Week 21b - Bleeding and Clotting Flashcards
what are the components of the haemostasis system
vasoconstriction
platelet plug formation
blood clotting - lead to formation of fibrin
what systems prevent blood clotting
healthy endothelium
anti-thombins - prevent thrombin formation
proteins c and s inactivate clotting factors
fibrinolysis - plasmin breaks down fibrin - breakdown product of this is d-dimer - used in diagnosis
platelet plug formation
platelets adhere to site of vascular injury
platelet aggregation and activation
activation of coagulation cascade
formation of fibrin
haemostatic plug formed
what is tissue factor
a mix of lipoproteins and phospholipids released from damaged tissue
what happens in stage 2 of blood clotting
formation of prothrombin activator
what happens in stage 3 of blood clotting
formation of fibrin from fibrinogen
in what stage of blood clotting does tissue factor act
stage 1
dvt investigation - wells score 0/1
d-dimer
- if negative: consider alternatives, give safety netting advice
- if positive: doppler ultrasound leg
dvt investigation - wells score 2 or more
doppler ultrasound leg
- if negative: review in 5-7 days, may still be a dvt
- if positive: treat for dvt
dvt treatment
most patients treated with f10a inhibitors e.g. apixaban
low molecular weight heparin e.g. dalteparin followed by f10a inhibitors of warfarin
f10a inhibitors often called direct oral anticoagulants (DOACs)
virchow’s triad
thrombosis in the middle
3 corners - stasis, vessel wall injury, hypercoagulability
pulmonary embolus presentation - physical
breathlessness - most common
pleuritic chest pain
cough
calf/leg swelling
haemoptysis - less common
syncope - less common
pulmonary embolus presentation - clinical
tachycardia including atrial fibrillation
tachypnoea
crackles or reduced breath sounds - ~20%
elevated jugular venous pressure
pulmonary embolus treatment
oral f10a inhibitor - e.g. apixaban, rivaroxaban
low molecular weight heparin - e.g. dalteparin followed by either thrombin inhibitor e.g. dabigatran or vit K antagonist e.g. warfarin
treatment normally for 3 months after provoked PE or DVT
why is venothromboembolism risk increased in hospital patients
immobility
age
underlying conditions like heart failure
cancer
surgery - activated clotting system
inflammation - release of tissue factor