Blood

Question 1

Primary haemostats involves

Answer 1

Platelet plug formation: sub-endothelial matrix, vWF, platelets

Question 2

Secondary haemostats involves

Answer 2

Fibrin formation from fibrinogen via thrombin

Cross links & stabilises the clot

Question 3

Testing if you suspect primary coagulopathy

Answer 3

1. platelet count
2. consider buccal mucosal bleeding time
3. measure von Willebrand’s factor - ELISA

Question 4

Testing if you suspect secondary coagulopathy

Answer 4

1. one stage prothrombin time + activated partial thromboplastin time
   (if would need to wait for external tests can opt for whole blood clotting time + activated clotting time)
2. Check serum biochemistry - liver function

Question 5

Extrinsic pathway is initiated by

Answer 5

Tissue factor exposed on damaged tissue or released from activated endothelial cells
- binds factor 7
= principle initiator of the coagulation cascade

Question 6

Intrinsic pathway

Answer 6

Amplifies coagulation cascade response

Start with factor 12 activation by surface contact (-ve charge) or thrombin.

Question 7

APTT

Answer 7

Activated partial thromboplastin time - tests intrinsic and common pathways
Prolonged if clotting factors <30% normal level

Question 8

OSPT

Answer 8

One stage prothrombin time - tests extrinsic common pathway.
Sensitive to fact VII deficiency.

Question 9

Test for factor VII deficiency

Answer 9

one stage prothrombin time

Question 10

Emergency clotting test

Answer 10

Whole blood clotting time - plain glass tube, see how long it takes to clot - intrinsic + common pathways.

Question 11

Disorders of primary haemostasis

Answer 11

1. thrombocytopenia
2. thrombocytopathia
3. vWF deficiency

Question 12

Clinical signs primary haemostats

Answer 12

petechiae (±pupura) & ecchymosis
± bleeding from mucosal surfaces - melena epistaxis, haematuria
- excessive bleeding after sx
- occasional CNS bleeding
only a small amount of blood leaks out before it is sealed by a fibrin clot.

Question 13

Pre-surgery in Dobermans

Answer 13

Do a buccal mucosal bleeding time test - if prolonged delay sx and test for vWF.

Question 14

Disorders of secondary haemostasis

Answer 14

1. inherited deficiencies of coagulation factors e.g. Haemophilia A = factor VIII deficiency.
2. acquired deficiencies of coagulation factors - liver dz, warfarin toxicity.

Question 15

Clinical signs of secondary haemostasis disorders

Answer 15

• Bleeding into body cavities, joints, bruising (rarely petechiae)
• Haematomas - excessive bleeding following sx, trauma, venepuncture.
• Mucosal or surface bleeds less common

more severe bleeding as platelet plug forms but is unstable - washed away.

Question 16

Mixed primary and secondary coagulation disorders

Answer 16

DIC

Angiostrongylus vasorum infection

Question 17

Indicators of thromboembolic disease

Answer 17

1. increased fibrin degeneration products
2. high D-dimer levels
3. high Antithrombin III levels - increased risk of thrombosis

Question 18

TEG

Answer 18

thromboelastography - used to detect hyper & hypocoagulable states
Citrated whole blood used <4hrs old
ECC & referral only

Question 19

Blood volume of a cat

Answer 19

60-70ml/kg

Question 20

Blood volume of a dog

Answer 20

88ml/kg

Question 21

Clinical signs of >20% blood loss

Answer 21

Increasing pulse rate, increased respiratory rate, decreasing blood pressure, pale mms, weakening pulses.
If conscious - confusion or abnormal behaviours

Question 22

Below PCV 21%

Answer 22

Oxygen carrying capacity severely compromised

Question 23

What are the 3 plasma proteins?

Answer 23

Albumin, globulin, fibrinogen

Question 24

High PCV/Hb is linked to

Answer 24

Dehydration
Stress
Polycythemia - e.g. myeloproliferative disease or over production of erythroprotein.

Question 25

Broadly a lack of platelets is due to

Answer 25

reduced production, consumption e.g. DIC haemorrhage

Question 26

Potential tx is sx required and dog has reduced vWF

Answer 26

Desmopressin - stimulates release from the vascular endothelium. Cyroprecipitate containing vWF

Question 27

Blood product options

Answer 27

1. whole blood 2. plasma 3. packed rbcs 4. cryoprecipitate

Question 28

Whole blood transfusion is used for

Answer 28

Blood losses >30% in eunaemic patients Clotting disorders Severe anaemia - care if normovolaemic

Question 29

Blood typing/cross matching

Answer 29

Not essential in 1st transfusion for dogs | Essential for cats

Question 30

Plasma transfusion is used for

Answer 30

Hypoproteinaemia | Clotting disorders - fresh or fresh frozen

Question 31

Packed red cell transfusion is useful for

Answer 31

Anaemic but normovolaemic patients - increased oxygen carrying capacity. Suspension diluted before administration.

Question 32

Cyroprecipitate

Answer 32

Formed from centrifuging thawed fresh frozen plasma - used in clotting factor deficiencies to avoid plasma volume overload

Question 33

Potential blood products for clotting factor disorders

Answer 33

Whole blood, plasma, cyroprecipitate

Question 34

Potential blood products for anaemia

Answer 34

Whole blood, packed red cells

Question 35

Autotransfusions

Answer 35

Can be planned for surgery if blood loss expected. | 10d prior provided the animal is not anaemic - take <10% circulating volume, store at 4degrees until sx.

Question 36

Potential problems with transfusions

Answer 36

``` Transfusion reactions - if severe IV haemolysis can - renal failure & DIC Volume overload Bacterial contamination Emboli - insufficiently mixed/ no filter Hypocalcaemia if large vols Disease/exfoliating tumour transmission. ```