Venous Thromboembolism

Venous thrombosis is the term used for a blood clot that forms within a vein. Venous thrombosis usually occurs below the knee in the deep calf veins and is most often associated with prolonged immobilization. Formation of venous thrombosis in the deep calf veins is referred to as a deep venous thrombosis or DVT.

Calf vein thrombosis can then propagate, in some cases into the lower thigh. If the clot breaks off and travels to the lungs, causing partial or full occlusion of pulmonary veins, it is called a pulmonary embolism (PE). ¹ Together, DVT and PE are referred to as venous thromboembolism (VTE).

The reported incidence of DVT among patients with TBI ranges from 11% to 54%. ^2-5 In the absence of prophylactic clot prevention, the estimated risk of developing DVT or PE is 20%. ⁶

There are three primary risk factors for VTE, referred to as Virchow’s triad. Formation of VTE thrombi requires one or more of the factors in Virchow’s triad.

• Length of stay in the ICU
• Number of days on a ventilator (>3days)
• Paralysis
• Immobility
• Orthopedic surgery
• Sepsis
• Prior history of DVT
• Advanced age
• Congestive heart failure
• Obesity
• Myocardial infarction
• Malignancy
• Pregnancy
• Oral contraceptive use
• Smoking

Deep Venous Thrombosis

• Calf swelling but can involve whole leg swelling
• Localized pain over deep veins
• Redness, discoloration of skin in affected leg
• Prominent superficial veins

Many DVT remain isolated to calf veins and are asymptomatic. Larger and more proximal DVTs are more likely to be symptomatic.

Pulmonary Embolus (PE)

• Sudden shortness of breath
• Increased heart rate
• Chest pain
• Pain with breathing (pleuritic pain)
• Dizziness

PE can be small or large and again smaller pulmonary emboli may be asymptomatic while larger pulmonary emboli are more likely to be symptomatic.

• Clinical features listed above (note these clinical features overlap with a number of other medical conditions)
• Recent immobility
• Recent surgery
• Lower extremity trauma
• Presence of active cancer
• Underlying chronic medical illness
• Use of oral contraceptives
• Family history of hypercoagulable state
• History of spontaneous abortion (related to antiphospholipid antibody syndrome
• Well’s criteria for PE or DVT (see screening)
• PERC rule to rule out PE (see screening)

None of these criteria have been specifically verified in ABI patients.

DVT

• Examine for lower limb swelling (leg circumference 10 cm below the tibial tuberosity (> 3 cm difference between legs}
• Focal tenderness over the path of deep veins (posterior calf, popliteal fossa and medial anterior thighs)
• Color changes
• Lower limb neurological exam (looking for paralysis)
• Peripheral vascular exam

PE

• Full cardiovascular exam
  
• Full respiratory exam

OSCE Examination Guides

• Lower limb neurological examination
• Peripheral vascular examination
• Respiratory examination
• Cardiovascular examination

None of these screening tools have been specifically verified in ABI patients.

Well's Criteria for DVT

• Active cancer
• Bedridden recently >3 days or major surgery within 12 weeks
• Calf swelling >3 cm compared to the other leg
• Collateral (nonvaricose) superficial veins present
• Entire leg swollen
• Localized tenderness along the deep venous system
• Pitting edema, confined to symptomatic leg
• Paralysis, paresis, or resent plaster immobilization of the lower extremity
• Previously documented DVT
• Alternative diagnosis to DVT as likely or more likely

Well’s Score > 2 means DVT is likely

Well’s Score < 2 means DVT is unlikely

Well's Criteria for PE

• Clinical signs and symptoms of DVT

• PE is #1 diagnosis OR equally likely
• Heart rate >100
• Immobilization at least 3 days OR surgery in the previous 4 weeks
• Previous, objectively diagnosed PE or DVT
• Hemoptysis
• Malignancy w/treatment within 6 months or palliative

Well’s Score > 4 means PE is likely

Well’s Score < 4 means PE is unlikely

PERC Rule (use to rule out PE)

• Age ≥50
• HR ≥100
• O₂ sat on room air <95%
• Unilateral leg swelling
• Hemoptysis
• Recent surgery or trauma (surgery or trauma ≤4 weeks ago requiring treatment with general anesthesia)
• Prior PE or DVT
• Hormone use (oral contraceptives, hormone replacement or estrogenic hormones use in males or female patients)

If any criteria are positive, the PERC rule cannot be used to rule out PE in this patient.

Deep Venous Thrombosis

• D-Dimer (breakdown product of cross-linked fibrin) – sensitive but non-specific for acute clot. If normal and Well’s Score is <2 than DVT is excluded; if elevated than move to ultrasound.
• Venous duplex ultrasound ¹⁰ – easy and inexpensive – high sensitivity and specificity in acute symptomatic DVT – able to rule out DVT
• Contrast venography – until recently considered gold standard for DVT but invasive and not recommended
• Magnetic resonance venography ¹¹ – less invasive than contrast venography but expensive and time consuming

Pulmonary Embolus

• Computed tomography pulmonary angiogram ¹²
• Pulmonary Ventilation (V) and Perfusion (Q) Scan ¹⁴

DVT

• D-dimer (see above)
• Baseline testing:
  • INR
  • BUN/Cr
  • Liver function tests
  • CBC

PE

• D-dimer (see above)
• CK, Troponin (rule out cardiac ischemia)
• Electrolytes
• CBC (rule out infection)
• Arterial blood gases (low blood oxygen levels – CO2 levels may also be low)

DVT

• Edema (often associated with paralysis of the lower extremity)
• Heterotopic ossification
• Fracture
• Varicose veins
• Superficial thrombophlebitis
• Ruptured Baker cyst
• Cellulitis
• Lymphedema
• Arterial insufficiency
• Hematoma

PE

• Pneumothorax
• Myocardial infarction
  
• Unstable angina
• Pericarditis
• Congestive heart failure
• Pneumonia
• Bronchitis
• COPD
• Asthma
• Pleural effusion
• Rib fracture
• Muscular strain
• Panic disorder

Prevention

Compression devices such as thromboembolism deterrent stockings, and intermittent pneumatic compression devices including arteriovenous foot pumps and sequential compression devices (SCDs) more for treatment of swelling.

• They are not effective for prevention.
• Overall, there is limited evidence in the ABI literature to support that compression devices are an effective prophylactic, particularly compared to low-molecular-weight heparin. ^16-19
• Multiple studies have found no significant differences between those who were treated with compression devices compared to those treated with pharmacological prophylaxis. ^16,17
• When pharmacological venous thromboprophylaxis is contraindicated or delayed after traumatic brain injury, physical methods (i.e., intermittent pneumatic compression stockings) should be utilized. ¹⁵

Prevention

Treatment

DVT

Recommendations of the American College of Chest Physicians:

• Proximal DVT of leg (above knee) – anticoagulation for a minimum of 3 months
• Isolated DVT of leg (below knee) – high risk of extension or severe pain – treat with anticoagulation
• Isolated DVT of leg – Acute isolated DVT without severe pain or high risk of extension – serial ultrasounds every 2 weeks

Anticoagulation with direct oral anticoagulants (dabigatran, rivaroxaban, apixaban) recommended over Warfarin which is in turn recommended over LMWH (enoxaparin).

Patients at high risk of bleeding (i.e., recent surgery) treat with intravenous VFH initially as it has a short half-life and can be reversed with protamine.

VTE and active cancer, obesity, pregnancy and hepatic disorders recommend LMWH

VTE with renal impairment treat with intravenous UFH followed by Warfarin.

Pulmonary Embolism

• Treatment with anticoagulation

Vena Cava Filters should be restricted to acute proximal DVT or pulmonary embolism where anticoagulation is not possible due to uncontrollable bleeding or high risk for life threatening bleeding or urgent surgery requiring anticoagulation be discontinued (Duffett et al. BMJ 2020; 370:m2177).

Once anticoagulation can be resumed IVC filter should be removed to limit complications.

DVT

PE