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Anaphylaxis
Executive Editor, InnovAiT
General Practitioner, Hampshire, UK
E-mail: chantal.simon{at}oxfordjournals.org
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Abstract |
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 TOP Abstract Anaphylaxis and the GP...Causes of anaphylaxisFeaturesAirway, Breathing and...Differential diagnosisManagement of anaphylaxisCardiorespiratory arrest...Follow-upReferences |
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Anaphylaxis is a severe, systemic allergic reaction that is life threatening. Although less than 1% of those that suffer an anaphylactic attack die as a result of that attack, in the UK, there are approximately 20 deaths each year from anaphylaxis (one death per 3 million population). Risk of death is increased in those with pre-existing asthma, particularly, if the asthma is poorly controlled. Half of all fatalities due to anaphylaxis result from circulatory collapse (shock) and the remainder from respiratory failure (asphyxia). Prompt recognition and appropriate management saves lives.
Assessment and management of anaphylactic reactions is covered in GP Curriculum statement7: Care of Acutely Ill People. It is important for GPs to be able to recognize and evaluate acutely ill patients, such as those having an anaphylactic reaction, in the surgery, the patient's home or elsewhere, and manage them appropriately in line with National protocols.
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Causes of anaphylaxis |
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TOPAbstractAnaphylaxis and the GP...Causes of anaphylaxisFeaturesAirway, Breathing and...Differential diagnosisManagement of anaphylaxisCardiorespiratory arrest...Follow-upReferences |
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The most common causes of anaphylaxis in the UK are food allergies. It is estimated that up to 1 in 70 children have some allergic response to peanuts and 1 in 200 have anaphylactic reactions to peanuts. Incidence is increasing for reasons that are unclear. Other common causes of anaphylaxis include bee or wasp stings, drugs and latex. Drugs are the most common cause of death from anaphylaxis (table 1).
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Features |
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TOPAbstractAnaphylaxis and the GP...Causes of anaphylaxisFeaturesAirway, Breathing and...Differential diagnosisManagement of anaphylaxisCardiorespiratory arrest...Follow-upReferences |
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There is often a history of anaphylaxis or severe allergic reaction. Exposure to a known allergen should alert you to the possibility of anaphylaxis. However, anaphylaxis may occur on first exposure to the allergen.
Anaphylaxis is likely when all of the following three criteria are met:
- Sudden onset and rapid progression of symptoms usually over a period of minutes
- Life-threatening Airway and/or Breathing and/or Circulation problems
- Skin and/or mucosal changes—flushing, erythema, urticaria (Fig. 1—superficial, itchy swellings of the skin) and/or angio-oedema (Fig. 2—deep swelling of the skin and alimentary tract most commonly affecting the eyes, lips, genitalia, hands and/or feet), rhinitis and/or conjunctivitis
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However, skin and mucosal changes can be subtle or absent in up to one in five reactions. Indeed, some patients present with hypotension alone. Skin or mucosal changes alone are not a sign of an anaphylactic reaction, although they may develop into one. Other symptoms include abdominal symptoms such as abdominal pain, vomiting or incontinence. Often patients are also anxious and have a sense of impending doom.
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Airway, Breathing and Circulation |
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TOPAbstractAnaphylaxis and the GP...Causes of anaphylaxisFeaturesAirway, Breathing and...Differential diagnosisManagement of anaphylaxisCardiorespiratory arrest...Follow-upReferences |
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Patients suffering an anaphylactic reaction may have an Airway or Breathing or Circulation problem or any combination of these.
Airway problems
If a patient has difficulty breathing and swallowing and feels as if his/her throat is closing up, suspect airway swelling. Other possible signs include hoarseness caused by oedema of the vocal cords and stridor caused by narrowing of the upper airways.
Breathing problems
Breathing problems can present in a wide variety of ways, from a feeling of shortness of breath to respiratory arrest. Increased respiratory rate is common as is wheeze. The patient may become tired due to the effort of breathing and confused due to cerebral hypoxia. The patient may have reduced oxygen saturations (less than 92% saturation). Cyanosis is a late sign.
Sometimes, it is difficult to distinguish asthma from anaphylaxis and there is considerable overlap. Life-threatening asthma with no features of anaphylaxis can be triggered by food allergy. On the other hand, anaphylaxis can present as a primary respiratory arrest. If the patient has asthma-like features alone, follow the British Thoracic Society asthma guidelines (available from website: www.brit-thoracic.org.uk).
Circulation problems
The patient has signs of shock. For this reasons, circulation problems as a result of anaphylaxis are often referred to as ‘anaphylactic shock’. The patient is pale and clammy and usually tachycardic. Bradycardia is a late feature, often preceding cardiac arrest. Blood pressure is low and the patient may feel faint, dizzy or collapse. Cerebral hypoxia due to reduced perfusion may result in agitation or confusion or loss of consciousness. Anaphylaxis can cause myocardial ischaemia and electrocardiogram (ECG) changes even in individuals with normal coronary arteries.
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Differential diagnosis |
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TOPAbstractAnaphylaxis and the GP...Causes of anaphylaxisFeaturesAirway, Breathing and...Differential diagnosisManagement of anaphylaxisCardiorespiratory arrest...Follow-upReferences |
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Life-threatening conditions that may present in a similar way to an anaphylactic reaction include severe asthma and septic shock, for example due to meningococcal infection.
Non-life-threatening conditions that share some of the features of anaphylaxis are
- Simple faints—particularly, if they occur at the time of vaccination
- Hyperventilation and panic attacks—these can be particularly confusing in patients with a history of anaphylaxis who panic because they think that they might have been exposed to the allergen that provokes their anaphylaxis
- Breath-holding attacks in small children
- Urticaria or angio-oedema not associated with anaphylaxis
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Management of anaphylaxis |
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TOPAbstractAnaphylaxis and the GP...Causes of anaphylaxisFeaturesAirway, Breathing and...Differential diagnosisManagement of anaphylaxisCardiorespiratory arrest...Follow-upReferences |
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If suspected when the initial call for help comes in—call an emergency ambulance immediately, then visit. Ask when the initial call is taken if the patient has had a similar event before. If so, ask if he/she has an Epipen or similar. If the response is yes, advise the caller to use it immediately.
On arrival or if the event occurs in the surgery
Follow the algorithm in Fig. 3. Ensure that the patient is comfortable. Patients with airway and breathing problems may prefer to sit up as this will make breathing easier. Lying flat with or without leg elevation is helpful for patients with a low blood pressure, although the circulatory effects of anaphylaxis do not respond, or respond only transiently, to lying a patient flat. Pregnant patients should lie on their left side to prevent caval compression. If a patient feels faint, do not sit or stand him/her up as this may cause cardiac arrest. Patients who are breathing and unconscious should be placed in the recovery position.
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Every GP surgery should have an anaphylaxis kit, particularly if vaccinations are given in the surgery. The kit should be checked regularly to ensure that the drugs in it are in date. Two points are available through the Quality and Outcomes Framework (Medicines 2) for practices that possess the equipment and in-date emergency drugs to treat anaphylaxis.
Removing the trigger
Stop any drug suspected of causing an anaphylactic reaction. For example, if a patient is having an infusion of a gelatin solution or antibiotic, then stop the infusion. Remove the sting after a bee sting. If the anaphylaxis is food related, attempts to make the patient vomit are not recommended. Do not delay treatment if it is not possible to remove the trigger.
Adrenaline
Give intramuscular adrenaline as soon as possible to all patients with clinical signs of shock, airway swelling or breathing difficulty. If an adrenaline auto-injector is the only available adrenaline preparation, then use it. Otherwise, give 0.5 ml of 1 : 1000 adrenaline solution for an adult or child over the age of 12, half the adult dose for a child aged 6–12 years, a quarter of the adult dose for children aged between 6 months and 6 years, and 0.05 ml for a baby under 6 months old. The preferred point of intramuscular injection is the midpoint of the anterolateral thigh. Repeat the dose of adrenaline after 5 minutes; if improvement is transient, there is no improvement or there is deterioration after initial treatment. It may be necessary to give several doses of adrenaline.
Once the initial dose of adrenaline has been administered, monitor the patient's airway closely. In addition, monitor blood pressure, pulse oximetry and ECG if suitable equipment is available.
Oxygen and fluids
As soon as possible, give oxygen at a high flow rate (at least 10 l/minute) using a mask with an oxygen reservoir. Also give an intravenous fluid challenge, but do not delay administration of adrenaline while trying to gain IV access for fluid administration. Hartmann's solution or 0.9% saline are suitable fluids for initial resuscitation.
For an adult, give 500 ml–1 l of crystalloid or colloid fluid as rapidly as possible. Children should only be given crystalloid fluid. Give 20 ml/kg as rapidly as possible. If you do not know the child's weight, use a recent weight from the parent-held record if that is available. Otherwise, for children over a year old, weight is approximately twice the child's age plus 4 kg. Monitor the patient's response to the fluid challenge, and give further fluid challenges as needed.
Note: Consider colloid infusion as a cause of anaphylaxis and stop the infusion, if the patient was receiving a colloid infusion at the time that the symptoms of anaphylaxis started.
Antihistamines
The evidence to support the use of antihistamines in treatment of anaphylaxis is weak. Use chlorphenamine as second line agent only once adrenaline, together with oxygen and fluids if available, has been administered. Chlorphenamine should be given as an intramuscular or slow intravenous injection. Dose depends on age. Children over the age of 12 and adults should have the full dose of 10 mg, children aged 6–12 years require a half dose of 5 mg, and children between the ages of 6 months and 6 years should be given quarter of the adult dose (2.5 mg). Children aged under 6 months should receive a dose of 250 mcg/kg.
Steroids
Corticosteroids may help prevent or shorten protracted reactions. Give hydrocortisone intramuscularly, or by slow intravenous injection, as a second line agent, only once adrenaline, and oxygen and fluids if available, have been administered. Take care to avoid inducing further hypotension when giving hydrocortisone by the intravenous route. Dose of hydrocortisone depends on age. Give adults and children over 12 years, 200 mg of hydrocortisone. Halve the dose to 100 mg for children aged 6–12 years and use a quarter of the adult dose for children aged from 6 months to 6 years. For children under 6 months of age give 25 mg of hydrocortisone.
Bronchodilators
Consider adding bronchodilator treatment with inhaled or nebulized salbutamol and/or ipratropium to alleviate bronchospasm and wheeze.
Hospital admission
Patients who have had a suspected anaphylactic reaction (i.e. an airway, breathing or circulation problem-ABC-problem) should be treated and then observed for at least 6 hours in a clinical area with facilities for treating life-threatening ABC problems, even if they are well. In practice, this means admission to hospital or observation in A&E. This is because up to 20% of patients who have an anaphylactic reaction have a biphasic reaction with further symptoms appearing 4–10 hours after the initial reaction.
All patients should be reviewed by a senior clinician prior to discharge. In some cases, it may be appropriate for patients to be prescribed antihistamines and oral steroid therapy for up to 3 days to decrease the chance of further reaction or to alleviate the symptoms of urticaria.
Reporting of anaphylactic reactions
Adverse drug reactions that include an anaphylactic reaction should be reported to the Medicines and Healthcare products Regulatory Agency using the yellow card scheme (www.mhra.gov.uk). The British National Formulary includes copies of the Yellow Card at the back of each edition. Discuss all cases of fatal anaphylactic reaction with the coroner.
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Cardiorespiratory arrest following an anaphylactic reaction |
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TOPAbstractAnaphylaxis and the GP...Causes of anaphylaxisFeaturesAirway, Breathing and...Differential diagnosisManagement of anaphylaxisCardiorespiratory arrest...Follow-upReferences |
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Start cardiopulmonary resuscitation immediately and follow current resuscitation guidelines (see page 338). Use doses of adrenaline recommended in the resuscitation guidelines. The intramuscular route for adrenaline is not recommended after cardiac arrest has occurred.
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Follow-up |
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TOPAbstractAnaphylaxis and the GP...Causes of anaphylaxisFeaturesAirway, Breathing and...Differential diagnosisManagement of anaphylaxisCardiorespiratory arrest...Follow-upReferences |
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All patients presenting with anaphylaxis should be referred to an allergy clinic to identify the cause, and thereby reduce the risk of future reactions and prepare the patient to manage future episodes themselves. There is a list of specialist clinics on the British Society for Allergy and Clinical Immunology website (www.bsaci.org).
Adrenaline auto-injectors
The risk of an individual suffering recurrent anaphylactic reaction is roughly 1 in 12 per year. Consider providing an adrenaline auto-injector device to patients with idiopathic anaphylaxis or those with triggers that are difficult to avoid, such as stings or food-induced reactions. Patients or bystanders may then use the device to deliver a rapid dose of adrenaline as first aid at the first signs of any further episode of anaphylaxis. An auto-injector is not usually necessary for patients who have suffered drug-induced anaphylaxis, unless it is difficult to avoid the drug. Patients taking tricyclic antidepressants or monoamine oxidase inhibitors, cocaine users, and patients with ischaemic heart disease or uncontrolled hypertension are more at risk of adverse effects of adrenaline. Consider seeking specialist advice before prescribing an auto-injector to these patients.
Two adrenaline auto-injector devices are available in the UK at present, the Epipen and the Anapen. Both come in adult (300 mcg) and paediatric doses (150 mcg) and are available on NHS prescription. Ensure that an adequate supply is provided to treat symptoms until medical assistance is available and that enough devices are prescribed so that a device is available for use in each of the locations that the patient is most likely to be in (for example, one at home, one in the car and one at work or at school). Most patients will require more than one device.
Auto-injector devices consist of a fully assembled syringe and needle. Injection should only be given into the anterolateral aspect of the mid-thigh and can be given through clothing if needed. Patients and others likely to be with the patient should be taught how to use the device that is prescribed. Precise directions on how to administer the Epipen and Anapen differ and are given on the manufacturers’ websites (www.epipen.co.uk and www.anapen.co.uk, respectively). Both manufacturers produce dummy pens that can be purchased and used for training purposes. In addition, packs should be labelled so that, in the case of rapid collapse, someone else is able to administer the adrenaline.
Patients should also be instructed about the care of their auto-injector devices. Adrenaline can be affected by heat and direct sunlight. Auto-injector devices should be stored away from any extremes of temperature in their original packaging. They should not be refrigerated. The condition of the adrenaline should be periodically checked through the observation ‘window’ on the device. If the adrenaline has become cloudy or discoloured, the device should be discarded and replaced. Auto-injection devices also have a limited shelf life. Both the adult and paediatric Epipen and the adult Anapen have a shelf life of 2 years from the date of manufacture. The paediatric Anapen has a shelf life of 21 months from the date of manufacture. Patients should be instructed to note the expiry date of their devices when they are received and ensure that they order replacements in good time.
Advise patients to seek urgent medical assistance when experiencing anaphylaxis and after using an adrenaline auto-injector. Auto-injectors should be replaced as soon as possible after use.
Note: Adrenaline can fail to reverse the clinical manifestation of an anaphylactic reaction, especially when its use is delayed or in patients treated with beta blockers. The decision to prescribe a beta blocker to a patient at increased risk of an anaphylactic reaction should be made only after assessment by an allergy specialist and cardiologist.
Education and support
After an episode of anaphylaxis, warn patients or parents about the possibility of recurrence. Discuss with them the importance of allergen avoidance if the allergen is known and ways to minimize risk. For example, if the allergen is a food, patients need to know what products are likely to contain it and any alternative names for the substance that might be used on packaging. There is evidence that individualized action plans for self-management decrease risk of recurrence. Advise sufferers to wear a device, such as a Medic-Alert bracelet or Medi-Tag (Box 1), that will alert bystanders or medical staff should a further attack occur.
| Box 1. Obtaining Medic-Alert jewellery or a Medi-Tag Medic-Alert, Tel: 0800 581 420, website: www.medicalert.org.uk Medi-Tag, Tel: 0121 212 3636, website: www.hoopers.org/meditag.asp Information and support for patients and carers Allergy UK, Tel: 01322 619898, website: www.allergyuk.org Anaphylaxis Campaign, Tel: 01252 542029, website: www.anaphylaxis.org.uk
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At each review, ensure that patients and carers know the early signs of anaphylaxis that they should watch out for in order that they can summon urgent medical assistance and use emergency medication. Check that they know how to use any medication or devices that have been prescribed. If the patient has an auto-injection device, recommend practice with a dummy device so that everyone knows what to do in an emergency. Direct patients to sources of self-help information (Box 1). For schools attended by children at risk of severe allergic reactions, specific guidance and training is available from website www.allergyinschools.org.uk.
Severe allergic reactions are very frightening both for the patient and for those that witness the attack. Exploration of anxieties and fears and provision of a clear management plan that the patient and/or carer understands can go a long way to allay those anxieties and reduce psychological distress.
Key points
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References |
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TOPAbstractAnaphylaxis and the GP...Causes of anaphylaxisFeaturesAirway, Breathing and...Differential diagnosisManagement of anaphylaxisCardiorespiratory arrest...Follow-upReferences |
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Pumphrey RSH. Fatal anaphylaxis in the UK, 1992-2001. In: In: Anaphylaxis (Novartis Foundation Symposium 257) (2004) Wiley, UK. pp.116–132. ISBN: 9780470861141.
Resuscitation Council UK. Emergency medical treatment of anaphylactic reactions: guidelines for healthcare providers. (2008) Accessed via www.resus.org.uk/pages/reaction.pdf [date last accessed 30.3.2008].
Simon C, Everitt H, van Dorp F, Jenkins G, Schroeder K. Oxford Handbook of General Practice. (3rd Edition). Oxford: Oxford University Press. (In preparation).
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