Introduction and overview to haemostasis

Question 1

Define haemostasis

Answer 1

arrest of bleeding and maintenance of vascular patency

Question 2

what are the requirements of haemostasis

Answer 2

it is ready at any time and immediate to act
acts at local site of injury
protection against unwanted thrombosis

Question 3

what are components of a normal haemostatic system

Answer 3

primary haemostasis - platelet plug
secondary haemostasis - fibrin clot
fibrinolysis
anticoagulant defences

Question 4

what kind of disorder do you have if your haematostatic system is underactive

Answer 4

bleeding disorder

Question 5

what kind of disorder do you have if your haematostatic system is overactive

Answer 5

clotting disorder

Question 6

what are megakaryocytes

Answer 6

large multinucleate cells found in the bone marrow only

Question 7

how are platelets formed

Answer 7

budding off from megakaryocytes

Question 8

what are platelets

Answer 8

small anucleate rings with a lifespan of 7-10days

Question 9

how long should a patient stop antiplatelets prior to surgery

Answer 9

1 week

Question 10

what is primary haemostasis

Answer 10

formation of platelet plug

Question 11

is a platelet plug strong

Answer 11

no, it is weak

suitable for small injuries but not sufficient in greater damage

Question 12

explain the process of primary haemostasis

Answer 12

Endothelial damage exposes collagen
Platelets and VWF bind to collagen
VWF helps platelets adhere to collagen and other platelets
Secretion of other chemicals help platelet aggregation

Question 13

what are causes of failure of primary haemostasis

Answer 13

vascular: collagen deficiency
platelets: reduced number or function
VWF deficiency

Question 14

what are symptoms and signs of primary haemostatic failure

Answer 14

spontaneous bruising 
senile purpura 
purpura on legs 
mucosal bleeding: nose, conjunctiva, mouth, GI tract, menorrhagia 
intracranial haemorrhage
retinal haemorrhage - fundoscopy

Question 15

what investigation can be done for primary haemostatic failure

Answer 15

platelet count

Question 16

what is the term for high platelets

Answer 16

thrombocytosis

Question 17

what is the term for low platelets

Answer 17

thrombocytopaenia

Question 18

what is secondary haemostasis

Answer 18

formation of fibrin clot

Question 19

is a fibrin clot strong

Answer 19

yes, fibrin strengthens the platelet plug

Question 20

platelets are full of -ve phospholipids and Ca2+, true or false

Answer 20

true

Question 21

clotting factors are negatively/positively charged

Answer 21

negatively charged

Question 22

explain the process of secondary haemostasis

Answer 22

Tissue Factor activates factor 7
this complex activates factors 5+10
these then activate prothrombin to form thrombin
thrombin then converts fibrinogen to fibrin
fibrin is the final product
thrombin also acts in a positive feedback to activate factors 8+9
8+9 also activate factors 5+10
whole process is amplified

Question 23

list the main categories for failure of secondary haemostatic failure

Answer 23

single deficiency

multiple deficiencies

Question 24

features of single deficiency in secondary haemostatic failure

Answer 24

hereditary
rarer
eg haemophilia

Question 25

which clotting factor is deficient in haemophilia A

Answer 25

factor 8

Question 26

which clotting factor is deficient in haemophilia B

Answer 26

factor 9

Question 27

what is a cause of multiple deficiencies in secondary haemostatic failure

Answer 27

disseminated intravascular coagulation DIC

Question 28

list causes of DIC

Answer 28

``` sepsis cancer ABO incompatibility RTA liver disease ```

Question 29

what is the pathophysiology behind DIC

Answer 29

increase in clot formation leading to widespread ischaemia | paradoxically there is also increased bleeding due to depletion of clotting factors

Question 30

what is fibrinolysis and what is its purpose

Answer 30

break down of fibrin clots to maintain vascular patency occurs when fibrin clot has formed and bleeding has stopped

Question 31

what is the process of fibrinolysis

Answer 31

tPA activates plasminogen into plasmin | plasmin breaks fibrin into FDPs

Question 32

what are d dimers

Answer 32

fibrin degradation products

Question 33

generally, failure of secondary haemostasis has characteristic symptoms, true or false

Answer 33

false

Question 34

what are symptoms of single deficiency secondary haemostatic failure

Answer 34

bleeding into joints and muscles

Question 35

what tests can be done to investigate fibrin clot formation as coagulation screen

Answer 35

prothrombin time PTT | activated partial thromboplastin time APTT

Question 36

what does prothrombin time measure

Answer 36

length of time taken for clot formation via extrinsic pathway

Question 37

prothrombin time measure extrinsic/intrinsic pathway

Answer 37

extrinsic

Question 38

which clotting factors can be tested in prothrombin time

Answer 38

TF/3, 7, 5, 10, PT

Question 39

clotting factors 8+9 are tested in prothrombin time, true or false

Answer 39

FALSE

Question 40

what does activated partial thromboplastin time (APTT) measure

Answer 40

length of time taken for clot formation via intrinsic pathway

Question 41

APTT measure extrinsic/intrinsic pathway

Answer 41

intrinsic

Question 42

which clotting factors are tested in APTT

Answer 42

8, 9, 5, 10, PT

Question 43

if there is a deficiency in factor 7, PT/APTT would be prolonged

Answer 43

PT

Question 44

if there is a deficiency in factor 8, PT/APTT would be prolonged

Answer 44

APTT

Question 45

list some naturally occurring anticoagulants

Answer 45

serine protease inhibitors eg anti thrombin | Protein C + S

Question 46

how does anti thrombin work

Answer 46

inhibits thrombin and so switches off haemostasis

Question 47

how do Protein C+S work

Answer 47

bind to factors 5+8 to switch off coagulation

Question 48

what would occur as a result of antithrombin/Protein C/S deficiency

Answer 48

excess clotting because you cant stop anticoagulation

Question 49

define thrombophilia

Answer 49

increased tendency to forming clots eg DVT, PE, VTE