HAEM - Platelets, Clotting and Coagulation/Anticoagulation

Question 1

What leads to platelet adhesion after endothelium is damaged?

Answer 1

Exposure of collage and vWF

Question 2

What does platelet adhesion lead to

Answer 2

Degranulation of platelets –> release ADP

Synthesise PG TXA2 –> VC + aggregation

Question 3

What does ADP do at site of endothelial damage

Answer 3

Stimulates platelet aggregation

Question 4

What activates the clotting cascade?

Answer 4

Receptors on platelet surface

Question 5

Mode of action aspirin

Answer 5

Irreversibly inhibits COX1

Preventing conversioon of AA –> endoperoxidases such as PGI2 and TXA2

Question 6

What can’t anucleate platelets form, PGI2 or TXAs

Answer 6

TXAs

Question 7

Causes of thrombocytopenia - reduced production (3)

Answer 7

Aplastic anaemia
Marrow infiltration
Marrow suppression

Question 8

Causes of thrombocytopenia - excess destruction (5)

Answer 8

ITP
Autoimmune - SLE, CLL, virus
TTP
HUS 
Sequestriation - hypersplenism

Question 9

PS thrombocytopenia (4)

Answer 9

Mucocutaneous bleeding
Bruising/purpura skin
Epistaxis/menorrhagia
Major haemorrhage (rare)

Question 10

Cause ITP - children

Answer 10

Virus/imms

Question 11

Cause ITP - adults

Answer 11

Autoimmune

Question 12

Ix ITP (3)

Answer 12

FBC - thrombocytopenia ONLY
BM - norm/incr megacaryocyte
Platelet ab +ve 70%

Question 13

Mx ITP - kids

Answer 13

No Tx necess

Question 14

Mx ITP - adults

Answer 14

1st line = CCS
IVIG
Splenectomy = 2nd line

Question 15

What does PT test (prothrombin time)

Answer 15

Extrinsic pathway

VII X, V, II + I

Question 16

When is PT prolonged (2)

Answer 16

Liver disease

If pt is on Warfarin

Question 17

What is INR

Answer 17

Ratio of pt’s PT to norm control

Question 18

Norm INR range

Answer 18

0.9-1.1

Question 19

Which drug dosing is IR used for

Answer 19

Warfarin

Question 20

What does APTT test

Answer 20

Intrinsic pathways

Question 21

Which factors are tested APTT

Answer 21

XII
XI
IX 
VIII = extrinsic 
X
V
II
I = common

Question 22

Which drug monitoring is APTT used for

Answer 22

Unfractioned heparin

Question 23

Which conditions are APTT raised in?

Answer 23

Haemophilia
vWD
Liver disease
DICs

Question 24

What does thrombin time

Answer 24

Adition of thrombin to pt plasma

Question 25

What pathway is tested in Thrombin time

Answer 25

``` Common pathway X V II I ```

Question 26

What prolongs thrombin time

Answer 26

Fibrinogen deficiency or abnorm fct or inhibits e.g. heparin

Question 27

What is INR

Answer 27

Ratio of patients PT to normal control

Question 28

What is APTT

Answer 28

Activated partial thromboplastin time | Addition of surface activator to plasma

Question 29

Which clotting factors are produced by the liver? (6)

Answer 29

``` I - fibroinogen II - prothrombin IV V VI VII ```

Question 30

What happens if any clotting factors produced by the liver decrease

Answer 30

INR increases

Question 31

What is required for Vit K absorption and why

Answer 31

Bile salts | As is fat soluble

Question 32

Vit K dependent factors (6)

Answer 32

``` II VII IX X Protein C Protein S ```

Question 33

Where is Vit K absorbed

Answer 33

Upper ileum

Question 34

Where is Vit K stored

Answer 34

Liver

Question 35

What is protamine

Answer 35

antidote to heparin

Question 36

What are the 4 mechanisms haemostasis occurs by

Answer 36

Behavioural (compression + elevation) Vascular spasm Platelet plug (rapid response) Fibrin clot

Question 37

What are the 4 control mechanisms in the clotting pathway?

Answer 37

Physical separation Protein C inhibitory pathway Antithrombin 3 Fibrinolysis

Question 38

What is protein C generated by

Answer 38

Vit K

Question 39

What is protein C activated by?

Answer 39

Thrombin

Question 40

What does protein C do once activated

Answer 40

Acts w/ co-factor S to induce fibrinolysis | Destroys 5 + 8 meaning no more thrombin made + inhibits stabilization of fibrin clot

Question 41

Which control mechanism does heparin enhance?

Answer 41

Antithrombin 3

Question 42

How does fibrinolysis work

Answer 42

Plasminogen --> plasmin (by tPA) | Plasmin breaks down fibrinogen + fibrin --> d-dimer

Question 43

How is t-PA release stimulated

Answer 43

Thrombin + APC (activated protein C)

Question 44

What happens to the deficiency of fibrinolysis in severe trauma

Answer 44

Efficiency is enhanced | --> hyperfibrinolysis

Question 45

What viscosity platelets are ideal

Answer 45

sticky

Question 46

Signs of VIt K deficiency

Answer 46

Increased PT | Haemorrhage

Question 47

Causes of Vit K deficiencies (3)

Answer 47

Malabsorptive conditions Cholestatic jaundice ( no bile salts) ABx - gut flora disturbance