Deep vein thrombosis resident survival guide

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Abdurahman Khalil, M.D. [2]

Definition

Deep vein thrombosis (DVT) is the formation of a blood clot ("thrombus") in a deep vein.

Pretest Probability of DVT

Wells scoring system is used for predicting probability of DVT:

It is calculated based on following scoring criteria:
❑ Paralysis, paresis or recent orthopedic casting of lower extremity (1 point)
❑ Recently bedridden (more than 3 days) or major surgery within past 4 weeks (1 point)
❑ Localized tenderness in deep vein system (1 point)
❑ Swelling of entire leg (1 point)
❑ Calf swelling 3 cm greater than other leg (measured 10 cm below the tibial tuberosity) (1 point)
❑ Pitting edema greater in the symptomatic leg (1 point)
❑ Collateral non varicose superficial veins (1 point)
❑ Active cancer or cancer treated within 6 months (1 point)
❑ Alternative diagnosis more likely than DVT (Baker's cyst, cellulitis, muscle damage, superficial venous thrombosis, post phlebitic syndrome, inguinal lymphadenopathy, external venous compression) (-2 points)

The results are interpreted as follows:

Points	Probability
3-8 Points	High probability of DVT
1-2 Points	Moderate probability
-2-0 Points	Low Probability

Causes

Life Threatening Causes

Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated. Although, deep vein thrombosis is by itself not life threatening, if not treated it may progress to a condition called as pulmonary embolism. Pulmonary embolism is severely life threatening and often a fatal condition.

Common Causes

Congenital:

• Enzyme deficiency (protein S deficiency, protein C deficiency, antithrombin deficiency)
• Mutations (factor V leiden, prothrombin gene)
• Anatomic (May-Thurner syndrome, Cockett syndrome)

Acquired:

• Medications (oral contraceptives, hormone replacement therapy, tamoxifen)
• Illness (cancer, acute myocardial infarction, congestive heart failure, sepsis, burns)
• Prolonged immobilization (transcontinental flights, operation under general anesthesia, pelvic/hip surgery, stroke/paraplegia)

Diagnostic approach

Pre test probability of DVT

Low

Moderate

Moderate or high sensitivity D Dimer

High sensitivity D Dimer

Negative No further testing

Positive

Proximal vein compression ultrasonography

Negative No further testing

Positive

Negative No further testing

Positive Treat

Proximal vein compression ultrasonography

Whole leg ultrasonography

Negative

Positive Treat

Postive Serial ultrasounds over next 2 weeks

Negative No further testing

Repeat Compression ultrasonography after 1 week

Treat if thrombus extends proximally

Negative No further testing

Positive Treat

Pre test probability of DVT

High/Unknown

Whole leg ultrasound

Proximal compression ultrasonography

Negative No further testing

Positive Treat

Positive Treat

Negative

D Dimer

Negative No further testing

Positive

Repeat proximal compression ultrasonography in 1 week

Negative No further testing

Positive Treat

Management

Suspected DVT

Pretest probability

High/Moderate

Low

Start anticoagulation unless contraindicated, while awaiting results

Wait to start anticoagulation, if results will be available within 24 hours

DVT confirmed

Anticoagulants contraindicated

Anticoagulants not contraindicated

Treat with inferior vena cava (IVC) filter

Stable DVT

Acute DVT

Initiate treatment with warfarin 10 mg, first 2 days or other VKA's Adjust dose based on INR

Home conditions stable? Good living conditions Strong support from friends/family Access to hospital, in case clinical condition deteriorates Hemodynamic status stable?

Treat at home

Hospitalize and treat

Choose one of the following parenteral anticoagulants: LMWH > Fondaparinaux > IV UFH > SC UFH LMWH: Enoxaparin 1 mg/kg every 12 hours Tinzaparin 175 IU/kg four times a day Dalteparin 100 IU/kg every 12 hours Fondaparinaux: 7.5 mg once daily IV UFH: Recommended doses Bolus 80 U/kg followed by 18 U/kg/hour or Bolus 5000 U followed by 1000 U/hour SC UFH: 333 U/kg Initate VKA, continue parenteral therapy till INR > 2.0 over 24 hours Total duration of therapy: First time DVT: Treat for 3 months Recurrent DVT: Treat for 6 months Recurrent DVT with high/moderate risk of bleeding: Treat for 3 months

Do's

• For moderate to high probability suspicion start initial therapy while waiting for diagnostic test results. When there is a low probability, the decision of treatment will depend on the diagnostic test results.
• Start vitamin K antagonist(Warfarin) no more than 1 or days after start UFH or LMWH.The initial dose for the first 2 days should be 10 mg daily then in accordance to the required INR measurements.
• INR therapeutic ranges are 2.0-3.0 and Target INR is 2.5 and that is applied for patients with hypercoagulable state (antiphospholipid syndrome).
• For IV UFH administration use weight adjusted dose for the initial bolus(80 unit/kg) and the following continuous infusion(18 unit/kg/hr), and for subcutaneous UFH (first dose 333 units/kg, then 250 units/kg).
• For patients with CKD/ESRD reduce LMWH than standered dose.
• Fondaparinux administered subcutaneously in fixed doses 7.5 mg and if the patient weight>100 kg the dose will be 10 mg.

Don'ts

Avoid with VKA therapy all of the following:

• NSAIDs including cox-2 inhibitors.
• Antiplatelet unless benefit outweighs harm (ACS, mechanical valves, coronary stents or bypass surgery).
• Vitamin K supplement(not recommended).