Anaphylaxis

Allergy, Asthma & Clinical Immunology, Nov 2011

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.

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Anaphylaxis

Harold Kim 0 1 David Fischer 0 0 University of Western Ontario , London, Ontario , Canada 1 McMaster University , Hamilton, Ontario , Canada 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. - Introduction 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]. The more rapidly anaphylaxis develops, the more likely the reaction is to be severe and life-threatening [4]. Therefore, prompt recognition and management of the condition are imperative. However, anaphylaxis is often under-recognized and treated inadequately. Diagnosis and management are challenging since reactions are often immediate and unexpected. Furthermore, there is no single test to diagnose anaphylaxis in routine clinical practice [3,6]. This article will provide an overview of the causes and clinical features of anaphylaxis as well as strategies for the accurate diagnosis and management of the condition. Causes 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, cows 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. Co-morbidities and concurrent medications may also affect the severity of anaphylactic reactions and patient response to treatment. For example, patients with asthma and cardiovascular disease are more likely to experience a poor outcome from anaphylaxis. Concurrent administration of beta-blockers can interfere with the patients ability to respond to epinephrine, the firstline of treatment for anaphylaxis (discussed later). Furthermore, the use of angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) can impact a patients compensatory physiologic response to anaphylaxis, leading to more severe reactions [10]. Signs and symptoms Since anaphylaxis is a generalized reaction, a wide variety of clinical signs and symptoms involving the skin, Table 1 Causes of anaphylaxis 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) [11]. 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 [12]. 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 signs and symptoms of anaphylaxis typically develop within minutes after exposure to the offending Table 2 Signs and symptoms of anaphylaxis [6,11] antigen, but may occasionally occur as late as 1 hour post exposure. Sympto (...truncated)


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Harold Kim, David Fischer. Anaphylaxis, Allergy, Asthma & Clinical Immunology, 2011, pp. S6, 7, DOI: 10.1186/1710-1492-7-S1-S6