Deep vein thrombosis

A. Presentation

Cannot be diagnosed reliably on clinical grounds.

Often asymptomatic.

The leg may be warm and swollen, with calf tenderness and superficial venous distension.

 

 

B. Investigation

Blood test

• FBC
• Coagulation studies
• D-dimer
  -> Negative result excludes diagnosis in low risk cases.

 

Compression ultrasound

Bilateral compression ultrasound of the common femoral, popliteal and distal popliteal veins

If clinical suspicion is high, but scan result is negative, do venography.

 

Doppler ultrasound

May miss calf-vein thrombosis. Thus in the presence of high clinical suspicion, a negative result means the test should be repeated in 7 days to detect patients with proximal extension.

 

Impendance plethysmography

Less sensitive than ultrasound

 

Venography is the gold standard, but carries almost 5% risk of inducing DVT.

 

C. Treatment

Before anticoagulation therapy is started, blood should be collected for:

• Activated partial thromboplastin time (aPTT)
• International normalised ratio (INR)
• Platelet count

 

Give pain relieft if necessary

 

Low molecular weight heparin (must)

LMWH (e.g. enoxaparin, dalteparin) is at least as effective and as safe as an IV unfractionated heparin in the initial management of DVT. LMWH does not require laboratory monitoring and thus is the drug of choice.

LMWH should be given for a minimum of 5 days AND until the INR has been >2 for 24-48 hours.

 

Warfarin (must)

- Oral anticoagulation (warfarin) may be commenced on the same day as LMWH.

- INR should be monitored daily and dose adjusted according to INR until a therapeutic level is achieved.

- Warfarin should not be commenced alone, i.e. without LMWH, as this is associated with a high rate of subsequent DVT recurrence.

- Warfarin should be continued for at least 3 months after the first episode of DVT, and longer after the second episode of DVT. Indefinitely for idiopathic cases and recurrent venous thromboembolism.

 

Catheter-directed thrmobolysis (optional)

May reduce the risk of post-thrombotic syndrome but carries a risk of major bleeding of 10%.

 

D. Other notes

DVT occurs most commonly in the lower limbs

 

Complications

• Pulmonary embolism (occurs in 50% of patients with proximal DVT, in 5% of those with distal DVT)
• Post thrombotic syndrome (occurs in 60% of patients with DVT)

 

Post-thrombotic syndrome

Occurs most commonly after iliofemoral DVT.

Characterised by pain, swelling, venous hypertension changes (e.g. leg ulceration)

 

Clinical predicition rule to rank DVT risk

Ask about:

• Active cancer
• Paralysis, paresis, or plaster immobilisation of a leg
• Recent bedridden >3 days or major surgery within the past 4 weeks.

Look for:

• Localised tenderness over distribution of the deep vein
• Entire leg swollen
• Calf circumference 10cm below tibial tuberosity >3cm greater than other calf
• Pitting oedema (but not varicose) veins
• Collateral dilated (but not varicose) veins
• (MINUS 2 points) An alternative diagnosis as or more likely than DVT

Add up the points.

<0: low risk

1-2: moderate risk

>3: high risk

 

Risk stratification of DVT risk for hospitalised patients

High (40% to 80%)

Medical

• Stroke
• Age >70yo
• Congestive heart failure
• Shock
• History of DVT/PE
• Thrombophilia

Surgical

• Orthopaedic surgery of pelvis, hip, or lower limb
• Major surgery, age >60yyo
• Major surgery, age 40-60 yo, with history of cancer, DVT/PE, or other risk factors (e.g. hypercoagulability conditions)
• Thrombophilia

 

Moderate (10% to 40%)

Medical

• Immobilised patient with active disease

Surgical

• Major surgery, age 40-60 yo
• Minor surgery, age >60 or age 40-60 yo with history of DVT/PE or oestrogen therapy

 

Low (<10%)

Medical

• Minor medical illness

Surgical

• Major surgery, age <40
• Minor surgery, age <60

 

Prevention

Pharmacological and non-pharmacological methods of prophylaxis are effective and their use in combination is additive.

 

Pharmacological prophylaxis

Unfractionated heparin (UFH) is the appropriate pharmacological methods in most cases.

 

Low molecular weight heparin is superior to UFH in preventing DVT in patients undergoing orthopaedic surgery, but has greater risk of epidural haematoma in patients undergoing epidural anaethesia.

 

Non-pharmacological prophylaxis

Graduated compression stocking

Sequential pneumatic compression device

Pneumatic foot compression device

 

Other measures

Adequate hydration

Early mobilisation

Leg elevation

Education