Haematopoietic - Bleeding Disorders

Question 1

What is a bleeding disorder?

Answer 1

Abnormal condition which allows blood to escape from injured vessels or interferes
with haemostasis following injury

Question 2

What does primary haemostasis involve?

Answer 2

reflex constriction of the blood vessel and the formation of a platelet plug

Question 3

What does secondary haemostasis involve?

Answer 3

consists of stabilisation of this platelet plug by fibrin, which results from activation of the clotting cascade

Question 4

what is Von Willebrand’s disease?

Answer 4

deficiency of von willebrands factors

Question 5

what breed is mostly affected by Von Willebrand’s disease?

Answer 5

dobermans due to lack of manufacturing this protein

Question 6

what does secondary haemostasis result in?

Answer 6

fibrin formation

Question 7

what is fibrin?

Answer 7

a protein that scaffolds the platelets and stabilises/anchors the primary platelet plug

Question 8

what are clotting factors?

Answer 8

enzymes which catalyse a cascade of reactions that breakdown of proteins to make active form Fibrin from fibrinogen

Question 9

what are the two arms that cascade?

Answer 9

extrinsic and intrinsic

Question 10

what do the extrinsic and intrinsic pathways do?

Answer 10

They come together into a common pathway for the later stage where prothrombin is converted to thrombin which catalyses fibrinogen in to fibrin

Question 11

which arm of the clotting cascade isaffected by vitamin k deficiency?

Answer 11

extrinsic

Question 12

what do cats
that aren’t eating or cats with a problem with fat digestion because of blocked bile ducts have?

Answer 12

clotting disorders

Question 13

what is primary haemostasis effecting?

Answer 13

• Platelets - decreased number (thrombocytopenia) and decreased function
• Vessels - vasculitis

Question 14

what is secondary haemostasis effecting?

Answer 14

Quantitative disorders - decreased amount clotting factors
Qualitative disorders - decreased function clotting factors

Question 15

how are primary haemostatic disorders characterised?

Answer 15

multiple minor bleeds

Question 16

how are secondary disorders characterised?

Answer 16

single large bleeds and rebleeding at the site of injury

Question 17

what are examples of primary bleeding disorders?

Answer 17

petechiae, ecchyotic haemorrhages, prolonged bleeding from cuts, surface bleeding, multiple sites of bleeding

Question 18

what are examples of secondary bleeding disorders?

Answer 18

haematomas, localised site of bleeding, delayed bleeding or rebleeding from cuts, deep and avity bleeds, epistaxis

Question 19

what is buccal mucosal bleeding time used for?

Answer 19

test platelet defects and vessel wall defects

Question 20

how do you carry out a buccal mucosal bleeding time test?

Answer 20

• This can usually be carried out in the conscious dog but in cats heavy sedation or general anaesthesia is required
• The patient is placed in lateral recumbency and the upper lip folded up and held in place with a gauze bandage tied around the muzzle or head
• This bandage should mildly obstruct venous return
• A pair of small standardised incisions are made in the buccal mucosa with a spring loaded bleeding time device
• Blood is blotted away using filter paper, without disturbing the incision sites
• The time taken for cessation of bleeding is recorded
• Normal BMBT = < 3 mins in cats and < 3.5 mins in dogs
• Tend to be sedated

Question 21

what is estimation of platelet count?

Answer 21

used for the identification of quantitative platelet disorders

Question 22

howdo you carry out a platelet count estimation?

Answer 22

• The blood sample should be first checked for any clots
• The smear should be wedged-shaped with a good monolayer of cells
• Under low power the smear is scanned for any platelet clumps which would influence the count obtained and, under oil immersion (x 100), the number of platelets per high power field are counted
• This is repeated for around ten fields so that an average platelet count per high power field is obtained
• Each platelet per high power field represents approximately 20 x 109/l platelets in the circulation

Question 23

what is activated clotting time used for?

Answer 23

evaluates the intrinsic and common pathways

Question 24

how do you caryr out activated clotting time test?

Answer 24

• First few drops of blood sampled are discarded in case of endothelial activation factors interfering with the test results
• 2 mls blood is collected into the test tube
• The test tube is gently inverted to mix and then left undisturbed for 40 seconds
• The tube is then inverted every 10 seconds and the time taken for complete clot formation recorded

Question 25

what does activated partial thromoplastin time test?

Answer 25

evaluates the intrinsic and common pathways

Question 26

what does prothrombin time test?

Answer 26

extrinsic and common pathways