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JULY/AUGUST 2017
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TVPJOURNAL.COM
CONTINUING
EDUCATION
Anaphylactic Shock: How to
Effectively Diagnose and Treat
Jennifer L. Lyons, MS, and Jordan R. Scherk, DVM, DACVECC
Blue Pearl Veterinary Partners, Midvale, Utah
Anaphylaxis is defined as the acute onset of a
hypersensitivity reaction causing the release
of mediators from mast cells and basophils.
Anaphylaxis may be a life-threatening condition
that can involve one or more organ systems.
Often, a specific cause for anaphylaxis is not
known. Anaphylaxis may be brought on by
anaphylactic or anaphylactoid reactions; treatment
is the same regardless of reaction type.
1,2
Veterinarians are seeing an increasing number
of anaphylaxis patients because of the range
of substances patients are exposed to, such as
vaccines, new medications, and those from
outdoor physical exposures
3
(see Specific Causes
of Anaphylaxis ). However, anaphylaxis is
often misdiagnosed because definitive criteria
to distinguish anaphylaxis from an allergic
reaction are lacking.
10
This article reviews
anaphylaxis pathophysiology, diagnostic
criteria, treatment, and clinical examples.
PATHOPHYSIOLOGY
Anaphylactic reactions are classified into 4
separate categories: type I, or immunologic
IgE mediated; types II and III, which
are immunologic IgE independent; and
type IV, or nonimmunologic. Most
anaphylaxis patients are likely to have
type I reactions, but it is unclear why.
2
Anaphylactic Reaction:
Immunologic IgE Mediated
In immunologic IgE-mediated reactions,
patients do not show clinical signs at the
initial allergen exposure. Upon reexposure,
IgE antibodies are produced, and the
allergen forms a "bridge" that cross-
links these antibodies via a high-affinity
receptor, FcεRI, located in the membrane
of mast cells and basophils. After binding,
shutterstock.com/Irina Kozorog
CONTINUING EDUCATION
BEES POSE AN ANAPHYLACTIC THREAT because
the venom in their stings contains peptide 401,
phospholipase A2, melittin, and hyaluronidase.