venous thromboembolism

Question 1

virchows triad

Answer 1

stasis
hypercoagulabilty
vascular injury

Question 2

risk factors for venous thromboembolism

Answer 2

age
obesity
varicose veinse
previous vte
thrombophilia
cancer
other thrombotic states
hormone therapy
pregnancy, puerperium
immobility
immobility during travel
hospitalisation
anaesthesia
central venous catheters

Question 3

types of venous thrombosis

Answer 3

deep vein thrombosis
pulmonary embolism
cerebral, mesenteric, axillary, splanchnic, splenic

Question 4

lower limb dvt clinical features

Answer 4

pain, swelling, increased temp of limb, dilation of superficial veins
usually unilateral
- may be bilateral if thrombosis sited in inferior vena cava
- differential diagnosis - calf haematoma, ruptured baker’s cyst, cellulitis
clinical probability - well’s score

Question 5

dvt investigations

Answer 5

use of d-dimer as negative predictor of VTE
gold standard - contrast venography
venous ultrasonography
- non compressibility of common femoral vein or popliteal vein are diagnostic of dvt
- sensitivity 95%, specificity 96% for diagnosis of symptomatic proximal dvt
- sensitivity and specificity only 60-70% for isolated calf vein thrombosis

Question 6

PE clinical features

Answer 6

depends on number, size and distribution of emboli
collapse, faintness, crushing central chest pain
pleuritic chest pain
difficulty breathing
haemoptysis
exertional dyspnoea

Question 7

diagnosis of PE

Answer 7

chest xray
ECG
ABG
d-dimer
ventilation perfusion (V/Q) scan
ct-pulmonary angiogram
echocardiogram

Question 8

rapid initial anticoagulation

Answer 8

parenteral anticoagulant - heparin, low molecular weight heparin, fondaparinux
OR
direct oral anticoagulant
aim - to reduce risk of thrombus extension and fatal PE

Question 9

extended therapy

Answer 9

orally active anticoagulant - vit K antagonist
OR
direct oral anticoagulant
aim - to prevent recurrent thrombosis and chronic complications such and post-phlebitic syndrome

Question 10

direct oral anticoagulants

Answer 10

dabigatran, rivaroxaban, edoxaban and apixaban in UK - treatment for acute DVT
enables rapid initial anticoagulation orally
continue maintenance dose for 6 months or longer for secondary prevention of VTE
apixaban and rivaroxaban dont need overlap with heparin

Question 11

investigation of a procoagulant tendency

Answer 11

full blood count
antithrombin
protein c
free protein s
antiphospholipid antibodies and lupus anticoagulant
thrombin time/reptilase time to investigate fibrinogen function
factor 5 leiden, prothrombin 20210A genetic tests
jak-2 mutation to investigate myeloproliferative conditions
PNH screen - if patient has cytopenia, for splanchnic bed thrombosis

Question 12

who to test for thrombophilia

Answer 12

venous thrombosis < 45 years
recurrent venous thrombosis
family history of unprovoked thrombosis
combined arterial and venous thrombosis
venous thrombosis at unusual site

Question 13

what does dabigatran act on

Answer 13

factor 2a

Question 14

what do rivaroxaban, apixaban, edoxaban and batrixaban act on

Answer 14

factor 10a

Question 15

heparins

Answer 15

unfractioned
low molecular weight

Question 16

unfractioned heparin

Answer 16

heterogenous group of molecules with a range in MW from 3000 to 30,000D
unpredictable anticoagulant response due to binding plasma proteins
monitoring required by activated partial thromboplastin time

Question 17

unfractioned heparin properties

Answer 17

binds to plasma proteins so requires monitoring
monitor using APTT
continuous iv infusion or twice daily sc administration
risk of osteoporosis, heparin induced thrombocytopenia
reverse by d/c infusion, protamine

Question 18

low molecular weight heparin properties

Answer 18

nearly 100% bioavailability mean reliable dose dependent anticoagulant effect
no monitoring required unless renal impairment or extremes of body weight
once daily dosing
reduced risk of osteoporosis and HIT
cannot be reversed

Question 19

coumarins - e.g. warfarin

Answer 19

inhibit vit K dependent carboxylation of factor 2, 7, 9 and 10 in liver
causes relative deficiency of those coagulation factors
many drug interactions
required monitoring at least monthly or more
most common side effect - bleeding

Question 20

reversal of warfarin

Answer 20

is patient bleeding?
vit K - oral or IV
can reverse by administering deficient clotting factors
tendency to use factor concentrate in place of fresh frozen plasma

Question 21

DOAC indications

Answer 21

treatment of DVT and PE
prevention of cardioembolic events in patients with AF

Question 22

benefits of DOACs over warfarin

Answer 22

more predictable anticoagulant profile
fewer drug and food interactions
wider therapeutic window compared to warfarin
oral administration
no need for monitoring
simple dosing

Question 23

idarucizumab

Answer 23

humaised fab fragment
high binding affinity to thrombin

Question 24

prevention of venous thrombosis

Answer 24

mechanical - foot pumps, graduated compression stocking
pharmacological - LMWH, UFH, fondaparinux, dabigatran, rivaroxaban, warfarin