Lab 3: changes in haemostasis

Question 1

list the three groups of haemostasis disorders?

Answer 1

1. vasculopathy
2. thrombocytopathy
3. coagulopathy

Question 2

what is a vasculopathy?

Answer 2

decreased ability of vasoconstriction in the case of vessel injury

Question 3

what is a thrombocytopathy?

Answer 3

decreased ability of platelets to aggregate and adhere to the site of injury

Question 4

what is a coagulopathy?

Answer 4

problems with the intrinsic, extrinsic and common pathways of the coagulation cascade

Question 5

list the tests for coagulopathies?

Answer 5

• appearance of first fibrin strand (clotting time)
• appearance of clot (clotting time on different surfaces)
  
  • watch glass
  • plastic syringe
  • glass tube
  • ACT tube
• clot retraction time
• Prothrombin time (PT)
• Activated partial thromboplastin time (APTT)
• thrombin time (TT)

Question 6

list the tests for thrombocytopathies?

Answer 6

• signs of increased bleeding tendency
• BMBT (buccal mucosal bleed time)
• platelet aggregation test

Question 7

list the methods for producing a platelet count?

Answer 7

1. measuring using a haemocytometer
   
   • number of platelets in 10 rectangles
   • multiply number by x10-9
2. estimation using a blood smear
   
   • 1 platelet means 20 x10-9/l
   • can evaluate aggregation
3. using an automatic cell counter
   
   • volumetric impedance method

Question 8

general platelet count?

Answer 8

200-800 x10-9

Question 9

major causes of thrombocytopenia?

Answer 9

1.decreased production in the bone marrow
- due to parvovirus, or heavy metal poisoning etc.
2. increased utilisation
- DIC
3. increased destruction
- autoimmune thrombocytopenias
- pancreatitis etc.
4. due to sequestration
- splenomegaly
5. loss of thrombocytes
- sub acute bleeding - not chronic as bone marrow will
have time to replenish lost platelets

Question 10

how would we perform a platelet aggregation test?

Answer 10

• use an aggrometer to estimate the aggregating ability of platelets
• add ADP or epinephrine to induce aggregation which will cause the fluid in the curvette to become clear
• use a spectrometer to record the process

Question 11

describe the thrombocyte morphology?

Answer 11

diameter: 1-2 micrometers
horse, sheep, and cattle have the smallest
cats have the biggest
bird platelets are nucleated

Question 12

list the main causes of thrombocytopathies?

Answer 12

1. improper platelet development - hereditary,
   glycoprotein deficiencies etc.
2. Von williebrands disease
3. uraemia, liver failure, myelo- and/orlymphoproliferative
   disease, non-steroidal anti-inflammatory drugs

Question 13

features of dicumarol toxicosis?

Answer 13

• in early stage only PT is increased, later APTT is increased
• competitive antagonist of vit. K
• vit. K deficiency causes inability of factors VII, IX, X, II
• factor VII has the shortest half life - PT is increased when there is a factor VII deficiency, so this test will show problem first

Question 14

what is the most accurate way to detect fibrinolysis?

Answer 14

the examination of the D-dimer level in the blood

- it is produced from fibrin only

Question 15

what is DIC?

Answer 15

• disseminated intravascular coagulopathy
• common acute disorder
• secondary disorder caused by primary diseases such as septicaemia, pancreatitis, widespread burns or necrosis by large tumours etc.
• microthrombus formation and fibrinolysis are present around the body due to severe tissue damage or necrosis
• coagulation factors and platelets are consumed rapidly

Question 16

how to test for DIC?

Answer 16

• latex agglutination method

Question 17

what is von Willebrand’s disease?

Answer 17

• hereditary, doberman types
• factor VIII is deficient
• dogs with disease have increased BT, BMBT, decreases clot retraction ability and sometimes coagulation disorders

Question 18

how would you diagnose Von Willebrand’s disease?

Answer 18

based on the detection of the lack of Von Willebrand related antigen