Anaphylaxis is primarily a clinical diagnosis. Recognising anaphylaxis can sometimes be problematic, for example, in the absence of an obvious trigger. In addition, skin and mucosal features can be absent in up to 10–20% of episodes.6 Serial serum tryptase levels can sometimes assist in confirming anaphylaxis in unclear cases.5,6 Anaphylaxis should be considered in any patient acute respiratory distress, bronchospasm, hypotension and/or cardiac arrest (Table 1).5 Show
EpidemiologyInternationally, lifetime prevalence of anaphylaxis has been estimated to be 0.05–2.0%.7 In Australia, anaphylaxis presentations are increasing (Figure 1).8 However, deaths from anaphylaxis remain relatively rare, with 112 (mostly adult) identified deaths between 1997–2005 (Figure 2).8 Figure 1. Time trends in anaphylaxis admissions in Australia, 1994–2005 Figure 2. Causes of anaphylaxis fatalities by age group, Australia 1997–2005 Causes of anaphylaxisMedications, food and insect venom are the most common triggers for anaphylaxis. Medications are a common trigger for anaphylaxis hospitalisation in older adults (Figure 3), and disproportionately contribute to anaphylaxis deaths in Australia (57%) (Figure 2).8 Medications that most commonly trigger anaphylaxis are antibiotics (especially penicillins), anaesthetic drugs, non-steroidal anti-inflammatory drugs (NSAIDs) and opiates.9 Figure 3. Causes of anaphylaxis admissions by age group, Australia 1994–2005 Food is the most common trigger for anaphylaxis in children.4 Hospitalisation for food-related anaphylaxis is most common in the 0–4 years age group in Australia, with a second peak in the 15–29 years age group (Figure 3).8 Overall, food allergies caused only 6% (n=7) of all anaphylaxis deaths between 1997–2005, six of whom were aged more than 10 years (Figure 2).8 The foods that most commonly trigger anaphylaxis are peanuts, tree nuts, hen’s eggs, cow’s milk, wheat, shellfish, fish and seeds (eg. sesame).10 Nut allergies carry the highest risk of anaphylaxis and death from anaphylaxis.4,10,11 The venom of bees, wasps, and certain types of ants can trigger anaphylaxis. Insect stings were associated with 18% (n=20) of anaphylaxis deaths between 1997–2005, mostly in males aged more than 35 years (Figure 2).8 Australia-wide data regarding insect sting related anaphylaxis presentations and hospital admissions remain limited.8 Note that exercise-induced anaphylaxis can occur in association with a food trigger or in isolation.6 Other less common triggers of anaphylaxis such as latex, radiocontrast media and idiopathic anaphylaxis will not be specifically addressed here. Risk factorsRisk factors for developing anaphylaxisSome features in a patient’s medical history may indicate an increased risk of anaphylaxis, including previous anaphylaxis, multiple drug allergies, nut allergy and a history of asthma (especially if poorly controlled).10,12,13 In addition, certain factors present around the time of allergen exposure can increase the risk of anaphylaxis. These include alcohol, exercise, NSAID use and intercurrent infection.5,6,11,14 There are currently no tests that predict anaphylaxis risk.15 While predictive for clinical allergy, the level of allergen specific IgE or size of the skin prick testing (SPT) reaction do not correlate with risk of anaphylaxis.3,6 Risk factors for increased severity or fatalityA number of factors influence the risk of fatal anaphylaxis, including the severity of underlying allergy, allergen dose, patient age, medical comorbidities and concurrent medication use.6,11 Asthma and cardiovascular disease in particular are associated with an increased risk of severe or fatal anaphylaxis.6,10,11,14 The use of concurrent medications, such as beta-blockers and angiotensin converting enzyme inhibitors (ACEIs), can also increase the severity of anaphylaxis and/or render anaphylaxis more refractory to treatment.6,11,15 Risk factors for fatality vary according to the cause of anaphylaxis (Table 2). Table 2. Risk factors for fatal anaphylaxis by trigger
ManagementAcute managementAdrenaline is first line treatment for anaphylaxis.16 Table 3 outlines the emergency management of anaphylaxis. Intramuscular (IM) injection into the anterolateral thigh is the preferred route for the initial administration of adrenaline (Table 4).10 Additional supportive therapy with nebulised beta-2 agonists (for bronchospasm), H1 antihistamines (for cutaneous symptoms), and/or glucocorticoids (may reduce the risk of biphasic reactions) is often utilised in clinical practice, but plays a less important role and is considered second line.6,10,17 These medications should never be used as an alternative to, or before, adrenaline for anaphylaxis.15 Table 3. Emergency management of anaphylaxis
Long-term managementGeneral practitioners play a central role in the long-term management of patients with anaphylaxis. Long-term management includes the following steps.1 Referral to an allergy specialistAll patients with anaphylaxis should be referred to an allergy specialist (allergist/clinical immunologist) for further assessment and evaluation.1 Identification of trigger(s)Accurate identification of the causative allergen guides appropriate management and enables future avoidance. History taking should cover recent medication use (including complementary medicines), food intake and/or insect stings, as well as any relevant co-factors. Following this, SPT and/or blood allergen specific IgE (sIgE) testing to the suspected allergen may be indicated.18 Tests should be interpreted using standardised criteria. For SPT, appropriate safety precautions should be in place. Screening SPT and sIgE testing (in the absence of a history of allergic reaction and identification of an implicated allergen) is discouraged. Where no triggers are identified on history together with negative SPT or blood sIgE testing, a diagnosis of idiopathic anaphylaxis may be considered, but this is less common.6 Avoidance of trigger(s)Avoidance of allergens is essential to minimise risk. Allergen-specific strategies are outlined below. Medications
Food
Insect stings
Prescription of adrenaline autoinjectorPatients should be assessed for the need for an adrenaline autoinjector (EpiPen® or Anapen®). All patients who have experienced an anaphylactic reaction and have continuing risk of exposure to an allergen trigger should be prescribed an adrenaline autoinjector. For example, those with food or insect related anaphylaxis usually require an adrenaline autoinjector, whereas those with medication related anaphylaxis are not commonly prescribed an adrenaline autoinjector as the trigger can be more easily avoided. Prescribing guidelines can be found at www.allergy.org.au (see Resources). Provision of an adrenaline autoinjector must be accompanied by education for patients and carers about when and how to use the device, and provision of an anaphylaxis action plan (see next step). The Pharmaceutical Benefits Scheme allows for Authority prescriptions of adrenaline autoinjectors (maximum quantity of two with no repeats). Approval is provided for individuals assessed as being at significant risk of anaphylaxis (with the name of the consulting clinical immunologist, allergist, paediatrician or respiratory physician) and patients who have received adrenaline for treatment of anaphylaxis.1 Written emergency action plan for anaphylaxisAll patients who have had anaphylaxis and remain at risk of further allergic reactions should have a personalised emergency action plan that outlines the emergency management of allergic reactions. Patients who have been prescribed an adrenaline autoinjector should have a personalised emergency action plan for anaphylaxis (see Resources). This plan should be specific to the prescribed adrenaline autoinjector (Epipen® or Anapen®). (Note: patients who have experienced a mild to moderate allergic reaction but not anaphylaxis and who do not have an adrenaline autoinjector should also be provided with an emergency action plan for allergic reactions The written emergency action plan for anaphylaxis should include:
Regular follow upAnnual review with a regular family doctor is an important aspect of ongoing care. At the annual visit, the GP should:
Repeat follow up with an allergy specialist may be considered if new symptoms develop, confirmation of allergy resolution is required, allergies are difficult to manage and/or during periods of increased risk. Relevant periods of increased risk may include adolescence, leaving home or travel, and changes in health status and comorbidities. The specialist may suggest additional tests or management strategies as appropriate. Key points
Resources
Competing interests: None. What are the priority interventions for anaphylaxis?Treatment of anaphylactic shock include:. Remove antigen. Removing the causative antigen such as discontinuing an antibiotic agent could stop the progression of shock.. Administer medications. ... . Cardiopulmonary resuscitation. ... . Endotracheal intubation. ... . Intravenous therapy.. Which of the following interventions is the single most important aspect for a patient at risk for anaphylaxis?Epinephrine — Epinephrine is the first and most important treatment for anaphylaxis, and it should be administered as soon as anaphylaxis is recognized to prevent the progression to life-threatening symptoms as described in the rapid overviews of the emergency management of anaphylaxis in adults (table 1) and children ...
How can you reduce the risk of anaphylaxis?The best way to prevent anaphylaxis is to stay away from substances that cause this severe reaction. Also: Wear a medical alert necklace or bracelet to indicate you have an allergy to specific drugs or other substances. Keep an emergency kit with prescribed medications available at all times.
What are the risk factors of anaphylaxis?Risk factors for severe anaphylaxis and anaphylactic shock include: a previous anaphylactic reaction. allergies or asthma.. certain medications such as penicillin.. insect stings.. foods such as: tree nuts. shellfish. milk. eggs. agents used in immunotherapy. latex.. |