Chapter 7 Bleeding and Haemostasis

Question 1

Describe the three phases of primary haemostasis

Answer 1

1. Adherence
2. Activation
3. Aggregation

Question 2

What is the lifespan of a canine/feline platelet?

Answer 2

6-8 days

Question 3

Draw the cascade model of coagulation

Answer 3

Question 4

What are the three phases of coagulation in the cell based model of coagulation?

Answer 4

Initiation, amplification and propagation

Question 5

What are the two fundamental paradigm shifts in the cell based model of coagulation (vs coagulation cascade)?

Answer 5

1. Initiator = tissue factor
2. Coagulation localised to and contolled by cellular surfaces

Question 6

Draw the cell based model of coagulation

Answer 6

Question 7

What are the three natural anticoagulant pathways?

Answer 7

antithrombin

activated protein C

tissue factor pathway inhibitor

Question 8

The normal endothelium controla platelet reactivity by which three known inhibitors?

Answer 8

1. Prostacyclin (PGI₂)
2. Ectoadenosine diphosphatase (ecto-ADPase)
3. Nitroc oxide

Question 9

Which are the two main factors that anti-thrombin inhibits?

Answer 9

II (thrombin) and X

Question 10

Which two factors does activated protein C inactivate?

Answer 10

V and VIII

Question 11

Which two factors does tissue factor pathwaty inhibitor inactivate?

Answer 11

X and subsequently TF-fVII complex

Question 12

Which molecule degrades fibrin?

Answer 12

Plasmin (pro-enzyme = plasminogen)

Question 13

What are normal BMBP times in the dog and cat?

What part of haemostasis does it reflect?

Answer 13

Dog: <3 minutes

Cat: 34-105s

Reflects in vivo primary haemostasis

Question 14

at what deficiency level (i.e. what % remaining) does an isolated deficiency of a single factor prolong PT or APTT?

Answer 14

<25-30% of normal concentration

Question 15

What are d-dimers?

Answer 15

Degradation products of cross-linked finrin.

Indicate the activation of thrombin and plasmin and are specific for active coagulation and fibrinolysis.

Question 16

Name to two ‘tests’ that enable global assessment of the haemostatic system.

Answer 16

Thromboelastography (TEG) and rotational thromboelastometry (ROTEM)

Question 17

What does R represent?

What does K represent?

What is angle a dependent on?

What does MA represent?

Answer 17

R = enzymatic portion of coagulation (secondary haemostasis)

K = clotting time, represents clot kinetics (clotting factors, fibrinogen, platelets)

Angle a =dependent on fibronogen (+ platelets and factors)

MA = ultimate strenght of fibrin clot, dependent primarily on platelet aggregation (+ lesser extent on fibrinogen)

Question 18

The clot shear elastic modulus (G) is a measure of overall coagulant status. What is the formula for G?

Answer 18

5000 x MA

G = ________________

(100-MA)

Question 19

List 3 broad categories of “disorders of primary haemostasis” and give a specific example of each

Answer 19

1. Thrombocytopaenia e.g. IMTP
2. Thrombocytopathia e.g. NSAID induced, vW disease
3. Vascular disorders e.g. vasculitis, Ehler-Danlos

Question 20

Lost the two broad categories of “disorders of secondary haemostasis” + give a specific example of each

Answer 20

1. Aquired e.g. Vitamin K deficiency, hepatopathy, DIC,
2. Inherited factor deficiencies: I, II, VII (=hypoproconvertinaemia), VIII (Haemophilia A), IX (haemophilia B), X (=Stuart=Prower trait), XI (Plasma thromboplastin antecedent deficiency)
3. (Non-pathologic e.g. factor XII deficiency = Hageman factor deficiency)

Question 21

Which 7 factor deficiencies exist and cause clinical disease?

Answer 21

1, 2, 7, 8, 9, 10, 11

12 non-pathologic

Question 22

List 6 factors that influence acute traumatic coagulopathy

Answer 22

1. tissue injury
2. hypoperfusion
3. systemic inflammation
4. acidaemia
5. hypothermia
6. haemodilution

Question 23

What tests are included in basic coagulogram?

Answer 23

Platelet count, PT and APTT

Question 24

By what factor do PT or APTT need to be proloned to cause haemorrhagic risk?

Answer 24

x1.5

Question 25

3 questions for work up of bleeding disorder?

Answer 25

1. Coagulopathy vs bleeding due to local factors 2. If coagulopathy, primary or secondary (primary = ecchymoses and mucosal bleeding, secondary = haematomas) 3. Inherited or aquired

Question 26

List the constituents of fresh frozen plasma, frozen plasma, cryoprecipitate, cryosupernatant

Answer 26

Question 27

What is desmopressin and what does it do? What dose?

Answer 27

Synthetic vasopressin analogue --\> release of subendothelial vWF (and VIII and plasminogen) 1-4 ug/kg sc or intranasally. (30 min onset of action, 2 hour duration). Used in Type 1 vW disease patients

Question 28

At what platelet level can spontaneous bleeding occur?

Answer 28

\<50, 000/uL

Question 29

Classify the three types of vW disease and give an example of a predisposed breed for each

Answer 29

Type 1: All monomers present but in educed concentrations. Doberman, Poodle, Type 2: Disproportionate loss of high molecular weight multimers. German pointers Type 3: Almost complete absence (\<0.1%). Shetland sheepdogs, Chesapeake bay retrievers, dutch kooikers

Question 30

What are the viatmin k dependent coagulayion factors? N.B these are the same factors that are present in (stored) frozen plasma

Answer 30

2, 7, 9, 10

Question 31

What is the name of the enzyme that recycles vitamin k?

Answer 31

Vitamin K epoxide reductase

Question 32

What is Virchows triad?

Answer 32

1. Abnormality of vessel wall 2. Abnormal blood flow e.g. stasis 3. Abnormal blood constituents e.g. hypercoagulability)

Question 33

Which vessels do arterial thromboembolisms tend to affect? And venous ones?

Answer 33

Arteria affect aorta (/branches), cerebrovascular and coronary Venous affect pulmonary (or splenic, mesenteric, portal, cava)

Question 34

List 10 possible causes of hypercoagulability

Answer 34

1. IMHA 2. neoplasia 3. hyperadrenocorticism 4. corticosteroid therapy 5. sepsis 6. PLN 7. cardiac disease 8. atherosclerosis 9. diabetes ellitus 10. necrotizing pancreatitis

Question 35

Describe initial, secondary and definitive assessment of PTE

Answer 35

_Initial:_ Blood gases haem + biochem TXR (pulmonary infiltrates, may see Westermark sign = regional oligemia = area of increased radiolucency. _Secondary:_ D-dimers echo (R ventricular/regional hypokinesis w sparing of cardiac apex, RA and RV dilation, pulmonary hypertension, pulmonary artery dilation, paradoxical septal wall motion, thrombus) _Defiitive:_ Selective pulmonary angiography Pulmonary scintigraphy CT angiography

Question 36

List 2 types of anticoagulant and 2 types of anti-platelet drugs: In which scenario would you use anti-platelet and when anticoagulant?

Answer 36

_Anticoagulant:_ Warfarin Heparin (unfractionated or LMWH) _Anti-platelet:_ Clopidogrel Asprin Use anticoagulant in venous thrombus and anti-platelet in arterial thrombus

Question 37

Define DIC

Answer 37

Syndrome characterized by systemic activation of coagulation, leading to widespread microvascular thrombosis that compromises organ perfusion and can contribute to organ failure.

Question 38

What criteria are used to 'diagnose' DIC?

Answer 38

Presence of an underlying codition that could trigger DIC + 3 of the following: * thrombocytopaenia * Pt or APTT elevation * elevated fibrin split products or d-dimers * hyperfibrinogenaemia * reduced anti-thrombin activity or red blood cell fragmentation.

Question 39

What is the cornerstone of treatment of DIC

Answer 39

Address underlying condition.