Page 471 - Clinical Small Animal Internal Medicine

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and X, so factor VII depletion results in the initial clotting Patients experiencing clinical bleeding secondary to
VetBooks.ir test abnormalities detected in animals with anticoagu- vitamin K antagonists should be treated with fresh
frozen plasma (FFP) transfusion in addition to paren-
lant rodenticide ingestion. However, significant hemor-
rhage does not begin until factor II depletion occurs
Patients who may have ingested ethylene glycol (EG)
3–4 days after toxin ingestion. Diagnosing anticoagu- teral vitamin K1 administration.
lant rodenticide toxicity in the initial 3–4 days following present a unique clinical challenge due to the extremely
exposure allows for successful treatment prior to major time‐sensitive and dangerous nature of this toxicity. Cats
bleeding. exposed to EG less than three hours prior to presen-
Many patients present for veterinary care very shortly tation (and dogs exposed less than eight hours prior to
(e.g., one hour) after ingestion of anticoagulant rodenticide. presentation) must be aggressively tested and/or treated.
Unless a concurrent disorder of hemostasis is suspected The presence of EG can be proven by blood tests, but
or clinical bleeding is present, coagulation testing is available tests are imperfect. Bedside tests include the
unnecessary in these patients as long as the client is Kacey Ethylene Glycol Test Strips (Kacey Inc., Asheville,
absolutely certain that exposure occurred recently (e.g., NC) and the Catachem VetSpec Ethylene Glycol
within the past few hours). If exposure has occurred Qualitative Test Kit (Catachem Inc., Oxford, CT). These
more than 24 hours prior to presentation, or if timing of tests are subjective and based on visual determination of
exposure is unknown, diagnostic testing is indicated. color change, and the presence of other substances such
Common testing recommended for anticoagulant roden- as proplylene glycol or ethanol may cause false‐positive
ticide toxicity includes packed cell volume (PCV), total test results. The results of two small studies led to some
solids (TS), and clotting times (PT and aPTT). Activated concern regarding the sensitivity and specificity of these
clotting time (ACT) can be tested if PT and aPTT are tests. One study evaluating the Kacey Ethylene Glycol
unavailable. PT prolongation, which usually occurs Test Strips published in 2008 reported a sensitivity of
48 hours after ingestion, occurs prior to aPTT prolonga- only 56–67% for detection of 20 mg/dL EG (a potentially
tion due to the short half‐life of factor VII (6.2 hours) lethal dose for cats) in blood. This study also reported a
compared with factor II, IX, and X. aPTT prolongation specificity of 25–50% for detection of 80 mg/dL EG in
is typically seen after depletion of factor IX, whose half‐ blood. The authors of the study concluded that the test
life is 13.9 hours. Prolongation of both PT and aPTT is should not be used as a sole determinant of intoxication
expected prior to significant clinical bleeding following due to the risk of both false‐positive and false‐negative
anticoagulant rodenticide exposure. These different test results.
results at various time points after ingestion of antico- The results of a second study were published in 2014 in
agulant rodenticide highlight the critical importance of the Journal of Veterinary Emergency and Critical Care.
establishing a timeline of exposure whenever possible. This study compared the Kacey Ethylene Glycol Test to
The “proteins induced by vitamin K antagonism” (PIVKA) the Catachem VetSpec Etylene Glycol Qualitative Test
test and specific blood tests for anticoagulant rodenticide Kit. EG was added to canine blood at concentrations
levels are typically not useful in the acute diagnosis and ranging from 0 to 100 mg/dL, and 30 samples were eval-
treatment of the routine small animal patient with antico- uated separately by two individuals. The tests were
agulant rodenticide ingestion because plasma samples assigned a score of less than 20 mg/dL, 20–50 mg/dL, or
must be sent to a diagnostic lab and there is delay in test greater than 50 mg/dL. Sensitivity and specificity were
results. These tests may be indicated when anticoagulant 100% for the Kacey test, with good agreement between
rodenticide toxicity is suspected but the patient has no two readers. In this study the VetSpec test performed
known exposure; however, samples must be collected less well. Sensitivity and specificity were only 65%
prior to treatment, and the clinician must proceed with and 70% respectively for one reader and 95% and 40% for
treatment before test results are available. the other.
Treatment for a patient exposed to anticoagulant A separate publication evaluated an EG test kit
rodenticide invariably involves enteral or parenteral designed for use on a chemistry analyzer found in major
vitamin K1 therapy, but the timeline of exposure and clinical pathology laboratories (the Hitachi P‐modular
symptoms dictates the specific therapeutic plan for each 800 chemistry analyzer). This test was found to accu-
patient. Vitamin K1 (2.5–5 mg/kg/day IM, SC, or PO for rately measure blood EG, and results were not signifi-
up to six weeks) can be started orally in the asympto- cantly altered by the presence of propylene glycol.
matic patient with recent exposure (<48 hours ago). Although the development and assessment of new
If more than 48 hours have passed since exposure and tests continue, most veterinary hospitals do not, at this
coagulation tests are prolonged, but clinical bleeding is time, have a reliably sensitive and specific way to meas-
not observed, a single dose of parenteral vitamin K1 ure blood EG levels. Woods’ lamp evaluation of the oral
can be given prior to starting oral vitamin K1 therapy. cavity, face, vomitus, and urine can provide evidence of