GenSurg.nz

Deep vein thrombosis

Section: Vascular Sub-section: Curriculum, page 102

Thrombotic Risk

  • In the Absence of Anticoagulant Therapy
    • AF alone: 2% / year risk of stroke
    • AF + ↑age /HT/ CHF/DM/ CVA or TIA 4% / year
    • Recent / recurrent DVT: 40% chance of recurrence
    • Prosthetic Heart Valve: 4% / year risk of CVA / thromboembolism
    • Bileaflet (St Jude) valve: 10% Aortic; 20% Mitral
    • Multiple St Jude Valves: 90% / year risk of thromboembolism
    • Single leaflet tilting valve (Bjork-Shiley) 23% Aortic
    • Mitral > Aortic
    • Cage Ball (Star Edwards) > Others

Virchow’s Triad

  • DVT in gen surg patients without treatment/ prophylaxis:  - 0.5 to 1.6 percent
    • Higher among those undergoing sսrgеry for mаligոаnсy (up to 3.7 percent)

Endothelial Injury

  • Trauma: Direct injury to blood vessels (fractures, contusions).
  • Surgery: Particularly orthopedic (hip, knee replacements) or major abdominal/pelvic surgeries.
  • Central Venous Catheters: Placement of lines or ports.
  • Atherosclerosis: Chronic vascular injury.
  • Inflammation: Vasculitis or systemic inflammatory conditions.
  • Radiation Therapy: Direct damage to vascular endothelium.

Hypercoagulability

  • Inherited thrombophilia
    • Factor V Leiden mutation.
    • Prothrombin G20210A mutation.
    • Deficiency of antithrombin, protein C, or protein S.
    • Polycythaemia
    • Thrombocytopenia
  • Acquired
    • Cancer (especially pancreatic, brain, or lung cancer).
    • Pregnancy and postpartum period.
    • Hormonal therapy (oral contraceptives, hormone replacement therapy).
    • Antiphospholipid syndrome.
    • Sepsis or systemic inflammatory response syndrome (SIRS).
    • Nephrotic syndrome (loss of anticoagulant proteins).
    • Obesity.
    • Smoking.

Stasis of Blood Flow

  • Immobility:
    • Prolonged bed rest (e.g., hospitalization).
    • Long-distance travel (flights >4 hours, car trips)
    • Surgery
      • Length of operation > 2 hours
      • Type of operation
        • Hip or knee surgery
        • Abdominal and pelvic surgery
        • Laparoscopic
  • Paralysis: Stroke or spinal cord injury.
  • Venous Obstruction:
    • Pregnancy (compression by the gravid uterus).
    • Tumors or mass effect.
    • Congestive heart failure.
    • Varicose veins or chronic venous insufficiency.
    • May-Thurner syndrome

Risk Groups & incidence

Peri-operative patients can be stratified using the Caprini model which is a cumulative score reflecting the number of risk factors present. Risk factors include:

  • Demographics
  • Concurrent illness
  • Recent surgery
  • Family or personal history
  • Nature of surgery

Patients are stratified as low, intermediate, or high, or very high risk and thromboprophylactic treatment reflects this.

Low risk

  • < 30 minutes and age < 40 without additional risk factors
  • Outpatient surgery, laparoscopic cholecystectomy & breast surgery
  • Without prophylaxis risk of proximal DVT in 1%, risk of fatal PE in 0.01%
  • Rx – TEDs, Early mobilisation

Moderate Risk

  • Surgery > 30min and age > 40 yrs without additional risk factors
  • Laparoscopic surgery
  • Additional risk factors present
    • Cardiac/ pulmonary disease
    • Malignancy
    • ATIII
    • Pro-thrombotic disorders
  • Risk of proximal DVT = 3%
  • Rx - TEDs, early mobilisation, pneumatic compression devices, Enoxaparin 40mg
  • Enoxaparin that night or at time-out, currently not recommended to continue post-discharge

High Risk

  • Surgery in patients > 40yr with recent hx DVT or PE

  • Extensive abdominal or pelvic surgery

  • Surgery for malignancy

  • Surgery of lower limbs

  • Paralysis/ Immobility of lower limbs

  • Additional risk factors present

    • Cardiac/ pulmonary disease
    • Malignancy
    • ATIII
    • Pro-thrombotic disorders

  • Risk of proximal DVT 6%

  • Rx - TEDs, early mobilisation, pneumatic compression devices, Enoxaparin 40mg

  • In very high risk may consider continuing Enoxaparin for 4 weeks post-discharge

  • Exception

    • Not for 8 hrs post-epidural (and withhold for 24 hrs before withdrawing epidural & can be started 2 hours after)
      • NB: No evidence to support this

  • Dose Adjustment

    • Renal dysfunction (CrCL < 30) & < 40kg – Half dose to 20mg
    • BMI > 50 – Enoxaparin 60 mg

Fate of Thrombosis

  • Fate
    • Propagation
    • Embolization
    • Dissolution
    • Organisation & recanalization
  • Type
    • Primary Platelet Thrombus
      • In response to endothelial injury
      • Some fibrin deposition
    • Coralline Thrombus
      • Alternate pale (platelet) and dark (RBC and WBC) layers
      • Platelet laminae form the lines of Zahn
    • Occluding Thrombus
      • Coralline thrombus occludes the vein
      • Firmly attached; initial thrombus is white and firm
    • Consecutive Thrombus
      • Back to the next tributary
      • Consecutive thrombus is red (fibrin and entrapped red cells)
      • Loosely attached and prone to break off
      • If clot stops at the tributary, then further platelet thrombus is necessary before further red thrombus is formed (successive layers)
    • Propagating Thrombus
      • Red thrombus that continues beyond the next tributary
      • Eventually organisation and recanalisation occur
      • Thrombophlebitis associated with inflammation, therefore thrombus adherent to the intima and embolization rare

Clinical

  • 50% no clinical signs

  • ~ 50% local calf tenderness or a positive Homan’s sign do not have a DVT
    • Signs
      • Mild oedema to swelling of calf (> 2cm asymmetry)
      • Localised calf tenderness
        • Homan’s Sign – Calf pain following dorsiflexion of foot
      • Direct thrombus palpation
        • Most likely to be positive in the popliteal fossa
    • Phlegmasia Alba dolens
      • Painful white swollen leg, thrombosis of Iliac/ Femoral Veins
    • Phlegmasia Cerulea dolens
      • Severe pain with cyanosis of limb, sudden complete venous occlusion of the entire limb outflow, venous gangrene may occur with a 50% amputation rate
    • Superficial venous dilatation - decreased venous outflow causing congestion

Investigation

Wells Score DVT

Wells Score PE

  • D-dimer – High NPV, useless if recent surgery
  • Doppler USS
    • Investigation of choice
    • Consider proximal vs whole leg USS
  • Contrast enhanced CT venograph or MR venography
    • Alternative but rarely used

Treatment

  • Aims of treatment
  • Short term
    • Prevent extension, fatal PE and early recurrence
  • Long term
    • Prevent delayed recurrence, post-phlebitic syndrome and Pulmonary HTN

Anticoagulation

  • Clotting cascade Recap
  • Anticoagulants
  • LMWH v UFH
    • For treatment of proximal DVT have shown equal efficacy
    • At the appropriate dose there is no increase in the rate of significant clinical bleeding
    • Decreased risk of thrombocytopenia (HIT), occurs in up to 10% with UFH
    • Doses
      • Enoxaparin 1mg/kg bd
      • Fragmin 100U/kg bd or 200U/kg once daily
  • Treatment
    • If risk factor identified & reversible – 3 months
    • If idiopathic – 6-12 months
    • If irreversible risk factor or event was life threatening – permanent
    • Second episode – permanent
  • Options
    • Warfarin
    • Dabigatran
    • Rivaroxaban

Role of Surgery

  • Indications
    • Massive thrombosis causing compromised arterial circulation in the leg
      • Phlegmasia cerulea dolens
      • Massive iliofemoral DVΤ
      • Patients who fail therapeutic аոtiϲοаgulatiοո
    • Large DVT when standard treatment is absolutely contraindicated

Thrombolytic Therapy

  • Catheter-Directed Thrombolysis (CDT)
      - Uses local infusion of thrombolytics (e.g. tPA) directly into the thrombus
      - Often combined with mechanical thrombectomy
  • Pharmacomechanical Thrombectomy
      - Combines thrombolysis with mechanical clot disruption/removal
      - Used in conjunction with CDT for high clot burden
  • Surgery used when immediate resolution of the problem necessary
    • If more time then thrombolytic treatment
    • Use for a massive DVT in a younger person (less post-phlebitic syndrome)
    • Not for routine use with proximal thigh DVT
  • More rapid reduction in thrombus size
  • Significantly more bleeding (14%, OR 3.8) vs heparin
  • No evidence that short term response to treatment is clinically any better
    • However 3 of 4 studies showed decrease in post phlebitic limb syndrome
  • Do not use if thrombus is > 72 hours old (OTS suggests potential increased embolization)

Surgical Thrombectomy

  - Rarely used; considered when thrombolysis is contraindicated or fails
  - Involves open removal of clot from femoral or iliac veins
  - Often followed by fasciotomy if compartment syndrome is present

Filters

  • Filters/Interruption of IVC flow (Greenfield Filter)
    • Suprarenal placement
    • Retrievable filters now available
  • Prevents PE
  • Indications
    • Embolization happens while on optimal Rx
    • Anticoagulation contraindicated
      • e.g recent surgery, hemorrhagic stroke, active blееding
    • Large, proximal non-adherent thrombi
    • Not indicated for routine proximal DVT
  • NEJM 1998.
    • Randomised proximal DVT to filter or no filter as well as anticoagulation. Filters decreased PE in the first 2/52 (1% v 5%), but at 2 years the filter group had a higher rate of recurrent DVT (21% v 12%). No difference in mortality. So the initial benefit was counterbalanced by an increase in later DVT.
  • Complications
    • Can be serious
    • Migration to IVC bifurcation, iliac vein, renal vein, RA, RV, pulmonary artery
    • Protrusion through caval wall
    • Thrombus formation on filter
    • Thrombus formation above the filter (emboli)
    • Misplacement
    • Retroperitoneal haemorrhage
    • Perforation of Duodenum
    • Perforation of Ureter

Complications of DVT

  • Pulmonary embolis
    • SOB, chest pain, haemoptysis, pleural rub
    • S1Q3T3
  • Post-thrombotic Syndrome
    • Risk higher with recurrent & proximal DVT
    • Due to residual outflow obstruction with eventual calf muscle pump failure

Isolated Calf DVT

  • For a calf DVT > 5cm - 15-20% will extend if left untreated
  • Small DVT’s can be treated by compression (TED’s) and mobilization if duplex sonography done every 2 days or so to exclude extension
  • Treatment with LMWH is mandatory if extension occurs
  • As easy and as safe to Rx all lesions with ambulatory LMWH

Acute Iliofemoral Thrombosis

  • Investigate with Duplex, sometimes venography/ contrast CT to identify upper extent
  • Much higher risk of PE
  • Always anti coagulate
  • Consider thrombolysis in the younger patient

Subclavian Vein / Upper Limb Thrombosis

  • 2-3% of DVTs
  • Usually minimal venous stasis in upper limb
  • Subclavian 75%, Axillary 50%, Jugular 25%

Aetiology

  • Upper limb activity with direct or indirect injury to the vein
  • Occurring mainly at the thoracic outlet
    • 70% on dominant side
  • Classification
  • Secondary
    • Venous injury by indwelling CV catheter, external trauma, or pacemaker wires
    • Thoracic outlet syndrome / External compression (Lung malignancy – Pancoast tumour)

Risk Factors

  • Thoracic Outlet Syndrome
  • Metastatic tumour in the axilla – if can’t find a cause – look for a malignancy
  • Indwelling catheters
  • External trauma
    • Paget-Schroetter Syndrome

    • 50% of cases

    • Repetitive constriction of Subclavian Vein in Costoclavicular space (e.g. swimming) causing upper limb DVTs
    • Common to have anatomic anomalies such as cervical rib (may need to surgically excise) or myofascial bands
    • Thrombosis occurs in the dominant arm in 80% of cases

Clinical

  • Oedema/swelling within 24hrs of injury (95%)
  • May affect breast
  • Pain/aching (80%) in the limb and axilla
  • Examination
    • Swollen hand may have obvious venous engorgement
    • Cyanotic extremity
  • Collaterals over shoulder and anterior chest
  • 1/3 has a tender palpable cord in the axilla
  • SVC syndrome if clot extends there – face/neck swelling, periorbital oedema, blurred vision, facial cyanosis
  • Check for Cervical rib

Investigations

  • Duplex USS
  • Venography (rarely used)
  • Thrombophilia screen tests (preferably taken before anticoagulation started)
  • CT – may detect subclavian stenosis / thoracic outlet syndromes
  • MRI

Management

  • Rest
  • Elevate limb
  • Physio
  • Anticoagulation: Aim for INR 2-3 for 3-6 months then aspirin indefinitely afterwards
  • Consider thrombolysis in Paget-Schroetter if Sx < 2 weeks (Urokinase / tPA)
  • Catheter-directed thrombolysis ± followed by thoracic outlet decompression ± venous reconstruction / stent
  • Surgical bypass only if Sx are severe

Prognosis

  • Residual symptoms in 60-85%, residual oedema in about 40%
  • Recurrence 2%
  • PE as high as 12%

DVT prophylaxis

Mechanical

  • Early mobilisation
  • Compression
    • Stockings/TEDs
      • Simple, safe
      • 68% reduction in moderate risk
    • Devices - Pneumatic compression of calves during surgery
      • Proven to increase flow in the veins 180% for calf boots
      • Contraindicated with PVD
      • Thought to be effective in moderate risk general surgery

Pharmacological

  • Anticoagulants
  • A no. of studies have shown a decrease in DVT, esp. when measured with labelled fibrinogen
    • 9 RCTs comprising 1505 patients show a risk reduction of 64% in DVT diagnosed on I-125 fibrinogen uptake in low risk patients
  • Less clear if an equivalent decrease in PE
  • Heparin
    • 5000U BD, start preop, continue until ambulant
    • Study involving > 4000 pts showed 70% reduction in DVT, 47% reduction in PE, 66% reduction in fatal PE.
    • Main risk: Increased haemorrhage: increased risk of “excessive bleeding” or transfusion of 50-66%, overall increase of 2%
  • LMWH
    • Studies comparing Heparin and LMWH generally show a similar efficacy against DVT & PE, but have a lower rate of wound haematomas and re-operations for bleeding
  • Warfarin
    • Reduction of 66% in DVT and 80% in PE
    • Risk of severe haemorrhage of 2-7%
  • Dextran
    • Glucose polymer of 40 000 or 70 000 MW
    • Anti-platelet effect, decreases blood viscosity in deep veins
    • IV infusion 500-1000ml before surgery and at on alternate days after surgery until mobile
    • DVT risk 30-40%
    • Bleeding problems are reported. Decrease in fatal PE from 0.7% to 0.2%
  • Platelet-related - Aspirin and Dipyridamole
    • Aspirin decreased DVT from 20.4% to 12.5%
    • Meta-analysis suggests aspirin is useful
  • Epidural
    • Lumbar epidural with local anaesthetic increases lower limb blood flow, enhances fibrinolytic activity (by iPAI1), decreases platelet aggregation
    • In a series of hip replacement patients proximal DVT reduced by 2.5-5x & PE reduced by 3x

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