Date Published: November 10, 2011
Publisher: BioMed Central
Author(s): Harold Kim, David Fischer.
Anaphylaxis is an acute, potentially fatal systemic reaction with varied mechanisms and clinical presentations. Although prompt recognition and treatment of anaphylaxis are imperative, both patients and healthcare professionals often fail to recognize and diagnose early signs and symptoms of the condition. Clinical manifestations vary widely, however, the most common signs are cutaneous symptoms, including angioedema, urticaria, erythema and pruritus. Immediate intramuscular administration of epinephrine into the lateral thigh is first-line therapy, even if the diagnosis is uncertain. The mainstays of long-term management include specialist assessment, avoidance measures, and the provision of an epinephrine auto-injector and an individualized anaphylaxis action plan. This article provides an overview of the causes, clinical features, diagnosis and acute and long-term management of this serious allergic reaction.
Anaphylaxis is defined as a serious allergic reaction that is rapid in onset and may cause death [1,2]. The prevalence of anaphylaxis is estimated to be as high as 2%, and appears to be rising, particularly in the younger age group [3-5].
Most episodes of anaphylaxis are triggered through an immunologic mechanism involving immunoglobulin E (IgE) which leads to mast cell and basophil activation and the subsequent release of inflammatory mediators such as histamine, leukotrienes, tryptase and prostaglandins. Although any substance has the potential to cause anaphylaxis, the most common causes of IgE-mediated anaphylaxis are: foods, particularly, peanuts, tree nuts, shellfish and fish, cow’s milk, eggs and wheat; medications (most commonly penicillin), and natural rubber latex. Exercise, aspirin, non-steroidal anti-inflammatory drugs (NSAIDs), opiates, and radiocontrast agents can also cause anaphylaxis, but anaphylactic reactions to these agents often result from non-IgE-mediated mechanisms. In other cases, the cause of anaphylactic reactions is unknown (idiopathic anaphylaxis). In children, anaphylaxis is most often caused by foods, while venom- and drug-induced anaphylaxis is more common in adults [4,7-9]. Table 1 provides a more comprehensive list of the potential causes of anaphylaxis.
Since anaphylaxis is a generalized reaction, a wide variety of clinical signs and symptoms involving the skin, gastrointestinal and respiratory tracts, and cardiovascular system can be observed (see Table 2). The most common clinical manifestations are cutaneous symptoms, including urticaria and angioedema, erythema (flushing), and pruritus (itching) . Patients also often describe an impending sense of death (angor animi). Death due to anaphylaxis usually occurs as a result of respiratory obstruction or cardiovascular collapse, or both. Evidence suggests that there is a direct correlation between the immediacy of symptom onset and the severity of the episode, with the more rapid the onset, the more severe the event . It is important to note that the signs and symptoms of anaphylaxis are unpredictable and may vary from patient to patient and from one reaction to another. Therefore, the absence of one or more of the common symptoms listed in Table 2 does not rule out anaphylaxis, and should not delay immediate treatment.
The diagnosis of anaphylaxis is based primarily on clinical signs and symptoms, as well as a detailed description of the acute episode, including antecedent activities and events. Diagnostic criteria for anaphylaxis were published by a multidisciplinary group of experts in 2005 and 2006, and are shown in Table 3[1,2]. A diagnosis of anaphylaxis is highly likely when any one of the criteria listed in Table 3 is fulfilled. Since the evaluation and diagnosis of anaphylaxis is often complex, referral to an allergist with training and expertise in the identification and management of anaphylaxis should be considered.
The mainstays of long-term management for patients who have experienced an anaphylactic episode include: specialist assessment, a prescription for an epinephrine auto-injector, patient and caregiver education on avoidance measures, and the provision of an individualized anaphylaxis action plan.
Anaphylaxis is an acute, potentially fatal systemic reaction with varied mechanisms and clinical presentations. Prompt recognition and treatment of anaphylaxis are imperative; however, both patients and healthcare professionals often fail to recognize and diagnose anaphylaxis in its early stages. Diagnostic criteria which take into account the variable clinical manifestations of anaphylaxis are now available and can assist healthcare providers in the early recognition of the condition. Immediate intramuscular administration of epinephrine into the lateral thigh is first-line therapy for anaphylaxis. Acute management may also involve oxygen therapy, intravenous fluids, and adjunctive therapies such as antihistamines or inhaled beta2-agonists. The mainstays of long-term management include specialist assessment, a prescription for an epinephrine auto-injector, patient and caregiver education on avoidance measures, and the provision of an individualized anaphylaxis action plan.
Dr. Harold Kim is the past president of the Canadian Network for Respiratory Care and co-chief editor of Allergy, Asthma &Clinical Immunology. He has received consulting fees and honoraria for continuing education from AstraZeneca, GlaxoSmithKline, Graceway Pharmaceuticals, King Pharma, Merck Frosst, Novartis, and Nycomed.