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Anaphylaxis: how to make a swift diagnosis, treat, monitor and advise patients

What nurses should know about anaphylaxis, a systemic allergic reaction and medical emergency
Anaphylaxis

What nurses need to know about anaphylaxis, a systemic allergic reaction and medical emergency

  • Red flag symptoms are skin or mucosal changes such as redness, rash or hives, or swelling of the tongue, lips and eyes
  • The first line of treatment is intramuscular adrenaline, which should be given as swiftly as possible
  • Pulse, blood pressure, ECG and pulse oximetry must be monitored to assess patients response to adrenaline

Anaphylaxis is an extremely serious allergic reaction that sends an increasing number of patients to hospital with potentially life-threatening conditions.

Hospital admissions in the UK for food-related anaphylaxis increased by almost 6%

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What nurses need to know about anaphylaxis, a systemic allergic reaction and medical emergency

  • Red flag symptoms are skin or mucosal changes such as redness, rash or hives, or swelling of the tongue, lips and eyes
  • The first line of treatment is intramuscular adrenaline, which should be given as swiftly as possible
  • Pulse, blood pressure, ECG and pulse oximetry must be monitored to assess patient’s response to adrenaline
In some people, anaphylaxis may be triggered by nuts Picture: iStock

Anaphylaxis is an extremely serious allergic reaction that sends an increasing number of patients to hospital with potentially life-threatening conditions.

Hospital admissions in the UK for food-related anaphylaxis increased by almost 6% a year in the decade to 2018, according to a study published in the BMJ in February. In the 20 years to 2012, hospital admissions for anaphylaxis rose more than 600%.

Anaphylaxis facts and statistics

  • Anaphylaxis can be caused by a broad range of triggers, but the most common allergens identified include food, drugs and venom
  • Food is the most common cause of anaphylaxis in young people. Preschool-aged children have the highest rate of hospitalisation due to food-anaphylaxis, but a disproportionately low rate of fatal outcomes
  • The greatest risk from fatal food allergy appears to be in teenagers and adults up to age 30 years. The foods that trigger the most cases are tree nuts, peanuts and cows’ milk
  • In contrast, fatal anaphylaxis due to drugs is rare in children, and peaks in older people, presumably due to polypharmacy
  • Drugs cause the highest number of fatal anaphylaxis, at 39%. The most common triggers for fatal reactions are neuromuscular blocking agents, followed by antibiotics
  • For a significant proportion of anaphylaxis, the cause is never found

Source: Resuscitation Council 2012

Anaphylaxis, a systemic allergic reaction, is a medical emergency that requires immediate treatment. It causes rapidly developing symptoms that can affect the airway, breathing and circulation.

Confusion over diagnosis, treatment, investigation and follow-up of people with anaphylaxis

Anaphylaxis guidance from the Resuscitation Council UK, which is currently being updated, sets out the emergency care that should be given. The draft document says that despite previous guidelines there remains confusion over the diagnosis, treatment, investigation and follow-up of patients who have anaphylaxis.

The National Institute for Health and Care Excellence (NICE) says anaphylaxis care can leave much to be desired and many people do not receive optimal management of their condition.

For this, NICE blames healthcare professionals’ lack of understanding when making a diagnosis and failure to separate it from less severe histamine-releasing reactions or from other conditions that mimic some or all of its clinical features.

Patient is often anxious and may experience a sense of impending doom

The Resuscitation Council says anaphylaxis should be recognised by healthcare professionals from the patient’s exposure to something that is known to be an allergen for them, as well as sudden onset and rapid progression of symptoms that can affect the airway and breathing and cause circulation problems and skin and mucosal changes.

The patient will often feel and look unwell, and the reaction will develop quickly, over minutes. The patient is usually anxious and can experience a sense of impending doom.

Signs and symptoms of anaphylaxis

  • Airway swelling, such as throat and tongue swelling – patient has difficulty in breathing and/or swallowing and may complain that their throat is closing up
  • Hoarse voice
  • Stridor (a high-pitched inspiratory noise caused by upper airway obstruction)
  • Shortness of breath, increased respiratory rate
  • Wheeze and/or persistent cough
  • Patient becoming tired with the effort of breathing
  • Confusion caused by hypoxia
  • Cyanosis (mucous membranes appear blue) – this is usually a late sign
  • Respiratory arrest
  • Signs of shock – pale, clammy
  • Significant increase in heart rate (tachycardia)
  • Low blood pressure (hypotension) – feeling faint (dizziness), collapse
  • Decreased conscious level or loss of consciousness
  • Anaphylaxis can cause myocardial ischaemia and electrocardiograph (ECG) changes, even in individuals with normal coronary arteries
  • Cardiac arrest

Source: Resuscitation Council 2012

Allergens taking a parenteral route, such as an intravenous drug, intramuscular injection or insect sting, cause a more rapid onset of symptoms than reactions due to ingested food.

The first line treatment for anaphylaxis is intramuscular adrenaline, and this should be given as swiftly as possible. Confusion may arise because some patients have systemic reactions that are not anaphylaxis. If in doubt, the guidance says always give adrenaline, which is well tolerated, and then seek senior help.

‘The key thing is early recognition of symptoms, which tend to come on quickly and progress rapidly’

Holly Shaw, nurse adviser at Allergy UK

Holly Shaw, nurse adviser at charity Allergy UK, says: ‘The key thing is early recognition of symptoms, which tend to come on quickly and progress rapidly. It is life-threatening, because these symptoms affect the circulatory system and airway.

‘Symptoms that highlight problems with the airway may include breathing problems, a new and persistent cough, chest tightness, stridor and/or hoarse voice.

Red flag warning signs that could be a precursor to anaphylaxis

‘Eight out of ten people with anaphylaxis will have skin or mucosal changes, like redness, rash or hives, or swelling of the tongue, lips and eyes. These are a red flag, a warning sign, to monitor your patient closely, as these symptoms may be a precursor to anaphylaxis.’

The Anaphylaxis Campaign, a charity supporting people at risk of severe allergies, says the symptoms are caused by the sudden release of chemical substances, including histamine, from cells in the blood and tissues where they are stored.

The release is triggered by the interaction between an allergic antibody called immunoglobulin E (IgE) and the allergen. This mechanism is so sensitive that minute quantities of the allergen can cause a reaction. The released chemicals act on blood vessels to cause swelling.

ABCDE approach should be used for most serious problems facing a patient

Responding swiftly to symptoms is critical. Ms Shaw says: ‘The earlier symptoms are picked up, and the earlier that the patient gets adrenaline, the better the outcome.’

Patients may have self-administered this with an adrenaline autoinjector before arriving in hospital, or paramedics may have given it.

An adrenaline autoinjector
An adrenaline autoinjector Picture: Alamy

New draft guidance from the Resuscitation Council, due to be completed by the summer, says intramuscular adrenaline should be given every five minutes if features of anaphylaxis do not resolve.

The ABCDE (airway, breathing, circulation, disability, exposure) approach should be used to deal with the most serious problems facing the patient.

Healthcare staff should remove the trigger where possible, for example stop any drug treatment that is causing the reaction or remove the stinger from a bee sting.

Monitoring of the pulse, blood pressure, ECG and pulse oximetry should be started as soon as possible to help assess the patient’s response to adrenaline.

Treatment of anaphylaxis

Treatment of anaphylaxis should be based on general life support principles:

Patients having an anaphylactic reaction in any setting should expect the following as a minimum:

  • Recognition that they are seriously unwell
  • An early call for help
  • Initial assessment and treatments based on an ABCDE approach
  • Adrenaline therapy if indicated
  • Investigation and follow-up by an allergy specialist

Source: Resuscitation Council 2012

Patients should not be allowed to walk or stand during the acute phase

Oxygen should be given, and IV fluids set up in the presence of hypotension/shock, or poor response to initial adrenaline.

The Resuscitation Council draft guidance states that antihistamines are not recommended in the treatment of acute anaphylaxis, and routine use of corticosteroids is also not recommended, although it should be considered in some cases.

Also in the draft guidance is advice that patients should not be allowed to walk or stand during the acute phase, as it can lead to death within minutes from cardiovascular collapse.

Ms Shaw says getting a good history when a patient arrives at the emergency department (ED) is essential, either from the patient or their next of kin. This should include what allergen, if known, they have been exposed to, the route of exposure – such as was it a food that was eaten or an insect sting that was injected – timings from exposure to onset of symptoms, what the symptoms are and what treatment has taken place.

An insect sting can trigger a reaction more quickly than a food allergy

‘The type of allergen is important. An insect sting can get into the body and often trigger a reaction more quickly than a food allergy. The amount of the allergen consumed can also be critical,’ says Ms Shaw.

Other underlying conditions are also key, as fatalities from anaphylaxis can often occur in people who also have asthma, especially if it is poorly controlled.

‘The assessment needs to be prompt because of the rapid onset, but it is quite a visual reaction, so you can generally see quickly that a patient is experiencing anaphylaxis’

Stella Davey, emergency department matron

Kingston Hospital NHS Foundation Trust ED matron Stella Davey says anaphylactic patients in EDs can be divided into two main categories – those who arrive as a result of a reaction, and those who experience a reaction to a drug they have received in the department.

Kingston Hospital NHS Foundation Trust ED matron Stella Davey
Stella Davey Picture: David Gee

But the need for a quick response is always the same. ‘Anaphylaxis is always a time-critical situation,’ she says. ‘The assessment needs to be prompt because of the rapid onset, but it is quite a visual reaction, so you can generally see quickly that a patient is experiencing anaphylaxis.

‘Patients can present at different points of the reaction, as sometimes they will have started treatment themselves with an adrenaline autoinjector, or received it from paramedics, and sometimes not.

‘Some patients who have an adrenaline autoinjector can sometimes be reluctant to use it, so may arrive having not self-injected.’

Even patients who have injected themselves should seek emergency care

Ms Davey says the emergency care that patients should receive is clearly set out. ‘There is a clear algorithm from the Resuscitation Council that we all follow.’

Even patients who have injected themselves, and feel they are recovering, should seek emergency care, she says.

Monitoring of a patient with anaphylaxis is important
Picture: iStock

Fortunately, the overall prognosis of anaphylaxis is good, with a case fatality rate of under 1% in those presenting to hospitals in the UK. There are approximately 20 deaths reported each year due to anaphylaxis in the UK, although this may be a significant underestimate, the Resuscitation Council says. Around ten of these fatalities are related to food-anaphylaxis.

Care for patients after the initial, critical element has been treated is set out by NICE. This stresses documenting details of the symptoms of the reaction, and the patient history, and for patients aged over 16 taking timed blood samples for mast cell tryptase testing as soon as possible after emergency treatment has started, and a second sample, ideally within one to two hours – but no later than four hours – from the onset of symptoms.

Before discharge patients must be given advice on how to manage any further problems

This should be considered for those under 16 if the cause is thought to be venom-related, drug-related or idiopathic. Patients aged over 16 should generally be observed for six to 12 hours following their emergency treatment, and those under 16 should be admitted to hospital under the care of a paediatric team, NICE says.

Those who have received emergency treatment for suspected anaphylaxis should be referred to a specialist allergy service.

Before patients are discharged they must be given some education and advice on how to manage any further problems before seeing an allergy specialist. They should be told about anaphylaxis and what symptoms to look out for and about the risk of a biphasic reaction, which is a recurrence of the reaction without further exposure to the allergen.

Support groups such as Allergy UK offer opportunity to speak to others with similar experiences

Patients should be shown the correct way to use an adrenaline injector, told when to use it and given advice about how to avoid the suspected trigger. Importantly, people should be discharged with a prescription for two injectors and advised to carry them at all times.

Putting patients in touch with support groups such as Allergy UK can provide vital support after a traumatic event, says Ms Shaw. ‘The opportunity to speak to other people with the same experience can be useful,’ she says.

‘It is a big responsibility having a food or other allergy with a risk of anaphylaxis, which leads to daily risk assessments of things that many of us take for granted, such as eating out, getting a takeaway, or doing the food shopping. Talking to others about it can help.’


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