Haematology 6: Venous Thrombosis Flashcards
List 4 anticoagulant molecules expressed by the endothelium ?
TFPI
Thrombomodulin
EPCR
Heparans
When using unfractionated heparin, how could you measure the level to see if the treatment is in the therapeutic window ?
APTT
anti-Xa assay
Which DOAC inhibits factor IIa ?
Dabigatran
Which DOACs inhibit factor Xa ?
Rivaroxiban
Apixaban
Edoxaban
(They have an X in the name)
What reading is INR derived from ?
PT
Can Warfarin be given during pregnancy ?
No its teratogenic
Which factors are inhibited by Warfarin ?
10
9
7
2
Protein C and Protein S
Remember 1972
List 5 risk factors for thrombosis ?
Cancer Surgery Obesity Elderly Immobility
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
Male sex
Proximal Thrombosis
Idiopathic
virchows triad - 3 factors contributing to thrombosis
blood composition (viscocity)
vessel wall
blood flow
which of the following does the blood vessel wall not express: thrombomodulin endothelial protein C receptor tissue factor tissue factor pathway inhibitor heparans
tissue factor
how does stasis promote thrombosis
accumulation of activated factors
promotes platelet adhesion
promotes leukocyte adhesion and transmigration
hypoxia produces inflammatory effect on endothelium
list 4 causes of stasis
immobility (surgery, travel)
compression (tumour, pregnancy)
viscosity (polycthaemia, paraprotein)
congenital (vascular abnormalities)
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
antithrombin deficiency
describe the use and action of heparin
immediate unfractionated (IV) LMWH (SC) pentasaccharide (SC) increases anticoagulant activity
disadvantages of heparin therapy
administered by injection
risk of osteoporosis
variable renal dependence
describe the use of warfarin therapy
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)
how do we monitor heparin therapy
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
describe action of DOACs
anti Xa: - rivaroXaban, apiXaban, edoXaban anti IIa: - dabigatran properties: - oral - immediate action (peak 3-4hrs) - useful in long term short half life - no monitoring
how do we monitor warfarin therapy
essential measure INR difficult because lots of variables at play: - dietary vit K intake - variable absorption - interaction with other drugs - teratogenic
what can be used as thromboprophylaxis
LMWH - eg tinzaparin 4500 u. clexane 40mg OD
ted stockings
flotron (intermittent compression)
sometimes DOAC +/- aspirin
describe treatment for DVT/PE
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
how long would you anticoagulate after VTE after minor precipitants (COCP, flights, trauma)
3 months
longer if other thrombotic or haemorrhagic rf present
