Friday, January 2, 2009

What is the Definition of Anaphylaxis?

Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death, It is considered highly likely when any 1 of the following 3 clinical criteria are fulfilled:

1. acute onset of an illness within minutes to hours, with involvement of the skin, or mucosal tissue, or both (e.g. generalized hives, pruritus or flushing, swollen lips, tongue, or uvula)
brochospasm, stridor, reduced peak expiratory flow, hypoxemia)
AND at least 1 of the following:
a) respiratory compromise (e.g. dyspnea, wheeze or)
b) reduced blood pressure or associated symptoms of end-organ dysfunction (e.g. hypotonia [collapse], syncope, incontinence);

2. two or more of the following that occur rapidly after exposure to a likely allergen for this patient (minutes to several hours):
a) skin or mucosal tissue involvement (e.g. generalized hives, itch or flush, swollen lips, tongue, or uvula)
b) respiratory compromise (e.g. dyspnea, wheeze or brochospasm, stridor, reduced peak flow, hypoxemia)
c) reduced blood pressure or associated symptoms (e.g. hypotonia [collapse], syncope, incontintence);
d) persistent gastrointestinal tract symptoms (e.g. crampy abdominal pain, vomiting)

3. reduced blood pressure after exposure to a known allergen for that patient (within minutes to hours)
a) Infants and children: low systolic blood pressure (age specific) or >30% decrease in systolic blood pressure
b) Adults: systolic blood pressure <90>30% decrease from that person's baseline.

Above definition is listed in Sampson HA, et al. J Allergy Clin Immunol 2006; 117:391-7. This is why patients at risk of anaphylaxis should: 1) try to identify the triggers as much as possible; 2) avoid the triggers or treat the triggers as much as possible; 3) always have a good backup plan, because Murphy's law happens ("If anything can go wrong, it will."); 4) include medications such as epinephrine by auto-injector, antihistamines, beta-agonist inhalers. These have been discussed in earlier blogs.

If you have questions about whether or not you have anaphylaxis OR what to do if you have an anaphylactic episode, ask your doctor...

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