DVT/PE Flashcards
What is the pathophysiology of thrombus formation?
Virchow’s triad:
Abnormal blood flow- usually due to recent immobility, such s long-distance flight or being bed-bound in hospital. Most common underlying cause of DVT.
Abnormal blood components - can be caused by multiple factors - smoking, sepsis, malignancy, inherited blood disorders (e.g. factor V leiden)
Abnormal vessel wall - atheroma formation, inflammatory response, direct trauma (e.g in surgery)
What are the risk factors for DVT/PE?
Increasing age Previous VTE Smoking Pregnancy/post-partum Recent surgery Prolonged immobility - > 3 days HRT or COCP Current active malignancy Obesity Known thrombophilia disorder
What is deep vein thrombosis?
Formation of a blood clot in the deep veins of limbs most commonly affecting those of legs or pelvis
What are the clinical features of DVT?
Unilateral leg pain and swelling
Pyrexia, pitting oedema, tenderness, prominent superficial veins
Can be asymptomatic (65%)
What scale should be used to assess DVT in a patient
Wells' score: Active cancer -1 Calf swelling >3 cm -1 Swollen unilateral superficial veins - 1 Unilateral pitting oedema - 1 Previous documented DVT - 1 Swelling of entire leg - 1 Localised tenderness along the deep venous system - 1 Paralysis, paresis or immobilisation of lower extremity - 1 Recently bedridder/major surgery - 1 Alternative diagnosis likely subtract 2
Score 1 or less - DVT is unlikely - do D-dimer to exclude
Score greater than 1 - DVT is likely so do a USS to confirm
What test should be done to rule out DVT/PE if it is unlikely?
D-dimer
This is sensitive but not specific
D-dimer may be raised following recent surgery or trauma with ongoing infection inflammation, concurrent liver disease or pregnancy
How is DVT managed?
DOACs
Factor Xa inhibitor - apixaban, rivaroxaban, edoxaban
Thrombin inhibitor - dabigatran
Dabigatran and edoxaban require initial treatment with LMWH (>5 days) before commencement of the DOAC
Vitamin K antagonist - warfarin which requires therapeutic LMWH to cover until the INR levels are sufficiently therapeutic
LMWH alone is recommended in patients with cancer associated VTE
Continue anticoagulation for 3 months in provoked DVT
However in proximal DVT and a persistent risk factor or high risk of DVT recurrence - lifelong anticoagulation
What is a PE?
Blockage of pulmonary rather by a substance that has travelled there in the bloodstream - often DVT embolism
Fat cells from tibial fracture, neoplastic cells, AF clotting,
What are the clinical features of PE?
Sudden onset dyspnoea, pleuritic chest pain, cough or rarely haemoptysis
Tachycardia, tachypnoea, pyrexia, raised JVP, pleural rub, pleural effusion (rare)
DVT signs
How would you assess PE risk and how would you proceed?
PE wells score Signs/symptoms of DVT 3 PE is most likely diagnosis 3 HR > 100 1.5 Immobilisation 3 days 1.5 Previous PE/DVT 1.5 Haemoptysis 1 Malignancy 1
4 or less - PE unlikely, D-dimer to exclude
more than 4 - PE likely CTPA to confirm or VQ scan in poor renal function patients who will not tolerate dye
What investigations would you do for PE?
CTPA
D-dimer to exclude
ECG for chest pain
May show RBBB
What is the management for PE?
Unstable PE - haemodynamic compromise - consider thrombolysis
Stable PE:
Anticoagulation for 3 months
DOACs
Factor Xa inhibitor - apixaban, rivaroxaban, edoxaban
Thrombin inhibitor - dabigatran
Dabigatran and edoxaban require initial treatment with LMWH (>5 days) before commencement of the DOAC
Vitamin K antagonist - warfarin which requires therapeutic LMWH to cover until the INR levels are sufficiently therapeutic
LMWH alone is recommended in patients with cancer associated VTE
Consider IVC filter for recurrent PE secondary to DVT
What are the methods of thromboprophylaxis?
Mechanical:
Antiembolic compression stockings (below or above knee)
Intermittent pneumatic compression (intraoperatively)
Early ambulation after surgery
Foot impulse devices
Pre-operative mobilisation
Pharmacological:
Low molecular weight heparin (dalteparin), unless poor renal function (eGCR<30) then consider unfractionated heparin
Fodaparinux sodium
All surgical patients should be offered mechanical prophylaxis. Pharmacological prophylaxis if risk of major bleeding is low
Also maintain hydration and stop pro-thrombotic drugs such as COCP
When is mechanical prophylaxis for VTE contraindicated?
Peripheral arterial disease
Peripheral oedema
Local skin conditions - cellulitis/psoriasis
What are the mechanisms of action and uses of LMWH, unfractionated heparin, dabigatran
LMWH: binds antithrombin resulting in inhibition of factor Xa
Used in patients with normal renal function at moderate/high risk of VTE, SC injection OD
Unfractionated heparin: binds antithrombin III which affected thrombin and factor Xa
Effective anticoagulation IV - rapid onset but therapeutic effects decline quickly on stopping. Activity is measred using APTT, can be reversed using protamine sulphate. Used in patients with poor renal function
Dabigatran - direct thrombin inhibitor
Used prophylaxis in hip and knee surgery, does not require monitoring, has no known antidote - should not be used in patient at risk of bleeding/imminent surgery
