Haematology 6: Venous Thrombosis

Question 1

List 4 anticoagulant molecules expressed by the endothelium ?

Answer 1

TFPI
Thrombomodulin
EPCR
Heparans

Question 2

When using unfractionated heparin, how could you measure the level to see if the treatment is in the therapeutic window ?

Answer 2

APTT

anti-Xa assay

Question 3

Which DOAC inhibits factor IIa ?

Answer 3

Dabigatran

Question 4

Which DOACs inhibit factor Xa ?

Answer 4

Rivaroxiban
Apixaban
Edoxaban

(They have an X in the name)

Question 5

What reading is INR derived from ?

Answer 5

PT

Question 6

Can Warfarin be given during pregnancy ?

Answer 6

No its teratogenic

Question 7

Which factors are inhibited by Warfarin ?

Answer 7

10
9
7
2

Protein C and Protein S

Remember 1972

Question 8

List 5 risk factors for thrombosis ?

Answer 8

Cancer
Surgery
Obesity
Elderly
Immobility

Question 9

Which of these factors are associated with a higher risk of recurrence of DVT ?

Male sex
Female Sex
Proximal thrombosis
Distal thrombosis 
Post surgery 
Idiopathic

Answer 9

Male sex
Proximal Thrombosis
Idiopathic

Question 10

virchows triad - 3 factors contributing to thrombosis

Answer 10

blood composition (viscocity)
vessel wall
blood flow

Question 11

which of the following does the blood vessel wall not express:
thrombomodulin 
endothelial protein C receptor 
tissue factor 
tissue factor pathway inhibitor 
heparans

Answer 11

tissue factor

Question 12

how does stasis promote thrombosis

Answer 12

accumulation of activated factors
promotes platelet adhesion
promotes leukocyte adhesion and transmigration
hypoxia produces inflammatory effect on endothelium

Question 13

list 4 causes of stasis

Answer 13

immobility (surgery, travel)
compression (tumour, pregnancy)
viscosity (polycthaemia, paraprotein)
congenital (vascular abnormalities)

Question 14

which of the following factors confers the highest risk of thrombosis:
factor V leiden
antithrombin deficiency 
FHx of thrombosis 
reduced factor VIII level 
3 hr plane flight

Answer 14

antithrombin deficiency

Question 15

describe the use and action of heparin

Answer 15

immediate 
unfractionated (IV)
LMWH (SC) 
pentasaccharide (SC)
increases anticoagulant activity

Question 16

disadvantages of heparin therapy

Answer 16

administered by injection
risk of osteoporosis
variable renal dependence

Question 17

describe the use of warfarin therapy

Answer 17

vitamin K antagonist
reduces procoagulant activity - 2,7,9,10, protein C and S
delayed effect - factors have a half-life of 2-3 days
oral
reversible - by giving vitamin K (12 hrs) or factors 2,7,9,10 ( immediate)

Question 18

how do we monitor heparin therapy

Answer 18

LMWH - does not need monitoring
anti X a assays can be used

Unfractionated heparin - variable kinetics, variable dose response, always monitor therapeutic levels with APTT or anti-Xa

Question 19

describe action of DOACs

Answer 19

anti Xa:
- rivaroXaban, apiXaban, edoXaban 
anti IIa:
- dabigatran 
properties:
- oral 
- immediate action (peak 3-4hrs)
- useful in long term 
short half life 
- no monitoring

Question 20

how do we monitor warfarin therapy

Answer 20

essential 
measure INR 
difficult because lots of variables at play:
- dietary vit K intake 
- variable absorption
- interaction with other drugs 
- teratogenic

Question 21

what can be used as thromboprophylaxis

Answer 21

LMWH - eg tinzaparin 4500 u. clexane 40mg OD
ted stockings
flotron (intermittent compression)
sometimes DOAC +/- aspirin

Question 22

describe treatment for DVT/PE

Answer 22

start LMWH eg tinzaparin 175u/kg + warfarin
stop LMWH when INR>2 for 2 days

thrombolysis only used for life-threatening PE or limb-treatening DVT - increased risk of IC haemorrhage

Question 23

how long would you anticoagulate after VTE after minor precipitants (COCP, flights, trauma)

Answer 23

3 months

longer if other thrombotic or haemorrhagic rf present