Thrombosis Flashcards
Thrombotic risk factors
Post-operative, especially orthopaedic Hospitalisation Pregnancy OCP Long-haul flights Cancer Obesity i.v. drug abuse
DVT presentation
Can be no symptoms at all – clinically silent
Unilateral calf swelling/ heat/ pain/ redness/ hardness
Differential diagnosis: cellulitis, Baker’s cyst, muscular pain
Are there any risk factors?
Potentially fatal if missed
~1000 cases per year in BSUH
Doppler Ultrasound
Ultrasound transducer produces a real-time two dimensional image of soft tissue structure
Colour duplex shows velocity and direction of blood flow
Veins non-compressible by U/S probe
Investigation of choice
D-dimer test
Likelihood of having a DVT can be assessed using the Wells risk score and doing a D-dimer test
D-dimers indicate activation of the clotting cascade
Low Wells score and negative D-dimer test have high negative predictive value (>99% NPV)
Initial treatment
Therapeutic anti-coagulation using sub-cut LMW heparin (such as tinzaparin or enoxaparin)
Dosing is according to patient’s weight
No monitoring is required
If the patient has renal impairment (creatinine clearance less than 30ml/min) then anti-coagulate with i.v. unfractionated heparin instead (maintain APTT 1.5-2.0)
Subsequent treatment
Load patient with oral warfarin for 3-5 days
Stop LMW heparin once INR > 2.0 for 2 days
1st DVT (femoral or iliac) - 6 months’ warfarin
2nd DVT/PE: lifelong warfarin
Maintain INR between 2.0-3.0 (target 2.5)
PE
Micro-emboli: asymptomatic
Classic symptoms:
- pleuritic pain - dyspnoea - haemoptysis
Massive: syncope, death
O/E, tachycardic, tachypnoeic, hypotensive
Investigations – V/Q scan
-> V/Q Scan (radio-isotope)
- > Underperfusion ~ V/Q mismatch
- > Limitation: underlying lung disease
- > ‘indeterminate’ scans – hence rarely done
Investigations - ECG
ECG
- > Sinus tachycardia
- > Atrial fibrillation
- > Right heart strain
-> Classic: SI, QIII, TIII (rare)
Investigations - CXR
CXR
- > Usually normal
- > Linear atelectasis
- > Small effusions
PE outcomes
5% mortality with treatment
4% develop pulmonary hypertension
Cause of death in 10-30% of in-patient post mortems
Up to 60% have micro-emboli at post mortem
A leading cause of ‘preventable’ death in the western world (25,000 deaths/yr in England)
Massive PE treatment
Signs of shock (hypotension, acute SOB)
Mx: thrombolysis and iv heparin
2-6% risk of serious bleeding
Standard treatment
LMW heparin injections – e.g. Tinzaparin
Warfarin (target INR 2.5) for 6 months
Consider underlying causes
LMW heparin is better if underlying cancer
IVC filters
Consider a DOAC (NOAC) as an alternative Dabigatran po (direct thrombin inhibitor) Rivaroxaban po (direct Xa inhibitor)
Thrombophilia screen
Sometimes done in younger patients with VTE
Inherited Factor V Leiden Prothrombin gene variant Anti-thrombin deficiency Protein C deficiency Protein S deficiency
Acquired:
Anti-phospholipid syndrome
