Page 1801 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

1270 PART 11: Special Problems in Critical Care

INTRODUCTION/DEFINITION EPIDEMIOLOGY

The traditional definition of anaphylaxis is “a systemic, immediate hyper- The true incidence and prevalence of anaphylaxis is currently not
sensitivity reaction caused by immunoglobulin E (IgE)–mediated immu- known because of a lack of any controlled studies. Underdiagnosis,
nologic release of mediators from mast cells and basophils.” The term underreporting, and miscoding are substantial obstacles preventing an
“anaphylactoid” reaction has been traditionally defined as a clinically similar accurate estimation. Table 128-1 summarizes the major studies of
6-8
event not mediated by IgE. More recently, the World Allergy Organization incidence and prevalence and their relevant findings. A recent expert
1,2
(WAO) has referred to anaphylaxis as a “severe, life-threatening, generalized panel concluded that the lifetime prevalence of anaphylaxis is about
or systemic hypersensitivity reaction.” It suggested that the term ‘‘anaphy- 0.05% to 2%. The same study reported that the incidence is approxi-
9
lactoid reaction’’ be eliminated, and that all episodes clinically similar to mately 50 to 2000 episodes per 100,000 person-years.
IgE-mediated reactions be called anaphylaxis. 3 Geographic locations, age, gender, route of administration of
The difficulty in determining the clinical manifestations that define antigen, and atopy have been found to influence the incidence of
an anaphylactic event was highlighted in a symposium sponsored by anaphylaxis. 10-13
the National Institute of Health and the Food Allergy and Asthma Anaphylaxis is more common in males until age 15 years and more
Network. This symposium was convened to define the clinical mani- common in females after age 15 years. This has been documented in sev-
4,5
festations of anaphylaxis required to establish a diagnosis. No true defi- eral studies. 13,14 The reason for such gender differences is not clear, but
nition, in the classic sense of the term, resulted from the deliberations probably relates to hormonal influences. Anaphylaxis is more frequent
of this group, but they did define a clear-cut constellation of signs and in adults than children for some agents: radiocontrast media, plasma
symptoms requiring the necessity for treatment with epinephrine. They expanders, and anesthetics.
formulated three clinical scenarios during which anaphylaxis was highly Camargo et al investigated the epidemiology of anaphylaxis using
12
likely as a cause of the event and thus epinephrine therapy mandated. the number of autoinjector epinephrine prescription filled in 50 states
These scenarios can be summarized briefly as follows: and Washington, DC. A strong north-south gradient was observed for
the prescription of autoinjectors in the United States, with the highest
1. Acute onset of an illness (minutes to several hours) with involvement rates found in New England. This finding persisted after all other vari-
of the skin, mucosal tissue, or both and at least one of the following: ables (eg, population demographic characteristics, number of health
a. Respiratory compromise care providers, prescriptions for other medications) were adjusted.
b. Reduced BP or associated symptoms of end-organ dysfunction The authors concluded that regional differences in the number of
2. Two or more of the following that occur rapidly after exposure to a automatic epinephrine injections prescribed may provide insight into
the pathogenesis (eg, the potential role of vitamin D deficiency) of
likely allergen for that patient (minutes to several hours): reactions experienced as an outpatient. In the United Kingdom, the
a. Involvement of the skin-mucosal tissue incidence may be higher for those living in rural areas compared to
b. Respiratory compromise urban areas. 11
The relationship between atopy and anaphylaxis is complex. The
c. Reduced BP or associated symptoms incidence of latex anaphylaxis is clearly increased in atopic individuals
15
d. Persistent gastrointestinal symptoms but the same is not true for penicillin, insulin, insect stings, and muscle
3. Reduced BP after exposure to known allergens for that patient relaxants. Atopic subjects appear to be predisposed to anaphylaxis, but
10
(minutes to several hours). only a minority of such atopic individuals will experience an event.

TABLE 128-1 Incidence and Prevalence of Anaphylaxis.
Author Year Description of study Findings
Yocum et al 177 1999 Rochester Epidemiology Project. During the years 1983-1987, the average annual incidence rate was
21/100,000 person-years, and the most common triggers were foods,
medications, and insect stings.
Simons et al 178 2002 Dispensing data for all injectable epinephrine formulations over 5 consecutive years. 0.95% had injectable epinephrine dispensed for out-of-hospital treatment.
Bohlke et al 179 2004 Large HMO in the United States, 1991-1997. The incidence rate was 10.5 anaphylactic episodes per 100,000 person-years.
Helbling et al 180 2004 Investigated anaphylaxis with circulatory symptoms during a 3-year period, Incidence rate of 7.9-9.6/100,000 person-years.
1996-1998, in Bern, Switzerland.
Lieberman et al 9 2006 Panel convened to review major epidemiologic studies of anaphylaxis. There was a frequency estimate of 50 to 2000 episodes/100,000 person-years
or a lifetime prevalence of 0.05% to 2%.
Poulos et al 181 2007 Data on hospital admissions for anaphylaxis were extracted for the periods There was a continuous increase by 8.8% per year in the incidence rate of
1993-1994 to 2004-2005, respectively. ED visits/hospitalizations for anaphylaxis.
Camargo et al 12 2007 State-by-state dispensing data (filled prescriptions, including refills) for epineph- Average was 5.71 Epi-pens per 1000 persons (range from 2.7 in Hawaii to
rine autoinjectors in 2004 in the United States. 11.8 in Massachusetts).
Decker et al 182 2008 Population-based incidence study from 1990-2000 in the Rochester Epidemiology Overall age- and sex-adjusted incidence rate of 49.8/100,000 persons; the
Project. annual incidence rate increased from 1990 to 2000.
Lin et al 183 2008 Characterization of anaphylaxis hospitalizations in New York state in patients During the study period, 1990-2006, the anaphylaxis hospitalization rate
<20 years of age. increased by more than fourfold.
Sheikh et al 184 2008 Recorded incidence and lifetime prevalence of anaphylaxis in England were Age/sex standardized incidence of anaphylaxis was 6.7/100,000 person-years
investigated by using QRESEARCH, a national aggregated primary health care in 2001 and increased by 19% to 7.9/100,000 person-years in 2005; lifetime
database containing the records of >9 million patients. age/sex standardized prevalence of anaphylaxis was 50/ 100,000 in 2001 and
increased by 51% to 71.5/100,000 in 2005.

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