Haemostasis Flashcards
What time is checked to monitor heparin therapy? Which pathway does this assess?
aPTT, Intrinsic Pathway
What is checked to monitor Warfarin therapy? What pathway does this assess?
PT (INR), Extrinsic Pathway
Which factor starts the Intrinsic pathway in the Coagulation Cascade?
Twelve
Which factor starts the Extrinsic Pathway in the Clotting Cascade?
Seven
What factor starts the Common Pathway? And what is used to monitor this pathway?
Five, TT (Thrombin time)
What 3 components make up Virchows Triad?
Vessel Wall, Blood, Blood Flow
What is the therepeutic range for INR?
2-3 (ideally 2.5)
What is given for DVT prophylaxis in ‘at risk’ patients?
Daily SC LMWH, TED stockings
What antithrombotic molecules are expressed by the vessel wall?
Thrombomodulin, EPCR, Tissue Factor Pathway Inhibitor (TFPI), Heparans
How does injury/inflammation make the vessel wall prothrombotic?
Down regulates anticoag mols, upregulates adhesion mols, expresses TF, decrease prostacyclin production
What antiplatelet factors are expressed by the vessel wall?
Prostacyclin, NO
What 3 factors make up the risk factors of blood in Virchows Triad?
Viscosity (Hct, protein/paraprotein), Plt count, Coagulation system
What is the treatment for DVT/PE?
TEDS +LMWH (175u/kg) + warfarin: LMWH stoped when INR in therepeutic range, Warfarin continued for 3-6 months unless recurrent VTE (give lifelong)
How long should you give a cancer patient LMWH after a VTE?
3-6 months
Which cancer is especially related to VTE’s?
Pancreatic
What percentage of idiopathic VTE’s are due to cancer?
10%
How does Heparin work?
Potentiates antithrombin III, which inactivates thrombin and factors 9,10, 11
How are LMWHs administered and how/when is it monitored?
SC once daily, only requires monitoring in late pregnancy and renal failure via anti-Xa assay
How is Unfractionated heparin administered and how is it monitored?
Given IV, loading dose then infusion, monitor APTT
What is the Antidote for Heparin?
Protamine Sulphate
What are the side effects of Heparins?
Bleeding, HIT (heparin induced thrombocytopenia), osteoporosis with long term use
How does Warfarin work?
Inhibits the reductase enzyme responsible for regenerating the active form of Vit K, therefore inhibits the synthesis of factors 2,7,9, 10, and proteins C, S and Z
How is Warfarin monitored and how is its effects reveresed?
INR (derived from PT), reversed with IV Vit K/factor concentrates
What are the 2 types of Direct Acting Anticoagulants? Give one example of each.
Anti-Xa (Rivoraxaban, Apixaban, Edoxaban), Anti-Iia/Anti-Thrombin (Dabigatran)
When is the target INR 2.5?
1st episode DVT/PE, AF, cardiomyopathy, symptomatic inherited thrombophilia, mural thrombus, cardioversion
When is the target INR 3.5?
Recurrent DVT/PE, mechanical prosthetic valve (2.5-3.5), coronary artery graft thrombosis, antiphospholipid syndrome
Management plan (Warfarin patient): INR 5-8, no bleeding
Withold few doses, reduce maintenance. Restart when INR under 5
Management plan (Warfarin patient): INR 5-8, minor bleeding
Stop warfarin. Vit K slow IV. Restart when INR under 5
Management plan (Warfarin patient): INR >8, no bleed/minor bleed
Stop warfarin. Vit K (oral/IV, no bleeding/risk factors for bleeding or minor bleeding). Check INR daily
Management plan (Warfarin patient): Major bleeding (incl Intracranial haemorrhage)
Stop warfarin. Give prothrombin complex concentrate. If unavailable, give FFP. Give Vit K IV.
Why does pregnancy increase the risk of a VTE?
increases VIII + fibrinogen, decreases proteins, compression on blood flow
How does malignancy increase the risk of a VTE?
TFs on tumour, inflammation (makes vessel wall prothrombotic), compression on blood flow
What is the mortality and recurrence rate of a VTE?
5% mortality, 20% recurrence in 2 years
List 5 acquired factors that increase the risk of a VTE.
Age (>60), BMI >30, Hx DVT/PE, Immobilisation, Major surgery, Long distance travel, malignancy, Pregnancy, HRT, Antiphospholipid Syndrome, Polycythaemia, Thrombocythaemia
List 5 Inherited factors that increase the risk of a VTE.
Antithrombin deficiency, Protein C def, Protein S def, Factor V Leiden, Prothrombin G20210A, Lupus Anticoag., Coag excess
What is the order of factors in the Intrinsic Pathway of the Coagulation Cascade?
TwelvE, EleveN, NinE, EighT, TeN –> Five joins it to Common Pathway
What turns Fibrinogen into Fibrin?
Thrombin
What turns Plasminogen into Plasmin?
Tissue Plasminogen Activators (TPA)
What turns Prothrombin into Thrombin?
Factor V (with Calcium + Platelet Factor)
What is increased and decreased in DIC? (INR, APTT, Thrombin Time, Plt Ct, Bleeding Time)
Increased: INR, APTT, TT, Bleeding time; Decreased: PltCt
What is increased and decreased in Liver Disease? (INR, APTT, Thrombin Time, Plt Ct, Bleeding Time)
Increased: INR, APTT Decreased: Plt Ct
What is increased and decreased in Vit K Def? (INR, APTT, Thrombin Time, Plt Ct, Bleeding Time)
Increased: INR, APTT
