DVT Flashcards
definition of DVT
Formation of a thrombus within the deep veins (most commonly of the calf or thigh).
RF for DVT
- increased age
- pregnancy
- synthetic oestrogen
- trauma
- surgery (especially pelvic/ortho)
- past DVT
- cancer
- obesity
- immobility
- thrombophilia disorders eg protein C deficiency
- OCP
- smoking
- polycythaemia
- long bone fractures
- dehydration
- anti-phospholipid syndrome
virchow’s triad for DVT
venous stasis, vessel wall injury, blood hypercoagulability
epidemiology of DVT
common Estimated 145 per 100,000.
Long-term complications of DVT (venous insufficiency, ulceration) affect 0.5% population.
occurs in 25-50% of surgical patients, and many non-surgical patients
65% of below-knee DVTs are asymptomatic; these rarely embolize to the lung
sx of DVT
calf warmth, tenderness, swelling or erythema
mild fever
pitting oedema
asymptomatic
signs/symptoms of PE
signs of DVT
swelling
calf tenderness
severe leg oedema and cyanosis (phlegmasia carulea dolens) rare
resp exam for signs of PE
Well’s clinical prediction score
Ix for DVT
Calculate a Wells score before ordering D-dimer (D-dimer sensitive but not specific, also raised in pregnancy, infection, malignancy, and post-op)
thrombophilia tests before commencing anticoagulant therapy if no predisposing factors, in recurrent DVT or if DVT is in an unusual site.
Look for underlying malignancy - Urine dip; FBC, LFT, Ca2+; CXR±CT abdomen/pelvis (and mammography in female) if >40yrs.
doppler US - gold standard, good sensitivity for femoral veins, less sensitive for calf
blood
- d-dimer
- FBC - platelet count prior to starting heparin
- UE
- clotting
ECG, CXR, ABG - if suggestion PE
well’s score
= 1 = DVT unlikely = perform D-dimer, if negative DVT excluded, if positive, proceed to USS (if -ve DVT excluded, if +ve treat as DVT)
>/=2 = DVT likely = do d-dimer and USS, if both -ve exclude DVT, if USS +ve treat DVT, if D-dimer +ve and USS -ve repeat USS in 1 week
DVT prophylaxis
All inpatients assessed for DVT/PE risk and offered prophylaxis if appropriate.
stop pill 4wks pre-op
mobilise early
LMWH eg enoxaparin 20mg/24h SC, increase to 40mg for high-risk patients, caution if low GFR
graduated compression stockings (‘thromboemobolic deterrent stockings’) and intermittent pneumatic compression devices reduce risk of DVT by ~70%in surgical patients.
Fondaparinux(a factor Xa inhibitor) reduce risk of DVT over LMWH in eg major orthopaedic surgery without increasing risk of bleeding.
DVT Mx
LMWH (eg enoxaparin 1.5mg/kg/24h SC) or fondaparinux while waiting for therapeutic INR from warfarin anticoagulation. LMWH is superior to unfractionated heparin(used in renal failure or if increased risk of bleeding; dose guided by APTT
cancer pts should receive 6months LMWH then review
in others start warfarin simultaneously with LMWH (warfarin is prothrombotic for the 1st 48hrs)
stop heparin when INR is 2-3, treat for 3 months in most.
direct oral anticoagulents eg dabigatan, apixaban, rivoraxaban, are newer alternatives licensed for the treatment of DVT with benefits relating to simpler dosing and monitoring and reduced bleeding risk.
Inferior vena caval filters may be used in active bleeding, or when anticoagulants fail, or higher risk of PE; to minimize risk of PE. Post-phlebitic change (pain, swelling, and skin changes) can be seen in 10–30%—graduated compression stockings may help.
not above knee - treatment anticoag for 3mo
beyond knee - anticoag for 6mo
recurrent DVT may need liong term warfarin
complications of DVT
PE
damage to vein valves and chronic venous insufficiency of lower limb - post-thrombotic syndrome
rare: venous infarction (phlegmasia cerulea dolens).
complications of DVT Mx
heparin induced thrombocytopenia
bleeding
Px of DVT
Depends on extent of DVT; below-knee DVTs lower risk of embolus; more proximal DVTs have higher risk of propagation and embolisation, which, if large, may be fatal.
65% of below-knee DVTs are asymptomatic; these rarely embolize to the lung.
