Lecture 8 9/10/24

Question 1

Which aspects of signalment and history are important for evaluating bleeding disorders?

Answer 1

-hereditary vs acquired disorder
-hx of trauma or toxin exposure
-family hx

Question 2

What are the clinical signs seen with primary hemostasis disorders?

Answer 2

-small bleeds
-petechia
-mucosal bleeding

Question 3

What are the clinical signs seen with secondary hemostasis disorders?

Answer 3

-large bleeds
-hemoabdomen
-hemarthrosis

Question 4

What are the mechanisms of thrombocytopenia?

Answer 4

-artifact
-decreased production
-increased consumption
-destruction
-loss
-sequestration

Question 5

Which thrombocytopenia mechanisms, when severe, can result in bleeding?

Answer 5

-decreased production
-increased consumption
-destruction

Question 6

What are the most common causes of each thrombocytopenia mechanism?

Answer 6

-artifact: platelet clumping
-decreased production: bone marrow disease
-increased consumption: DIC, tick-borne disease
-destruction: immune-mediated thrombocytopenia
-loss: hemorrhage
-sequestration: splenomegaly, endotoxemia

Question 7

What are the characteristics of DIC?

Answer 7

-coagulation gone wrong
-secondary to underlying disease causing widespread release of tissue factor and activation of coagulation
-results in intravascular clot
-leads to depletion of platelets and coagulation factors
-can result from anything that causes extensive tissue injury or inflammation

Question 8

What are the pathophysiologic mechanisms involved in DIC and the associated lab abnormality?

Answer 8

-consumption of platelets: thrombocytopenia
-consumption of coagulation factors: prolonged PTT, PT, ACT and decreased fibrinogen
-consumption of coagulation inhibitors: decreased antithrombin
-excessive fibrinolysis: increased D-dimers
-RBC shearing within intravascular clots: schistocytes on blood smear

Question 9

What are the mechanisms behind hemostatic problems arising from liver insufficiency?

Answer 9

-decreased production of coagulation proteins
-decreased clearance of fibrinolytic products

Question 10

Which coagulation factors require vitamin K for production?

Answer 10

-Factor 2
-Factor 7
-Factor 9
-Factor 10

Question 11

Which coagulation factor has the shortest half-life, thus depleting first when there is a vitamin K deficiency?

Answer 11

Factor 7

Question 12

What can cause vitamin K antagonism or deficiency?

Answer 12

antagonism:
-anticoagulant rodenticides
-moldy sweet clover
-moldy sweet vernal grass
deficiency:
-fat malabsorption

Question 13

What are the characteristics of protein-losing nephropathy?

Answer 13

-kidney disease/damage results in damage to glomerular filtration barrier
-results in urinary losses of proteins, especially albumin and antithrombin

Question 14

What level of antithrombin must a patient have to be at risk of increased thrombosis?

Answer 14

<50% of normal

Question 15

What are the characteristics of von Willebrand disease?

Answer 15

-hereditary
-uncommon
-mostly seen in dogs
-quantitative disorder: produce some, not enough
-bleeding of variable severity

Question 16

What are the characteristics of vWF antigen testing?

Answer 16

-reported as a percentage concentration in comparison with normal, pooled plasma
-carriers have <50% normal vWF
-those with clinical disease have <35% normal vWF

Question 17

What are the most common inherited single factor deficiencies?

Answer 17

-Factor 8 (hemophilia A)
-Factor 9 (hemophilia B)
-Factor 11 (hemophilia C)

Question 18

What are the characteristics of Factor 8 or Factor 9 deficiency?

Answer 18

-X linked
-no clinical bleeding unless factor activity is <20% of normal
-clinical signs of secondary hemostasis disorder
-diagnosis requires measurement of specific factor activities

Question 19

What are the characteristics of Factor 11 defeciency?

Answer 19

-autosomal
-mild to moderate bleeding tendencies in homozygotes
-heterozygotes are typically asymptomatic but may have a mildly prolonged PTT