L16: Primary Disorders of Haemostasis

Question 1

what is haemorrhage by rhexis

Answer 1

substantial tear in BV or heart chamber

Question 2

What is haemorrhage by diapedesis

Answer 2

escape of blood through a micro defect in a BV

Question 3

what is haematochezia

Answer 3

fresh blood in faeces

Question 4

what is dysentery

Answer 4

blood in diarrhoea

Question 5

what is melena

Answer 5

upper GIT haemorrhage leading to oxidised blood in stool

Question 6

what is hyphaema

Answer 6

haemorrhage at anterior chamber eye

Question 7

describe petechiae

Answer 7

pin point haemorrhages

Question 8

describe purpura

Answer 8

slightly larger than petechiae, >3mm

Question 9

describe ecchymoses

Answer 9

2-3cm, blotchy, irregular harmorrhages

Question 10

Describe suffuse haemorrhages

Answer 10

linear “paint brush” haemorrhages, especially over serosal/MM

Question 11

what is a haematoma

Answer 11

playable, discreet, space occupying mass of clotted blood

Question 12

Describe how haematomas age and assign colours to pigments

Answer 12

acute= red/blue (poorly oxygenated blood from veins)
–> blue-green (macrophages digs bilirubin, biliverdin)

Chronic= yellow as haemosidering deposited when macrophages digest iron +/- lipofuscin

Question 13

what factors determine the clinical significance of a haemorrhage ?

Answer 13

location (tissues ability to cope with blood loss, or loss of function, e.g. intra-cranial vs. intra-cerebral, cardiac tamponade, rentinal)

Rate

Volume blood loss

Question 14

what are 2x types of external haemorrhage

Answer 14

Skin, GIT

Question 15

Describe some other potential causes of haemorrhage

Answer 15

Parasitism, 
bleeding disorders (coagulopathies e.g. rat bait ingestion, haemophilia) 
Organ rupture 
Tumour 
Inflammation 
Ulceration

Question 16

what signs characterise disorders of primary haemostasis?

Answer 16

Inability to form a PLATELET plug. Will continue to bleed for a few minutes until formation of a FIBRIN plug

Question 17

What kind of haemorrhages manifest in primary haemostats disorders

Answer 17

Petechiae, purpura, ecchymoses (haematomas uncommon)

Question 18

clinically, what signs will and animal show if it has a primary haemostasis disorder

Answer 18

epistaxis, haematuria, haematemesis, melaena, haematochezia.

Bleeding immediately after venipuncture
Small volume bleeds
Usually from multiple sites
From MM, into skin & over serosal surfaces

however will only bleed for a few mins, before formation of a fibrin plug

Question 19

What are the 4x mechanisms repsonsible for defects in primary haemostasis?

Answer 19

1. PLATELET DEFICIENCY Thrombocytopaenia
2. PLATELET DYSFUNCTION Thrombocytopathy, thrombopathy, thrombopathia
3. vW disease
4. damage to small blood vessels

Question 20

What are the 4x mechanisms responsible for defects in secondary haemostasis?

Answer 20

1. Inherited deficiency of coagulation factors
2. Vit K deficiency
3. Severe acute/ chronic hepatic parenchymal disease
4. Excessive fibrinolysis, fibrinogenolysis

Question 21

How does a combined disorder of both primary and secondary haemostasis manifest?

Answer 21

DIC!

Question 22

clinically, what signs will an animal show if it has a secondary haemostasis disorder

Answer 22

Delayed bleeding after venipuncture
Large volume bleeds (muscles, joints, body cavities)
Petechiae, ecchymoses, haematomas common

Question 23

What 4 mechanisms are responsible for thrombocytopenia

Answer 23

1. Dec platelet production in marrow
2. Sequestrum platelets
3. Destruction platelets
4. Consumption platelets

Question 24

Which mechanisms causing thrombocytopaenia are most likely to cause clinical signs?

Answer 24

In cats –> Dec platelet production
E.g. due to viral infection (FeLV), myeloproliferative, lymphoproliferative disease

In dogs –> immune mediated platelet destruction where antibodies attack platelets.

Question 25

How do we describe/ classify an immune mediated thrombocytopenia?

Answer 25

If we don’t know the cause -> primary IM thrombo.

If we DO know the cause- > secondary (e.g. drug induced, lymphoma, auto immune disease)

Question 26

What is the most common mechanism of thrombocytopenia in catties and why? What’re underlying conditions in cats commonly??

Answer 26

Myelophthisis, haemopoetic bone marrow is replaced by neoplastic tissue :( Consequence of chronic myeloproliferative disease.
OR
Retroviral infection - FeLV

Question 27

What is the most common mechanism of thrombocytopenia in dogs?

Answer 27

Immune mediated disease

primary= antibodies against platelets 
Secondary= lymphoma, bacteria, virus, drugs, vaccines (treat cause)

Question 28

Describe how vWF is essential for clotting

Answer 28

expressed by sub-endothelial CT and endothelium –> complexes with factor VIII –> clot stabilisation+ prevents proteases

Question 29

What is the different between types 1-3 and acquired vWBD ?

Answer 29

Type 1- Low plasma conc. Common. Doberman Pinscher, German shepherd, Goldie, poodle.
Type 2- lack of some monomer. Severe
Type 3- little-no vWF, severe (Scottish terrier)
Acquired- high shear force reduces functionality

Question 30

When will dogs show clinical signs when experiencing vWD type 1?

Answer 30

When conc vWBF falls below 20%

Question 31

What are some mechanisms by which blood vessel damage can predispose to a primary haemostatic disorder?

Answer 31

• circulating toxins
• bacteramia/viraemia
• uraemia
• BV fragility
• Immune mediated vasculitis