaphylaxis on the ward?

Anaphylaxis on the ward is recognised as sudden airway, breathing or circulation problems after an exposure, usually with skin changes. The Resuscitation Council UK says adrenaline goes to every patient with those life-threatening features.

If those features are absent but there are other features of a systemic allergic reaction, the guideline asks for careful observation and symptomatic treatment using the ABCDE approach rather than immediate adrenaline.

On a ward the usual trigger is a drug or blood product being infused, so the first physical act is often stopping an infusion. Anaphylaxis can also follow food or a sting in a visiting relative.

What is the first thing you do?

The first things in ward anaphylaxis happen together: call for help, stop the trigger, lie the patient flat and give intramuscular adrenaline. The guideline makes clear that adrenaline should not wait for intravenous access.

• Stop any drug suspected of causing it, including a drug infusion or blood product, and stop a colloid infusion in any patient with possible anaphylaxis
• Remove a bee sting, where early removal matters more than the method, and never try to make the patient vomit
• Give 500 micrograms of adrenaline intramuscularly into the anterolateral middle third of the thigh with a green 21 gauge or blue 23 gauge needle
• Give the highest concentration of oxygen available using a mask with a reservoir, then adjust to a saturation of 94 to 98%
• Attach pulse oximetry, blood pressure and ECG monitoring as soon as possible to assess the response
• Measure respiratory rate, saturations, heart rate, blood pressure and conscious level, and listen for wheeze, to decide whether more adrenaline is needed

That said, do not delay definitive treatment if removing the trigger is not feasible. The adrenaline is the treatment; the trigger removal is housekeeping that can happen alongside it.

What dose of adrenaline, where, and how often?

The adult intramuscular dose in ward anaphylaxis is 500 micrograms of 1 mg/ml adrenaline, which is 0.5 ml, and the same dose applies to children over 12 unless they are small or prepubertal, when 300 micrograms is given.

Repeat after 5 minutes if the patient has not improved, and note that peak absorption occurs around 5 to 10 minutes after an intramuscular injection. Some guidelines suggest the contralateral thigh, although the evidence is uncertain.

Auto-injectors are not recommended in healthcare settings for patients needing more than one dose. Further doses come from an ampoule with a syringe and needle, which is a detail that reads as ward experience.

How should the patient be positioned?

Position is treatment in anaphylaxis, not comfort. The Resuscitation Council UK states that fatality can occur within minutes if a patient stands, walks or sits up suddenly, and that patients must not walk or stand during acute reactions.

Lying flat, with or without leg elevation, is used for a circulation problem, because it maximises venous return. Patients with airway or breathing problems may prefer to be semi-recumbent, which makes breathing easier.

An unconscious patient who is breathing normally goes into the recovery position with continuous monitoring. A pregnant patient lies on her left side to avoid aortocaval compression, and may be placed head down rather than having her legs lifted.

What else goes in, and what does not?

After adrenaline, fluid is the next thing that matters in ward anaphylaxis. The guideline gives a rapid bolus of 500 to 1,000 ml in an adult, or 10 ml/kg in a child, for hypotension, shock or a poor response to the first dose.

• Use a non-glucose-containing crystalloid with a sodium concentration of 130 to 154 mmol/L, such as 0.9% sodium chloride or Hartmann's
• Large volumes, up to 3 to 5 litres in an adult, may be needed for severe anaphylactic shock, preferring Hartmann's or Plasma-Lyte to limit hyperchloraemia
• Colloids are not recommended and are a recognised cause of anaphylaxis, so stop any colloid infusion
• Antihistamines are not part of the initial emergency treatment and have no role in respiratory or cardiovascular features
• Once stabilised, use a non-sedating oral antihistamine such as cetirizine 10 to 20 mg in an adult, in preference to chlorphenamine
• Routine corticosteroids are no longer advised; consider them after initial resuscitation for refractory reactions or ongoing asthma or shock

Research shows why the fluid matters: haematocrit measurements in one series indicated extravasation of up to 35% of circulating blood volume within 10 minutes of the reaction starting.

When is this refractory anaphylaxis?

Anaphylaxis is refractory when it needs ongoing treatment because respiratory or cardiovascular problems persist despite two appropriate doses of intramuscular adrenaline. The guideline notes that fewer than 1% of reactions reach this point.

At that point the Resuscitation Council UK asks for expert help to establish a low-dose intravenous adrenaline infusion, with continued intramuscular doses every 5 minutes until the infusion is running.

Intravenous adrenaline boluses are not recommended for refractory anaphylaxis unless the patient is in cardiac arrest, or the clinician routinely titrates vasopressors. Monitoring is mandatory: ECG, oximetry and non-invasive blood pressure at least every 5 minutes.

When do you take tryptase?

Mast cell tryptase is taken once the patient is stable, and never at the cost of treatment. The minimum is one sample ideally within 2 hours of symptom onset and no later than 4 hours.

Ideally three timed samples are taken: one as soon as feasible, a second 1 to 2 hours after onset and no later than 4 hours, and a third at least 24 hours after complete resolution or in convalescence as a baseline.

A raised level is defined as above 11.4 or 14 micrograms per litre, or above the convalescent value multiplied by 1.2 plus 2. A normal tryptase does not exclude anaphylaxis, and the result never guides acute care.

How long does the patient stay, and who follows them up?

Length of stay after ward anaphylaxis is risk-stratified rather than fixed, and every patient is reviewed by a senior clinician before any decision. Biphasic reactions occur in around 5% of patients, one in twenty.

• Fast-track discharge after 2 hours from resolution is considered only if a single dose given within 30 minutes of onset worked within 5 to 10 minutes, symptoms resolved completely, the patient already has unused auto-injectors and training, and supervision after discharge is adequate
• A minimum of 6 hours after resolution is recommended if two doses of intramuscular adrenaline were needed, or there has been a previous biphasic reaction
• At least 12 hours after resolution if more than two doses were needed, if there was severe asthma or severe respiratory compromise, if allergen absorption may continue as with slow-release medicines, if the patient presents late at night or could not respond to deterioration, or if access to emergency care is difficult
• Before discharge, patients should be asked to stand up and be assessed
• Discharge must comply with the NICE guideline on anaphylaxis, CG134, and referral for specialist allergy assessment follows

There is no reliable way to predict who will have a biphasic reaction, so the guideline leaves the decision with an experienced clinician for each patient rather than with a rule.

How does ward anaphylaxis differ from anaphylaxis under anaesthesia?

Ward anaphylaxis differs from the perioperative version mainly in route and in what is hidden. On the ward the first dose is intramuscular; under anaesthesia an anaesthetist with monitoring and access may give intravenous adrenaline in much smaller increments.

The Resuscitation Council UK is careful here. It says both routes are recommended perioperatively, but that international guidelines recommend intramuscular adrenaline first line in all settings, and that cardiac arrest experience alone does not justify intravenous use.

The perioperative presentation is covered in this library's article on perioperative anaphylaxis, including recognition under drapes and what NAP6 changed. Cross-reference it in your answer rather than repeating it.

Which mistakes cost marks in a ward anaphylaxis scenario?

The ward anaphylaxis mistakes are the ones the 2021 revision was written to remove, and several of them are things candidates were taught only a few years ago.

• Giving chlorphenamine and hydrocortisone early: antihistamines are not initial treatment and routine steroids are no longer advised
• Sitting the patient up to make them comfortable, when posture change has caused cardiovascular collapse and death
• Reaching for intravenous adrenaline as a first move outside theatre, where the intramuscular route is first line
• Waiting for a tryptase before treating, when the result is never available in time to guide acute care
• Discharging after 2 hours when two doses were needed, which the guideline puts in the 6-hour group
• Forgetting to stop the infusion or the colloid that caused the reaction

How this comes up at the CT1 anaesthetics interview

Ward anaphylaxis reaches the clinical judgement station as a crash bleep to a medical ward, often during an antibiotic or blood transfusion. The station is 15 minutes after five minutes of reading, marked out of 50 by two assessors.

Clinical judgement and decision making is scored on the dose, the route, the repeat and the position. Reflective practice is scored on how you would follow the patient up, and working under pressure on whether you recognise refractory anaphylaxis and escalate.

The follow-up usually pushes past the algorithm: two doses have not worked, or the patient arrests. anaestheticinterview's bank of 340 questions carries AI-marked spoken practice, which is the only way these sequences become fluent out loud.