DVT / PE

• synonyms: deep vein thrombosis, pulmonary embolism, venous thromboembolic disease (VTD)
• ICD-9=
• Fatal PE rates of 1% to 3% of untreated patients undergoing joint replacement and asymptomatic PE rates of 10% to 15% have traditionally been sited. More recent reports suggest that the rate of Fatal PE is 0.1% to 0.2%. These rates may be unaffected by thromboprophylaxis. (Simon SR, Ortho Basic Science, 2nd p223)
• Fatal PE rate after primary TKA for patients who did not recieve prophylaxis, but did have short operative times and rapid mobilization = 0.1%, 1.1% for symptomatic DVT. (Warwick D, JBJS 1997;79A:780)
• Coagulation Cascade: Both Intrinsic and Extrinsic pathways lead to the formation of factor X which then leads to the eventual development of Fibrin.
• Intrinsic pathway: monitored by PTT, inhibited by heparin.
• Extrinsic pathway: monitored by PT, inhibited by warfain.

DVT / PE Risk Factors

• History of DVT
• Immobilization
• Paralysis
• Obesity
• Malignancy
• Elderly
• Congestive Heart Failure / History of MI
• Pregnancy
• Estrogen use or hormone replacement therapy (Oral Contraceptives)
• Varicose Veins
• Smoking
• Virchow's Triad: venous stasis, hypercoagulability, intimal injury
• General Anesthesia (lower risk with epidural anesthesis)
• Blood transfusion
• Antithrombin III deficiency
• Protein C deficiency
• Protein S deficiency
• Activiated protein C reistance
• Bed rest / immobility > 5 days
• Fracture (pelvic, hip, femur, tibia)
• History of stroke
• Inflammatory bowel disease
• Multitrauma
• Major surgery

DVT Clincal Evaluation

• Pain and swelling in affected extremity, palpable cord.
• Homan's sign
• Physical exam specificity and sensitivity are <50%. ((Simon SR, Ortho Basic Science, 2nd p314)

DVT Xray

• Venography: gold standard, invasive exposes patient to radiation.
• Duplex Ultrasound: non-invasive, technician and radiologist dependent.
• Doppler Ultrasound:
• Fibrinogen I 125 labeling and impedance plethysmography have low specificity and sensitivity and are generally no longer used.

DVT Prophylaxis

• No prophylactic agent has been associated with a significantly different risk for fatal PE. (Freedman KB, JBJS 2000;82A:929)
• DVT Prophylaxis recommendations: Patients without significant risk factors for DVT should be given aspirin, Ted hose and ICD's post-operatively and discharged on aspiring for 6weeks. Patients with risk factors (previous DVT, postoperative ileus) should be begin with SQ LMWH and then switched to oral warfin for 8weeks.
• Prophylaxis options: Coumadin, LMWH, Aspirin

DVT Classification / Treatment

• Treatment is indicated for all DVTs proximal to the knee. Treament for DVT below the knee is controversial.
• Heparin followed by conversion to long-term warfarin (usually 3 months).
• Consider direct intraclot lacing of the thrombus with alteplase (maximum daily dose, 50 mg per leg per day; maximum of four treatments) and full systemic anticoagulation. (Chang R, Radiology 2008;246:619).
• Preoperative diagnosis of DVT in a patient with lower extremity/pelvic DVT: vena cava filter

PE Clinical Evaluation

• Dyspnea, pleuritic chest pain, tachypnea (90%), tachycardia (60%), rales, pyrexia hemoptysis.

PE Xray

• EKG: right-bundle branch block, right axis deviation, ST depression, T wave inversion in lead III. EKG changes occur in 25%, usually with large embolization.
• CXR: generally normal, may show hyperlucency, or enlarged hilar artery. Non-specific findings = pleural effusion, etatlectasis, elevated hemidiaphragm.
• ABG: Findings are nonspecific. PO2 < 60mmHg is highly suggestive of repiratory distress. Normal PO2 does not exclude PE.
• V/Q scan: most commonly used. Indeterminate scans must be followed with spiral CT/pulmonary angiography or duplex ultrasound.
• Pulmonary angiogram: Gold standard, invasion
• Spiral CT: 70% sensitivity, 88% specificity.

PE Classification / Treatment

• Continous IV heparin for 7-10 days, monitored by PTT(maintain between 60 and 80 sec). Convert to 3 months of oral warfarin (maintain INR at 3.0).
• Alternative treatment: LMWH

Warfarin (Coumadin)

• Blocks hepatic enzymes (vitamin K epoxide, possilbly vitamin K reductase) leading to decreased carboxylation of vitamin K-dependent factors II, VII, IX, X.
• Fatal PE rate = 0.15%: 1%-5% risk for bleeding complications. (Brookenthal KR, J Arthroplasty 2001;16:293)
• Requires monitoring with PT (Prothrombin time)
• Contraindicated in patients with PUD, GERD, liver insufficiency, alcoholism, uncontrolled hypertension, pregnancy, patients on NSAIDS or history of bleeding disorders.
• The current recommended dosing protocol maintains INR at 1.8 to 2.5.
• Reversed with vitamin K or fresh frozen plasma.
• 1%-5% local or systemic bleeding incidence.
• Multiple drug reactions: rifampin, trimethoprim, cimetidine, phyentoin, cefamandole and phenobarbital are antagonists to warfarin.
• Increased gastric ulcer bleeding risk if used with NSAIDs

Low-Molecular Weight Heparin

• Enoxaparin (Lovenox), dalteparin
• Prevents binding of antithrombin to thrombin. Selectively tagets Factor Xa
• No monitoring needed.
• Use sparingly in patients with renal impairment (metabolized in the kidney)
• Generally considered to provide least rate of radiographically proven DVT, but does not reduce the rate of fatal PE compared to other methods and has significanlty higher bleeding complications, up to 12%.

Aspirin

• Inhibits thromboxane-A2 synthesis by irreversibly inhibiting cyclooxygenase (COX)
  in platelets as well as megakaryocytes.
• Aspirin alone proximal DVT rate = 12-15%, fatal PE rate = 0.2%. (Freedman KB, JBJS 2000;82A:929)
• Fatal pulmonary embolism = 0.13 percent, nonfatal pulmonary embolism = 0.94 percent, DVT = 1.01. (Sarmiento A, JBJS 1999;81A:339)
• Contraindications: hypersensitivity to aspirin, previous DVT, chronic venous stasis, PUD, disorders affecting platelet function
• Dosage: aspirin suppository (600 milligrams) immediately after operation followed by 325 milligrams of aspirin twice a day until discharge. Should always be used with graded elastic stockings (Ted hose) and/or intermittent compression devices (Sarmiento A, JBJS 1999;81A:339)
• Generally continued for 6-8weeks post-operatively

Heparin

• Binds antithrombin III causing a conformational change in its structure exposing its active site (arginine). This increases antithrombin IIIs affinity for clotting factors, namely thrombin and Xa, leading to decreased clot formation.
• Fixed low-dose heparin (5,000 U Q 8 to 12 hours) is ineffective in orthopeadic patients.
• Adjusted-dose heparin (maintain PTT of 31.5 - 36 sec) requires monitoring several times per day and frequent dose adustment with a significant rate of wound hematoma, up to 24%,
• Alternative anticoagulation methods with fewer bleeding complications are generally used.

Fondiparinux

• Direct factor Xa inhibitioin which inhibits fibrin formation
• associated with the highest bleeding complications. (Turpie AG, Lancet 2002;359:1721)
• Fondaparinux 2.5mg SQ QD starting the morning after surgery.
• Contraindicated in renal failure patients.

Intermittent Compression Devices

• Pulmonary Embolism 0.6%, DVT incidence = 4.6% (Hooker JA, JBJS 1999;81A:690)
• No risk of bleedig complications.

Vena Cava Filter

• Indications: recent symptomatic PE, known DVT, significant contraindication to anticoagulation.