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.
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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)