Blood clotting

Question 1

what are the stages of blood clotting?

6

Answer 1

injury
vascular phase
platelet phase (primary haemostasis)
coagulation phase (secondary haemostsis)
clot formation and stabilisation
clot dissociation

Question 2

what occurs during the vascular phase?

3

Answer 2

vessel vasoconstricts
injury exposes collagen in vessel wall
release of factors from vessel lining - ADP (platelets), tissue factor, endothelins

Question 3

what happens during the platelet phase?

4

Answer 3

exposed collagen, ADP and endothelin attract platelets
platelets adhere
platelets aggregate and release ADP and thromboxane A2 which attracts more platelets
platelets plug the vessel injury

Question 4

what happens during the coagulation phase?

4

Answer 4

coagulation cascade - proteins that lead to clot formation
intrinsic - in blood stream
extrinsic - in vessel
fibrinolysis happens in parallel - clot breakdown

Question 4

what medications affect clotting?

3

Answer 4

anti-platelets
anticoagulants
injectable heparin

Question 5

what is aspirin used for? (75mg and 300mg)

Answer 5

75mg once a day
* secondary prevention for coronary heart disease and transient ischaemic attack
300mg
* given in acute MI/stroke

Question 6

what is aspirin’s mechanism of action?

Answer 6

inhibits COX enzyme to reduce production of thromboxane A2, reducing platelet aggregation

Question 7

what is warfarin used for? and what is its mechanism of action?

2

Answer 7

prosthetic heart valves
inhibits production of vitamin K which is essential for coagulation factors 2,7,9,10

Question 8

what is the way of monitoring warfarin?

Answer 8

INR - international normalised ratio
blood test

Question 9

what does warfarin interact with?

5

Answer 9

metronidazole
fluconazole
NSAIDs
alcohol
grapefruit

Question 10

what drugs are included in DOACs and what are they used for?

4,3

Answer 10

edoxaban, apixaban, rivaroxaban, dibigatran
used for atrial fibrillation, PE and DVT

Question 11

what are DOACs mechanism of action?

Answer 11

inhibits factor X of the coagulation cascade so clot cannot form

Question 12

what are the advantages and disadvantages of warfarin and DOACs?

onset, dosing, food effect, interactions, monitoring, offset

Answer 12

Question 13

what are examples of injectable anticoagulants?and what are they used for?

2,3

Answer 13

low Mr heparin - dalteparin, enoxaparin
given after birth or significant surgery or unable to take DOACs

Question 14

what is the mechanism of action of injectable anticoagulants?

Answer 14

inhibits formation of factor Xa and thrombin so fibrin clot cannot form

Question 15

what are the general principles when a patient is on anticoagulants?

8

Answer 15

consult with GP/senior dentist if unsure
delay dental treatment until anticoagulant finished if planned
plan treatment for early in week and day
atraumatic surgery, staged
consider packing and suturing
ensure bleeding has stopped
give post-operative instructions
advise pt to take paracetamol instead of NSAIDs

Question 16

how does liver disease affect clotting?

3

Answer 16

reduced number of platelets and impaired function
results in tendency to bleed
impaired production of coagulation factors 1,2,5,7,9,10,11,13

thrombopoeitin TPO stimulates platelet production in liver

Question 17

what is thrombocytopenia? what are the causes?

1,2

Answer 17

low platelets
reduced production
* B12/folic acid deficiency
* liver disease
* leukaemia
* chemotherapy
increased destruction
* immune driven

Question 18

what is Von Willebrand disease?

2

Answer 18

inherited disease leading to abnormal and prolonged bleeding
absence of or defective von Willebrand disease

Question 19

what are the three types of von Willebrand disease?

Answer 19

type 1: partial deficiency of VWD, most common, mild
type 2: reduced function of VWD
type 3: complete deficiency of VWD, most rare, severe

Question 20

how do you cover VWD during dental treatment?

3

Answer 20

tranexamic acid mouthwash - mild
DDAVP/desmopressin - more likely to bleed
von Willebrand factor concentrate - severe

Question 21

what is haemophilia? what are the different types? how do you manage?

Answer 21

x-linked recessive disease causing spontaneous bleeding into joints and significant bleeding after trauma
* haemophilia A - deficient factor 8 - DDAVP/desmopressin or factor 8 concentrate
* haemophilia B - deficient factor 9 - factor 9 concentrate

Question 22

what should you avoid with LA with a patient with inherited bleeding disorders? what should you do instead?

Answer 22

try to avoid inferior alveolar nerve blocks = risk of bleeding from muscle
* buccal infiltration
* intra-papillary injections
* intra-ligamentary injections

Question 23

what blood tests are related to clotting?

4

Answer 23

full blood count
liver function test
INR
coagulation screen

Question 24

what does INR measure? what is the lab standard? what is the INR for a healthy person? what should INR be for dental treatment?

5

Answer 24

compares how long it takes for a pts blood to clot compared to lab standard: 2-4
higher number = longer to clot
healthy person = 1
should be <4 for treatment

Question 25

what is thrombophilia? what can it be caused by?

2

Answer 25

over-clotting of blood
caused by: antiphospholipid syndrome, protein C/S deficiency

Question 26

what elements of the clotting cascade prevent over-clotting?

3

Answer 26

protein C
protein S
antithrombin

Question 27

what is pulmonary embolism (PE)?

Answer 27

blood clot in the lung

Question 28

what is deep vein thrombosis (DVT)?

Answer 28

bood clot in the limbs - often leg

Question 29

what are risk factors for thrombophilia?

9

Answer 29

previous PE/DVT
prolonged immobility
plaster casts
combined contraceptive pill
surgical operation
acutely unwell (sepsis)
cancer
dehydration
pregnancy

Question 30

how is thrombophilia managed?

Answer 30

anticoagulants but can cause a bleeding risk in dental practice