Anaphylaxis is an immune-mediated reaction, which typically occurs when a person is exposed to a trigger, for example a food, drug, or insect sting. Onset of symptoms after exposure to a trigger can be within minutes or up to several hours later – this can be influenced by the route of exposure to the trigger, or the amount of allergen they are exposed to. In some instances, there can be no trigger established: this is known as ‘idiopathic anaphylaxis’ (Resuscitation Council United Kingdom [RCUK], 2021).
Anaphylaxis can be defined as:
‘a serious systemic hypersensitivity reaction that is usually rapid in onset and may cause death. Anaphylaxis is characterized by potentially life-threatening compromise in airway, breathing and/or the circulation, and may occur without typical skin features or circulatory shock being present.’
It is estimated that 1 in 300 people in Europe will experience anaphylaxis in their lifetime (Panesar et al, 2013). The incidence of anaphylaxis has increased significantly in recent years; it is estimated that there are around 20 deaths each year due to anaphylaxis in the UK (Turner et al, 2015). Therefore, it is important that health professionals can recognise and manage this life-threatening emergency. It is recommended that staff who give immunisations should have annual updates in the treatment of anaphylaxis (RCUK, 2021).
What are the signs and symptoms?
RCUK (2021) recommends that anaphylaxis can be recognised based on:
- Sudden onset and rapid progression of symptoms
- Exposure to a known/suspected allergen
- The presence of one or more airway and/or breathing and/or circulatory symptoms (see Figure 1).
Figure 1. Signs and symptoms of anaphylaxis
An allergic reaction results from the interaction of an allergen with specific immunoglobulin E (IgE) antibodies bound to receptors on mast cells and basophils. If an allergen binds with IgE molecules in sufficient quantity, cross linking of the IgE molecules and intracellular signalling occurs resulting in degranulation of the mast cell or basophil. Pre-formed chemical mediators are released including histamine, prostaglandin D2, leukotriene C4 and tryptase (Kemp and Lockey, 2002).
The cardiovascular effects of this histamine release are vasodilation, post capillary venule leakage, reduced vascular resistance, hypotension and flushing. Meanwhile, in the airways, tissue oedema and smooth muscle contraction can cause bronchospasm, wheeze, and/or laryngeal symptoms. Hypotension in anaphylaxis is defined as a drop in 30% from the patient's baseline, or a systolic of less than 90 mmHg in adult patients (RCUK, 2021).
Aside from the physiological symptoms, patients often describe feeling ‘an impending sense of doom’ during anaphylaxis.
Which patients are at risk of anaphylaxis?
Any person can develop anaphylaxis at any time during their life. Those who are ‘atopic’ (i.e. have a history of asthma, eczema, allergic rhinitis) are more likely to develop an allergy (National Institute for Health and Care Excellence [NICE], 2011a).
In order for a diagnosis of IgE-mediated allergy to be made, a patient will often undergo skin prick testing or have a specific IgE blood test. The results of these tests only give us a likelihood of reacting if the patient were exposed to that allergen: it cannot predict the severity of their reaction. As there is no way of predicting the severity, all patients with an allergy are treated with the same level of caution. Strict avoidance of the trigger is recommended (NICE, 2011a).
However, certain groups may be at higher risk of anaphylaxis (Turner et al, 2017). This can be due to an existing co-morbidity, or because they may be more likely to be exposed to the same allergen again.
Asthma
Patients with uncontrolled asthma are at greater risk of having anaphylaxis if exposed to an allergen than patients whose asthma is well controlled. Regular asthma reviews and adherence to prescribed asthma medication is important to minimise risk.
Adolescents
Data shows that teenagers are a high risk group, as they enter the world of managing allergen avoidance without parental support, and are more prone to risky behaviours as they try to ‘fit in’ with their peer group.
Previous anaphylaxis
Evidence shows that there is an increased risk of anaphylaxis when the patient has previously experienced a severe reaction (Gupta et al, 2004).
Type of allergy
A recent review of anaphylaxis deaths in the UK between 1998 and 2018 (Baseggio Conrado et al, 2021) showed that 26% of deaths in school-aged children were triggered by cow's milk. In adults, peanuts and tree nuts were responsible for 52% of fatalities. Some allergens are more easily avoided than others, for example it is easier to avoid penicillin than it is a wasp sting.
How is anaphylaxis treated?
If you are able to remove the trigger then this should be done, for example, if giving IV antibiotics, stop administering. If the patient has been stung by an insect, remove the sting. It is not recommend to induce vomiting if the patient is reacting to something they have eaten.
The first-line treatment for a patient experiencing anaphylaxis continues to be intramuscular (IM) adrenaline. Delay in administration of IM adrenaline brings a risk of fatality (RCUK, 2021). If anaphylaxis symptoms do not resolve, the dose should be repeated every 5 minutes. The doses listed in Table 1 are as per the current UK Resuscitation Council guidelines (RCUK, 2021). The position of the patient is important while managing anaphylaxis: they should be either lying flat on the floor (legs can be raised to encourage venous return if appropriate), or if breathing is difficult, they can be sat up with legs outstretched. Patients should not stand or walk during or following anaphylaxis. Change in posture from laying to sitting, or to standing, is associated with cardiovascular collapse and can be fatal (RCUK, 2021).
Table 1.
| Age | Dose of 1:1000 adrenaline (IM) |
|---|---|
| Adult and child >12 years | 500 micrograms or 0.5 ml |
| Child 6-12 years | 300 micrograms or 0.3 ml |
| Child 6 months–6 years | 150 micrograms or 0.15 ml |
| Child <6 months | 100–150 micrograms or 0.1–0.15 ml |
High-flow oxygen via facemask should be applied if available, and depending on where the anaphylaxis is being managed, a call for help should be made. If dialling 999, the word ‘anaphylaxis’ should be stated to communicate the life-threatening nature of the situation.
If the patient is still unwell, you may wish to secure IV access if this is available in the clinical area. However, doses of IM adrenaline should still be administered every 5 minutes while attempting to secure IV access. An IV bolus of non-glucose-containing crystalloid fluids can be administered. Inhaled bronchodilator therapy (eg salbutamol) may be considered in cases where two doses of adrenaline have been administered and the patient is still experiencing breathing difficulties.
Newly published anaphylaxis guidelines (RCUK, 2021) no longer recommend hydrocortisone for the routine emergency treatment of anaphylaxis. Oral cetirizine is preferable to IV chlorphenamine for patients with persistent skin symptoms after initial stabilisation.
NICE (2020) recommend that a person who has experienced suspected anaphylaxis should be observed for 6–12 hours after onset of symptoms in hospital, and children should be admitted overnight. This is due to the risk of biphasic anaphylaxis, which is rare, but can occur after complete recovery from the initial reaction. It is a recurrence of symptoms within 72 hours with no further exposure to the allergen. It is managed in the same way as anaphylaxis. Patients with uncontrolled asthma are more at risk of biphasic reactions.
How should these patients be managed going forwards?
NICE (2011b) recommend that an age-appropriate referral should be made to a specialist allergy service. Where possible, that referral should include as much detail as possible about the symptoms experienced by the patient during the episode, the timing of symptoms, and a record of the circumstances before the reaction commenced. This information may help identify a possible trigger, and is often poorly recalled by the patient.
As an interim measure, the patient should be prescribed two adrenaline auto-injectors (AAIs). They should receive a demonstration of how to use the specific device they have been prescribed, and be advised to carry their emergency medication with them at all times. They should be trained in how to manage an anaphylactic reaction should it occur and be guided in how to avoid the suspected trigger (if known).
The Medicines and Healthcare Products Regulatory Agency (MHRA) has recommended that anyone at risk of anaphylaxis should have 2 AAI devices immediately available at all times. This is due to the risk that one dose is not sufficient to manage the reaction. This is particularly relevant since the only AAI device to deliver the recommended adult dose of adrenaline (0.5 mg Emerade®) has been recalled from the market (MHRA, 2019).
The British Society of Allergy and Clinical Immunology (BSACI) offer ‘Allergy Action Plans’ for children (adult plans are in press currently). The plans are device specific (depending on which brand of AAI is prescribed), and can be given to support management of anaphylaxis in the community. Most schools or nurseries will ask for a copy of this document to be kept alongside the patient's emergency medication. These documents are free to download (www.bsaci.org).
Patients should be signposted to Allergy UK for access to reliable support and information via their website (www.allergyuk.org) or helpline. Likewise The Anaphylaxis Campaign provides practical advice for patients of all ages, schools, and families (www.anaphylaxis.org.uk).
Referral to a specialist service facilitates allergy testing, leading to diagnosis, expert advice around avoiding triggers, dietetic support if required and ongoing follow-up and support in managing allergy. This can reduce anxiety and improve quality of life for patients.
Conclusion
Anaphylaxis is a life-threatening emergency, and should be managed with IM adrenaline as first-line treatment. Correct diagnosis, avoidance of triggers and patient education are fundamental in reducing the risk of further episodes of anaphylaxis. Practice nurses can play a key role in supporting patients in the community, particularly those with allergies and uncontrolled or poorly managed asthma.
Useful resources:
- British Society of Allergy and Clinical Immunology (BSACI) have allergy action plans for children. Adult action plans are being developed. Free to download at: www.bsaci.org
- Allergy UK has support and information for patients via their website (www.allergyuk.org) or helpline (01322 619898)
- The Anaphylaxis Campaign provides practical advice for patients of all ages, schools, and families (www.anaphylaxis.org.uk)
KEY POINTS:
- Anaphylaxis is a life-threatening emergency, and should be managed with intramuscular (IM) adrenaline as first line treatment
- Correct diagnosis, avoidance and patient education are fundamental in reducing risk
- Practice nurses can play a key role in supporting patients in the community, particularly those with allergies and uncontrolled or poorly managed asthma
CPD reflective practice:
- What are the signs and symptoms of anaphylaxis?
- How is anaphylaxis treated?
- How should patients who have experienced anaphylaxis be managed going forwards?