Page 523 - Problem-Based Feline Medicine

23 – THE BLEEDING CAT 515

● Half-life of factor XI post-transfusion is prob- Excessive bleeding after venepuncture, neutering
ably longer (2–3 days) than factor VIII or IX. and other surgical procedures.
● Cats with absolute factor XI deficiency may theo-
For cases with a defect not sufficiently severe to cause
retically become refractory to transfused factor IX
spontaneous hemorrhage, the age of detection will
because of antibody formation.
depend on the age when a procedure is performed.
Treatments in humans not evaluated in cats include Most cats are neutered at a young age, resulting in
lyophilized factor XI, recombinant factor VIIa, and detection of the defect at that time.
inhibitors of fibrinolysis (e.g. aminocaproic acid).
Signs due to anemia and local effects of hemorrhage
vary with severity of blood loss.
Prognosis
Some affected cats may not show spontaneous or
Prognosis is probably good for cats kept in an environ- excessive bleeding, also consistent with variable
ment that minimizes trauma and exuberant exercise. severity of the defect.
In one case a bleeding episode was suspected to have
Transmission been triggered by concurrent decreased platelet func-
tion associated with modified-live virus vaccination.
Transmission in cats is unknown. In humans, dogs and
cattle transmission is autosomal recessive.
Diagnosis
Prevention
Consistent signalment (young Devon Rex cats) and
As for hemophilia A, but testing for factor XI. signs of spontaneous or excessive bleeding are highly
suggestive.
VITAMIN-K RESPONSIVE COAGULOPATHY No evidence of other vitamin K related disorders.
IN THE DEVON REX ● No history of exposure to vitamin K antagonist poi-
sons.
Classical signs ● No clinical or laboratory evidence of liver disease.
● No diarrhea (exocrine pancreatic insufficiency and
● Spontaneous and excessive bleeding in
inflammatory bowel disease).
Devon Rex cats.
Hemostatic testing reveals normal platelet count and
BMBT (may rebleed), and prolonged PT, ACT and
Pathogenesis aPTT. PIVKA time has not been reported but is pre-
sumably prolonged.
Vitamin K is essential for carboxylation of clotting fac-
tors II, VII, IX and X. The uncarboxylated clotting fac- Quantification of vitamin K dependent factor activ-
tors cannot bind calcium, a necessary step in clot ities, using techniques similar to factor VIII quantifica-
formation (see Vitamin K antagonist rodenticides and tion in hemophilia A.
drugs).
Normalization of PT, ACT, aPTT and factor activities
The enzyme responsible for carboxylation has reduced with vitamin K therapy.
affinity for vitamin K, impairing its function.

Differential diagnosis
Clinical signs
Vitamin K antagonist rodenticide poisoning may be
Spontaneous bleeding in Devon Rex cats including ruled out in some cases on lack of exposure history.
hemothorax, intrapulmonary hemorrhage, hemarthrosis ● If exposure is possible, then the cat should be con-
and otic hemorrhages. Reported cases range from 5 fined in a rodenticide-free environment and treated
months to 2 almost years. with vitamin K for 6 weeks. After stopping