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Anaphylaxis | Acute Management | ABCDE

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This guide provides an overview of the recognition and immediate management of anaphylaxis using an ABCDE approach.

The ABCDE approach is used to systematically assess an acutely unwell patient. It involves working through the following steps:

  • Airway
  • Breathing
  • Circulation
  • Disability
  • Exposure

Each stage of the ABCDE approach involves clinical assessment, investigations and interventions. Problems are addressed as they are identified, and the patient is re-assessed regularly to monitor their response to treatment.

This guide has been created to assist healthcare students in preparing for emergency simulation sessions as part of their training. It is not intended to be relied upon for patient care.


Clinical features

The clinical presentation of anaphylaxis can be variable, and making an early diagnosis can be challenging. 

The Resuscitation Council (UK) have devised the following set of criteria that, if met, suggest anaphylaxis is likely:

  • Sudden onset and rapid progression of symptoms (most reactions occur over several minutes)
  • Life-threatening airway and/or breathing and/or circulation problems
  • Skin and/or mucosal changes (flushing, urticaria, angioedema): however, these can be subtle or absent in up to 20% of reactions

Skin or mucosal changes alone are not a sign of an anaphylactic reaction. There can also be gastrointestinal symptoms (e.g. vomiting, abdominal pain, incontinence).

A history of exposure to a known allergen also helps support the diagnosis of anaphylaxis. Common allergens that can cause anaphylaxis are foods (most commonly nuts), medications, and insect stings/venom.

Treatment algorithm

Anaphylaxis treatment algorithm
Anaphylaxis treatment algorithm. Reproduced with the kind permission of Resuscitation Council UK
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Tips before you begin

General tips for applying an ABCDE approach in an emergency setting include:

  • Treat problems as you discover them and re-assess after every intervention
  • Remember to assess the front and back of the patient when carrying out your assessment (e.g. looking underneath the patient’s legs or at their back for non-blanching rashes or bleeding)
  • If the patient loses consciousness and there are no signs of life, put out a crash call and commence CPR
  • Make use of the team around you by delegating tasks where appropriate
  • All critically unwell patients should have continuous monitoring equipment attached
  • If you require senior input, call for help early using an appropriate SBAR handover
  • Review results as they become available (e.g. laboratory investigations)
  • Use local guidelines and algorithms to manage specific scenarios (e.g. acute asthma)
  • Any medications or fluids must be prescribed at the time (you may be able to delegate this to another staff member)
  • Your assessment and management should be documented clearly in the notes; however, this should not delay management
Methodical approach

For each section of the ABCDE assessment (e.g. airway, breathing, circulation etc.), ask yourself: 

  • Have I checked the relevant observations for this section? (e.g. checking respiratory rate and SpO2 as part of your ‘breathing’ assessment)
  • Have I examined the relevant parts of the system in this section? (e.g. peripheral perfusion, pulses, JVP, heart sounds, and peripheral oedema as part of your ‘circulation’ assessment)
  • Have I requested relevant investigations based on my findings from the initial clinical assessment? (e.g. capillary blood glucose as part of your ‘disability’ assessment)
  • Have I intervened to correct the issues I have identified? (e.g. administering IV fluids in response to fluid depletion/hypotension as part of your ‘circulation’ assessment)

Initial steps

Acute scenarios typically begin with a brief handover, including the patient’s nameagebackground and the reason the review has been requested.

You may be asked to review a patient with anaphylaxis due to rash, facial swelling, shortness of breath and/or wheeze.

If anaphylaxis is suspected, potential anaphylactoid triggers should be removed immediately (e.g. stop intravenous antibiotics).

You should also ask another staff member to source adrenaline (1:1000) to allow this to be administered as soon as you have confirmed the diagnosis (there is often an emergency box containing the relevant drugs).


Introduce yourself to whoever has requested a review of the patient and listen carefully to their handover.


Ensure the patient’s notesobservation chart, and prescription chart are easily accessible.

Ask for another clinical member of staff to assist you if possible.


Introduce yourself to the patient, including your name and role.

Ask how the patient is feeling, as this may provide useful information about their condition.

If the patient is unconscious or unresponsive, and there are no signs of life, start the basic life support (BLS) algorithm as per resuscitation guidelines.


Clinical assessment

Can the patient talk?

Yes: if the patient can talk, their airway is patent, and you can move on to the assessment of breathing.


  • Look for signs of airway compromise: angioedema (typically associated with anaphylaxis), cyanosis, see-saw breathing, use of accessory muscles and stridor.
  • Listen for abnormal airway noises: stridor, snoring, gurgling
  • Note any evidence of airway swelling, such as pharyngeal/laryngeal oedema causing the patient to have difficulty speaking (hoarse voice), breathing, and swallowing (the patient may complain of feeling like their airway is closing up)
  • Open the mouth and inspect: look for anything obstructing the airway, such as secretions or a foreign object.


Regardless of the underlying cause of airway obstruction, seek immediate expert support from an anaesthetist and the emergency medical team (often called the ‘crash team’). You can perform basic airway manoeuvres to help maintain the airway whilst awaiting senior input.

Head-tilt chin-lift manoeuvre

Open the patient’s airway using a head-tilt chin-lift manoeuvre:

  1. Place one hand on the patient’s forehead and the other under the chin
  2. Tilt the forehead back whilst lifting the chin forwards to extend the neck
  3. Inspect the airway for obvious obstruction. If an obstruction is visible within the airway, use a finger sweep or suction to try and remove it. Be careful not to push it further into the airway.

Jaw thrust

If the patient is suspected of having suffered significant trauma with potential spinal involvement, perform a jaw-thrust rather than a head-tilt chin-lift manoeuvre:

  1. Identify the angle of the mandible
  2. Place two fingers under the angle of the mandible (on both sides) and anchor your thumbs on the patient’s cheeks
  3. Lift the mandible forwards

Other interventions

Airway adjuncts are helpful and, in some cases, essential to maintain a patient’s airway. They should be used in conjunction with the manoeuvres mentioned above.

An oropharyngeal airway is a curved plastic tube with a flange on one end that sits between the tongue and hard palate to relieve soft palate obstruction. It should only be inserted in unconscious patients as it may induce gagging and aspiration in semi-conscious patients. 

nasopharyngeal airway is a soft plastic tube with a bevel at one end and a flange at the other. NPAs are typically better tolerated in partly or fully conscious patients than oropharyngeal airways.

Intramuscular (IM) adrenaline

IM adrenaline is the first-line treatment for anaphylaxis. It should be administered as soon as anaphylaxis is suspected. Delayed administration of adrenaline is associated with worse outcomes, and adrenaline must not be delayed to perform other investigations (e.g. ECG, ABG).2

The adult dose is 0.5 mL of 1:1000 adrenaline administered intramuscularly into the anterolateral aspect of the middle third of the thigh. 

If there is no response, a second dose can be administered after 5 minutes. If the patient remains haemodynamically unstable after two doses, an adrenaline infusion may be required (this will be a consultant/critical care-led decision). 


Make sure to re-assess the patient after any intervention.


Clinical assessment


Review the patient’s respiratory rate:

  • normal respiratory rate is between 12-20 breaths per minute
  • Tachypnoea is a common feature of anaphylaxis and indicates significant respiratory compromise
  • Bradypnoea in the context of hypoxia is a sign of impending respiratory failure and the need for urgent critical care review

Review the patient’s oxygen saturation (SpO2):

  • normal SpOrange is 94-98% in healthy individuals and 88-92% in patients with COPD at high risk of COretention
  • Hypoxaemia is a typical clinical feature of anaphylaxis


Auscultate the patient’s chest and identify any abnormalities such as:

  • Wheeze is a common finding in anaphylaxis (it can become less apparent with increasing airway obstruction)
  • Reduced air entry (sometimes called a ‘silent chest’) is a concerning finding indicating significant airway compromise and a need for senior clinical input

Investigations and procedures

Arterial blood gas

Take an ABG if indicated (e.g. low SpO2) to quantify the degree of hypoxia.

An ABG should not delay the management of anaphylaxis with IM adrenaline. 

Chest X-ray

A chest X-ray may be useful in ruling out other respiratory diagnoses if shortness of breath is the primary issue (e.g. pneumothorax, pneumonia, pulmonary oedema). Chest X-ray should not delay the emergency management of anaphylaxis and should only be performed if the diagnosis is in doubt.


Patient positioning

Patients with airway or breathing problems can be placed in a semi-recumbent position to aid breathing. However, patients with hypotension should be laid flat and sudden changes in posture must be avoided. 


Administer oxygen to all critically unwell patients during your initial assessment. This typically involves using a non-rebreathe mask with an oxygen flow rate of 15L.

Nebulised bronchodilators

Administer nebulised bronchodilators if there is evidence of bronchospasm (e.g. wheezing on auscultation):

  • Salbutamol: doses can vary; continuous nebulisation is advised in severe cases.
  • Ipratropium bromide: 500mcg nebulised


Make sure to re-assess the patient after any intervention.


Clinical assessment


Tachycardia is a common finding in anaphylaxis, and bradycardia is a late sign often suggestive that the patient is peri-arrest.

Blood pressure

A severe allergic reaction typically causes a drop in blood pressure (hypotension). The patient may complain of feeling faint or lose consciousness if hypotension is severe.

Anaphylactic shock may occur if there is a significant shift of fluid into the third space (into tissues) as part of the allergic response. This is a type of distributive shock which causes significant hypotension.

Clinical examination

Patients with anaphylaxis are typically peripherally cool, with a thready pulse and prolonged capillary refill time.

Fluid balance assessment

Calculate the patient’s fluid balance:

  • Calculate the patient’s current fluid balance using their fluid balance chart (e.g. oral fluids, intravenous fluids, urine output, drain output, stool output, vomiting) to inform resuscitation efforts.
  • Reduced urine output (oliguria) is typically defined as less than 0.5ml/kg/hour in an adult.

Investigations and procedures

Intravenous cannulation

Insert two wide-bore intravenous cannulas (14G or 16G) and take blood tests as discussed below.

See our intravenous cannulation guide for more details.

Blood tests

Request a full blood count (FBC)urea & electrolytes (U&E) and liver function tests (LFTs) for all acutely unwell patients. In the context of anaphylaxis, also request:

  • Mast cell tryptase: useful later to support the diagnosis of anaphylaxis


An ECG should be performed to identify evidence of acute myocardial ischaemia secondary to anaphylaxis.²

An ECG should not delay the emergency management of anaphylaxis.


Fluid resuscitation

Patients with anaphylaxis require urgent fluid resuscitation:2

  • Administer an initial bolus of 500-1000ml Hartmann’s solution or 0.9% sodium chloride over less than 15 mins
  • Re-assess the patient after each fluid bolus and administer further boluses as required (large volumes of fluid may be required in the context of anaphylaxis)
  • Patients who are unresponsive to fluid resuscitation will require critical care input


Make sure to re-assess the patient after any intervention.


Clinical assessment


In anaphylaxis, a patient’s consciousness level may be reduced secondary to hypoxia or hypovolaemia.

Assess the patient’s level of consciousness using the ACVPU scale:

  • Alert: the patient is fully alert
  • Confusion: the patient has new onset confusion or worse confusion than usual
  • Verbal: the patient makes some kind of response when you talk to them (e.g. words, grunt)
  • Pain: the patient responds to a painful stimulus (e.g. supraorbital pressure)
  • Unresponsive: the patient does not show evidence of any eye, voice or motor responses to pain

If a more detailed assessment of the patient’s level of consciousness is required, use the Glasgow Coma Scale (GCS).


Assess the patient’s pupils:

  • Inspect the size and symmetry of the patient’s pupils
  • Assess direct and consensual pupillary responses

Brief neurological assessment

Perform a brief neurological assessment by asking the patient to move their limbs. 

If a patient cannot move one or all of their limbs, this may be a sign of focal neurological impairment, which requires a more detailed assessment.

Drug chart review

Review the patient’s drug chart for medications which may cause neurological abnormalities (e.g. opioids, sedatives, anxiolytics).

Also, look for medications which may have caused the anaphylactic reaction.

  • Are the patient’s allergies documented on their drug chart?
  • If so, is there anything on the drug chart that has been prescribed and given in error?
  • Has the correct drug chart been used for the correct patient?


Blood glucose and ketones

Measure the patient’s capillary blood glucose level to screen for abnormalities (e.g. hypoglycaemia or hyperglycaemia). 

A blood glucose level may already be available from earlier investigations (e.g. ABG, venepuncture).

The normal reference range for fasting plasma glucose is 4.0 – 5.8 mmol/l.

Hypoglycaemia is defined as a plasma glucose of less than 3.0 mmol/l. In hospitalised patients, a blood glucose ≤4.0 mmol/L should be treated if the patient is symptomatic.

If the blood glucose is elevated, check ketone levels which, if also elevated, may suggest a diagnosis of diabetic ketoacidosis (DKA).

See our blood glucose measurement, hypoglycaemia and diabetic ketoacidosis guides for more details.


Maintain the airway

Alert a senior clinician immediately if you have concerns about a patient’s consciousness level.

A GCS of 8 or below, or a P or U on the ACVPU scale, warrants urgent expert help from an anaesthetist. In the meantime, you should re-assess and maintain the patient’s airway, as explained in the airway section of this guide.

Correct hypoglycaemia

Hypoglycaemia should always be considered in patients presenting with a reduced level of consciousness, regardless of whether they have diabetes. The management of hypoglycaemia involves the administration of glucose (e.g. oral or intravenous).


Make sure to re-assess the patient after any intervention.


Clinical assessment


Inspect for evidence of anaphylaxis, such as an urticarial rash and angioedema.

Look for potential allergens (e.g. an intravenous antibiotic infusion, wasp sting, recently consumed food).

Review the output of the patient’s catheter and any surgical drains.


Allergen removal

If a potential allergen is identified, remove the allergen (e.g. stop the antibiotic infusion).


Non-sedating oral antihistamines (e.g. cetirizine) can treat skin symptoms once the patient has been stabilised. Antihistamines are not used in the emergency management of anaphylaxis.

Discontinue causative medications and record allergy

Ensure that any medications on the drug chart are removed if they are believed to have caused the reaction.

Ensure that the patient’s allergies are updated and recorded.


Make sure to re-assess the patient after any intervention.

Re-assessment and escalation

Re-assess the patient using the ABCDE approach to identify any changes in their clinical condition and assess the effectiveness of your previous interventions.

Any clinical deterioration should be recognised quickly and acted upon immediately.

Seek senior help if the patient shows no signs of improvement or if you have any concerns.


Patients with anaphylaxis who are not responding to treatment (refractory anaphylaxis) will require urgent critical care input

Use an effective SBAR handover to communicate the key information to other medical staff.

Next steps

Take a history

Revisit history taking to identify triggers for anaphylaxis and explore relevant medical history.

See our history taking guides for more details.

Review medical records

Review the patient’s notes, charts and recent investigation results.

Review the patient’s current medications and check for any allergies


Discuss the patient’s clinical condition with a senior clinician using an SBAR handover.

Questions which may need to be considered include:

  • Are any further assessments or interventions required?
  • Does the patient need a referral to HDU/ICU?
  • Does the patient need reviewing by a specialist?
  • Should any changes be made to the current management of their underlying condition(s)?

The next team of clinicians on shift should be informed of any acutely unwell patient.


Clearly document your ABCDE assessment, including history, examination, observations, investigations, interventions, and the patient’s response.

The ABCDE approach can also form the structure for documenting your assessment.

See our documentation guides for more details.


Dr Leah Williams



Dr Chris Jefferies


  1. Resuscitation Council (UK). Emergency treatment of anaphylactic reactions: Guidelines for healthcare providers. Available from: [LINK].

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