Updated: 6/21/2022

Thromboembolism (PE & DVT) Prophylaxis

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  • Summary
    • Venous thromboembolism (VTE) includes both pulmonary embolism (PE) and deep venous thrombosis (DVT)
    • Diagnosis is generally made with clinical exam and imaging to include ultrasound for extremity DVT and CT chest for pulmonary embolism
    • Treatment is pharmacologic blood thinners 
  • Epidemiology
    • Incidence
      • incidence
        • DVT
          • 200,000 per year in the US
        • PE
          • 50,000 per year in the US
    • Risk factors 
      • Virchow's triad
        • venous stasis
        • hypercoagulable state
        • intimal injury
      • primary hypercoagulopathies (inherited)
        • MTHFR/C677T/TT gene mutation carries the highest risk
        • factor V Leiden mutation
        • antithrombin III deficiency
        • protein C deficiency
        • protein S deficiency
        • activated protein C resistance
        • elevated factor VIII
        • hyperhomocysteinemia
        • prothrombin II G20210A
      • secondary factors (acquired)
        • malignancy
          • recently been associated with up to 20% of all new diagnoses of VTE
        • elevated hormone conditions
          • recombinant erythropoeitin
          • hormone replacement
          • oral contraceptive therapy
          • late pregnancy
        • elevated antiphospholipid antibody conditions
          • lupus anticoagulant
          • anticardiolipin antibody
        • medical history
          • history of thromboembolism
          • obesity
          • CHF
          • varicose veins
          • smoking
          • increased blood viscosity
          • thoracic outlet syndrome (upper extremity DVT)
        • other
          • general anesthetics (vs. epidural and spinal)
          • rapid increase in INR following unopposed initiation of warfarin therapy in arthroplasty patients
            • hypothesized to occur due to the warfarin-induced decline in protein C occurring before warfarin's antithrombotic effect occurs (protein C has a half-life of 6-8 hours and factor II has a half-life of 48-120 hours).
      • no increase in DVT has been associated with the use of tranexamic acid (TXA)
      • increasing incidence of pediatric VTE due to obesity, contraceptives, smoking, etc.
  • Etiology
    • Pathophysiology
      • Mechanism of clot formation
        • stasis
        • fibrin formation
          • thromboplastin (aka Tissue Factor (TF), platelet tissue factor, factor III) is released during dissection which leads to activation of the extrinsic pathway and fibrin formation
        • clot retraction
        • propagation
  • Anatomy
    • DVT usually begins in venous valve cusps.
    • Thrombi consist of thrombin, fibrin, and RBCs with relatively few platelets.
  • Classification
    • Acute DVT
      • clots are developing or have recently developed within 28 days
    • Chronic DVT
      • persists more than 28 days
      • an episode of VTE after an initial one is classified as recurrent.
  • Presentation
    • Symptoms of DVT
      • calf pain
      • palpable cords
      • pitting extremity swelling
        • 50% with classic signs have no DVT
    • Symptoms of PE
      • most PEs are asymptomatic     
      • symptoms
        • pleuritic chest pain                             
        • dyspnea                              
        • tachypnea                                
        • large PEs (e.g., saddle emboli) can present as death though
  • Imaging
    • Radiographs
      • recommended views
        • 2 view chest (PA and lateral)
      • findings
        • early findings
          • usually normal but may present with
            • “oligemia” 
            • prominent hilum 
        • late findings
          • wedge or platelike atelectasis 
    • Duplex compression ultrasound
      • recommended views
        • should be ordered on the extremity of concern 
        • gold standard for diagnosis of DVT
      • findings
        • "noncompressible vein"
          • 95% sensitive/specific
        • 50% with venogram positive for clot have normal physical findings 
        • no indication for routine duplex screening
    • CT pulmonary angiography
      • indications
        • gold standard for diagnosis of PE
    • Ventilation-perfusion scan
      • indications
        • helpful for contrast-allergy patients
  • Studies
    • Labs
      • d-dimer
        • can be helpful in ruling out a significant clot.
        • not as helpful after injury/surgery  
    • EKG
      • indication
        • rule out MI
      • findings
        • most common finding is sinus tachycardia.
  • Treatment
    • Prophylaxis
      • indications
        • prevention of deep vein thrombosis (DVT) and pulmonary embolism (PE) is most important factor in decreasing morbidity and mortality
        • the use of pharmacologic prophylaxis and mechanical compression received a moderate strength recommendation from the AAOS
        • prophylaxis treatment should be determined by weighing risk of bleeding vs risk of pulmonary embolus
          • AAOS risk factors for major bleeding
            • bleeding disorders
            • history of a recent gastrointestinal bleed
            • history of a recent hemorrhagic stroke
          • AAOS risk factors for pulmonary embolus
            • hypercoagulable state
            • previous documented pulmonary embolism
          • DVT prophylaxis is recommended for all hip/knee arthroplasty patients 
          • For standard patients, DVT prophylaxis is NOT recommended for following
            • upper extremity procedures
            • arthroscopic
            • isolated fractures at knee and below
    • Treatment of VTE
      • serial US scans
        • indications
          • isolated calf thrombosis smaller than 5 cm rarely needs treatment.
      • pharmacologic treatment
        • duration
          • approximately 3 months after DVT
          • approximately 12 months after PE
      • early mobilization
        • risk of dislodgment less than risk of more clots in these high-risk patients
      • graduated elastic compression hose 
        • may prevent postthrombotic syndrome
      • thrombolytics, thrombectomy, embolectomy
        • indications
          • controversial
  • Techniques
    • Pharmacologic agents
    • Hip & Knee Arthroplasty Prophylaxis
      • indication
        • VTE prophylaxis recommended for all THA and TKA patients
          • AAOS and American College of Chest Physicians developed guidelines but do not recommend an optimal regimen; an individualized ppx regimen balancing efficacy and safety based on risk factor should be implemented
      • techniques
        • mechanical prophylaxis
          • compressive stockings recommended
          • pneumatic compression devices are recommended by the AAOS across all risk (low to high risk of either bleeding or pulmonary embolism) groups undergoing total hip or total knee arthroplasty
            • increase venous return and endothelial-derived fibrinolysis
            • decrease venous compliance and venous stasis
        • chemoprophylaxis
          • American Academy of Orthopaedic Surgeons (AAOS) and American College of Chest Physicians (ACCP) support ASA as a monotherapy
    • Spine Surgery Prophylaxis
      • indication
        • no clear consensus regarding utilization or timing of VTE prophylaxis measures after spine surgery
        • risks of VTE must be weighed against postoperative bleeding and epidural hematoma formation
        • patients with a spinal cord injury and prolonged immobilization are at increased risk
      • technique
        • early mobilization is recommended, along with pneumatic compression devices
        • chemoprophylaxis
          • longer surgical times
          • multilevel thoracolumbar surgery
          • anterior thoracolumbar approaches
    • Shoulder Arthroplasty Prophylaxis
      • indication
        • early mobilization, mechanical prophylaxis, regional anesthesia
        • LMWH/heparin until ambulatory if increased risk, not for routine use in UE surgery
    • Foot & Ankle Surgery Prophylaxis
      • the risk of VTE was not found to be lowered by thromboprophylaxis in a study of 20,043 adult patients
    • Trauma prophylaxis
      • mechanical and chemoprophylaxis lower the rate of DVT and PE
  • Complications
    • DVT complications
      • pulmonary embolism (PE)
      • chronic venous insufficiencypost-thrombotic syndrome.
      • post-thrombotic syndrome.
        • incidence
          • post-thrombotic syndrome occurs in 43% two years post-DVT (30% mild, 10% moderate, and severe in 3%). 
    • PE complications
      • sudden cardiac death
      • obstructive shock
      • pulseless electrical activity
      • atrial or ventricular arrhythmias
      • secondary pulmonary arterial hypertension
      • cor pulmonale
      • severe hypoxemia
      • right-to-left intracardiac shunt.
    • Recurrence
      • incidence 
        • risk of recurrence of DVT is 25%.
  • Prognosis
    • Many DVTs will resolve with no complications.
    • Death occurs in
      • 6% of DVT cases within 1 month of diagnosis
      • 12% of PE cases within 1 month of diagnosis.
    • Approximately 10% of patients who develop PE die within the first hour, and 30% die subsequently from recurrent embolism.

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(SBQ16HK.18) Which of the following is true regarding venous thromboembolism (VTE) following major orthopaedic hip or knee surgery?

QID: 211306

Almost all patients receive VTE prophylaxis, though often not in compliance with the American College of Chest Physicians (ACCP) guidelines

36%

(745/2079)

Length of hospitalization and associated medical costs are significantly increased by in-hospital VTE but not post-discharge VTE

5%

(104/2079)

Most acute perioperative pulmonary events result from dislodged chronic deep venous thrombosis resulting in pulmonary embolism

10%

(201/2079)

Most symptomatic VTE occur within two weeks after total joint arthroplasty

45%

(945/2079)

Warfarin prophylaxis is more often fully compliant with ACCP guidelines than low-molecular-weight heparin (LMWH) prophylaxis

3%

(61/2079)

L 5 B

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(OBQ13.244) A 59-year-old patient undergoing total hip arthroplasty has a genetically inherited thrombophilia disorder. In this disorder, a variant co-factor cannot be inhibited by activated protein C causing overproduction of thrombin. What is this patients clotting disorder?

QID: 4879

Factor V Leiden

71%

(2841/3997)

Antithrombin III deficiency

12%

(484/3997)

Familial dysfibrinogenemia

2%

(97/3997)

Protein S deficiency

12%

(487/3997)

Congenital deficiency of plasminogen

1%

(50/3997)

L 3 B

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(OBQ12.206) A 52-year-old male underwent a right total knee arthroplasty 3 days ago and reports new onset dyspnea. His vitals signs include a temperature of 98.8, pulse of 133, blood pressure of 130/77, respiratory rate of 28, and oxygen saturation of 91% on room air. A chest radiograph shows atelectasis. Which of the following findings is most likely also present?

QID: 4566

Hyperchloremic metabolic acidosis

8%

(328/4215)

Jugular venous distention with tracheal deviation

4%

(158/4215)

EKG demonstrating S-wave in lead I Q-wave in lead III T-wave inversion in lead III

73%

(3076/4215)

Pleural effusion with pleural/serum protein >0.5 and pleural/serum LDH > 0.6

5%

(211/4215)

Increased carbon monoxide diffusing capacity (DLCO)

9%

(398/4215)

L 2 D

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(OBQ10.189) A 30-year-old male with Protein C deficiency sustains a large subarachnoid hemorrhage and bilateral calcaneus fractures after falling off of a roof. The patient has been in the intensive care unit for 5 days for monitoring of his head injury. All of the following factors are appropriate reasons to obtain a helical chest CT scan EXCEPT:

QID: 3282

Elevated alveolar-arterial gradient (> 20 mm Hg or 2.7 kPa) on arterial blood gas

9%

(317/3402)

Pulse oximetry reading of 99% with respiratory rate of 35 breaths/min

29%

(987/3402)

Pulse rate of 125 beats/min with new onset right bundle branch block

9%

(323/3402)

Paco2 > 35 mm Hg (or 4.7 kPa) on arterial blood gas

46%

(1548/3402)

Pao2 < 80 mm Hg (or 10.7 kPa) on arterial blood gas

6%

(199/3402)

L 4 D

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(OBQ10.67) A 67-year-old man complains of low-grade fevers and calf pain 2 weeks following a total knee arthroplasty. What is the next appropriate step in management of this patient?

QID: 3154

Plethysmography of lower extremity

1%

(21/3168)

MRI of lower extremity

0%

(10/3168)

CT angiography of lower extremity

1%

(36/3168)

Venous ultrasonography

94%

(2976/3168)

Knee aspiration to evaluate for septic joint

4%

(118/3168)

L 1 C

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(OBQ09.265) The 2009 AAOS Clinical Guideline on prevention of pulmonary embolism in patients undergoing total hip or knee arthroplasty recommends classifying patients as having either a "standard" or "elevated" risk of bleeding complications. The presence of all of the following qualify a patient as having an "elevated" risk of major bleeding EXCEPT?

QID: 3078

History of hemophilia

2%

(33/1978)

History of protein C deficiency

80%

(1575/1978)

History of a recent gastrointestinal bleed

8%

(157/1978)

History of a recent hemorrhagic stroke

4%

(82/1978)

History of Von Willebrand's Disease

6%

(122/1978)

L 1 C

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(OBQ08.144) Which of the following is NOT a component of Virchow's triad?

QID: 530

Thrombocytopenia

8%

(137/1807)

Platelet dysfunction

3%

(49/1807)

Hypercoagulability

1%

(13/1807)

Venous stasis

2%

(28/1807)

Neither thrombocytopenia (answer 1) nor platelet dysfunction (answer 2) are components of Virchow's triad

87%

(1576/1807)

L 1 D

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(SBQ07HK.4.1) In 2012, the American College of Chest Physicians (ACCP) brought forth changes to their guidelines on postoperative pharmacologic venous thromboembolism prophylaxis (VTEP) after total joint arthroplasty in order to converge with the American Academy of Orthopaedic Surgeons (AAOS). Which of the following describes the change in surgeon practice patterns following the convergence of these guidelines?

QID: 9116

An increase in the prescribing of ASA (aspirin) monotherapy

77%

(1293/1670)

An increase in the prescribing of coumadin at INR goals of 2-3

2%

(35/1670)

An increase in the prescribing of low-molecular-weight heparin monotherapy

17%

(280/1670)

An increase in the use of elastic compressive stockings as monotherapy

3%

(44/1670)

An increase in the prescribing of fish oil as monotherapy

0%

(6/1670)

L 2 C

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(SAE07HK.61) Familial (Leiden) thrombophilia is of importance in joint arthroplasty because of an abnormality in the clotting cascade. Which of the following statements best describes the condition?

QID: 6021

It is a disease caused by an abnormality of platelets that leads to increased blood clotting.

4%

(15/423)

It is a disease caused by an abnormality of vascular endothelium that leads to increased blood clotting.

3%

(12/423)

It is a disease caused by an abnormality of hepatic metabolism that leads to decreased production of factor V and decreased blood clotting.

4%

(19/423)

It is a disease caused by an abnormality of factor V that leads to decreased inactivation of factor Va by activated protein C (aPC) and increased blood clotting.

87%

(369/423)

It is a familial, genetic disease that requires placement of a Greenfield filter in all individuals who have the abnormality, prior to surgery.

0%

(2/423)

L 1 E

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(OBQ05.27) During total hip arthroplasty, which of the following interventions increases the risk of pulmonary ventilation-perfusion mismatch the greatest?

QID: 64

Acetabular reaming

3%

(66/2208)

Cement pressurization of the femoral canal

94%

(2066/2208)

Use of a modular femoral stem

1%

(33/2208)

Intra-operative sequential compressive device on the non-operative leg

1%

(15/2208)

Posterior approach

1%

(20/2208)

L 2 C

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(OBQ05.172) A 65-year-old man undergoes total knee replacement and is found to have deep vein thrombosis two days later. What molecule is thought to be involved in this process when it is released during surgical dissection?

QID: 1058

Prothrombin

38%

(802/2137)

RANKL

1%

(28/2137)

IL-1b

12%

(258/2137)

Thromboplastin

45%

(954/2137)

Factor XI

4%

(88/2137)

L 4 D

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(OBQ04.224) A 25-year-old healthy male is scheduled to undergo a a nine-level posterior spinal fusion for scoliosis. Administering preoperative recombinant erythropoietin would place the patient at increased risk of developing which of the following complications?

QID: 1329

Acute renal failure

6%

(59/969)

Increased bleeding time

5%

(49/969)

Thrombotic event

80%

(780/969)

Wound complications

3%

(33/969)

Delayed spinal fusion

4%

(43/969)

L 2 D

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(OBQ04.273) A 65-year-old female undergoes a total knee arthroplasty. In addition to chemoprophylaxis for deep vein thrombosis (DVT) prevention she is given pneumatic compression devices. Which of the following is associated with pneumatic compression devices?

QID: 1378

Increased endothelial fibrinogenesis

5%

(57/1122)

Decreased bleeding times

0%

(3/1122)

Increased endothelial injury

2%

(27/1122)

Increased venous compliance

10%

(108/1122)

Increased venous blood flow

82%

(924/1122)

L 2 C

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