haematology - venous thrombosis Flashcards
risk factors for venous thrombosis
Virchows triad
- vessel wall
- blood
- flow
Wells scores for DVT
0 = low risk 1-2 = moderate risk 3-7 = high risk
Wells scores for PE
0-1.5 = low risk 2-6 = moderate risk 6.5-12.5 = high risk
high Wells score
US of affected limb
CTPA
intermediate Wells score
D dimer
if D dimer high -> US/CTPA
if D dimer low -> rule out
low Wells score
consider other
risk factors for venous thrombosis
age obesity previous DVT/PE immobilisation major surgery long distance travel malignancy pregnancy COCP HRT
inherited causes of venous thrombosis
antithrombin deficiency protein C deficiency protein S deficiency factor V leiden lupus anticoagulant
DVT prophylaxis
daily subcut LMWH
TED stockings
some DOACs licensed in post-op ortho patients
DVT/PE treatment
LMWH
warfarin or DOAC
stop LMWH once INR is 2-3
why is LMWH continued while warfarin is started
warfarin also affects protein C/S and can lead to procoagulant state before anticoagulant effect
recurrent VTE
lifelong treatment
duration of treatment for VTE
3 months minimum
provoked VTE: stop after 3 months
otherwise: risk stratification
action of heparin
potentiates antithrombin III which inactivates thrombin and factor IX, X, XI
LMWH delivery
subcut once daily
does not require monitoring unless late pregnancy, renal failure (monitor anti-Xa levels)
heparin infusion cautions
monitor APTT
antidote for heparin infusion
protamine sulphate
side effects of heparin
bleeding
heparin induced thrombocytopenia
HIT
osteoporosis with long term use
action of warfarin
inhibits reductase enzyme
no regeneration of active vit K
inhibits synthesis of factors II, VII, IX, X, and proteins C, S, and Z
adjust dose to maintain INR
caution with warfarin in
pregnancy
risk of teratogenicity
warfarin reversal
IV vit K (6 hours)
prothrombin complex concentrate - octaplex/beriplex (30 mins)
target INR for 1st episode of DVT/PE
2-3
target INR for recurrent DVT/PE
2.5-3.5
protocol if INR 5-8 with no bleeding
withhold some doses
reduce maintenance
restart when <5
protocol if INR 5-8 with minor bleeding
stop warfarin
slow IV vit K
restart when <5
protocol if INR >8
stop warfarin
oral/IV vit K
check INR daily
protocol if major bleeding
stop warfarin
prothrombin complex concentrate/FFP
IV vit K
