Pulmonary Thromboembolism

• • Deep venous thrombosis (DVT) most common source of pulmonary embolism (PE)

  • Uncommon causes of embolism include:

  • -Air (complications from central lines)

    -Fat (long bone fractures, respiratory insufficiency, coagulopathy, encephalopathy, petechiae)

    -Amniotic (during active labor)

    -Tumor emboli from RA or inferior vena cava (IVC)

  • < 10% of PE cause pulmonary infarction

  • Size and frequency of PE determines disease and outcome

  • PE obstructing large pulmonary artery: RV failure

  • PE causes release of vasoactive amines causing severe pulmonary vasoconstriction, increased dead space and hypoxia from right-to-left shunt

  • Reflex bronchial vasoconstriction common

Epidemiology

• • 50,000 deaths yearly in United States

  • Third leading cause of death in hospital patients

  • Only 30-40% have suspected DVT

  • PE develops in 60% of untreated proximal lower extremity DVT

Symptoms and Signs

• • Dyspnea and chest pain (present in 75%)

  • Tachycardia, tachypnea, altered mental status

  • Classic triad: Dyspnea, chest pain, hemoptysis (15%)

  • Pleural rub and S1Q3T3 rarely found

Laboratory Findings

• • ABG measurement: Hypoxia with respiratory alkalosis

  • ECG: New onset atrial fibrillation, ST/T wave changes, sinus tachycardia

  • Elevated D-dimer levels

Imaging Findings

• • Chest film: Often normal, may show pulmonary cap

  • ECG: May show atrial fibrillation, ischemic changes, or RV strain (S1Q3T3), but usually only sinus tachycardia.

  • V̇/Q̇ scan: Sensitivity & specificity of 90%, however, 67% of studies are inconclusive

  • Spiral CT: More accurate than V̇/Q̇ scan

  • Magnetic resonance angiography: Excellent sensitivity and specificity

  • Pulmonary angiogram: Invasive but gold standard

• • Evaluate for other causes of chest pain and hypoxia, such as pneumonia

  • Evaluation may be clouded by other possibilities including postoperative pneumonia, which can make V̇/Q̇ scan nondiagnostic

  • Spiral CT of chest most sensitive and efficient in postoperative patient

• • ABG measurement

  • Chest film

  • Duplex Doppler of lower extremity

  • V̇/Q̇ scan (often inconclusive), cannot be interpreted in face of abnormal chest film

  • Spiral CT of chest accuracy better than V̇/Q̇ and does not need clinical correlation

  • Magnetic resonance pulmonary angiogram

• • Initial stabilization with pressors and ventilatory support

  • Start heparin/low-molecular-weight heparin expediently

  • Consider thrombolytics if large clot burden, sever respiratory compromise, hemodynamic instability

Surgery

• • IVC filter

  • Open surgical thrombectomy: High mortality (Trendelenburg procedure)

  • Catheter-based suction embolectomy: only in experienced operators

  • Extracorporeal membrane oxygenation (ECMO) can be a last resort in a critical situation

Indications

• • IVC filter

  • -Contraindication to anticoagulation

    -Venous thrombosis extension on anticoagulation

  • Open pulmonary embolectomy

  • -Intractable hemodynamic instability

    -Thrombolytics inadequate or not available

    -Rarely indicated or useful

Prognosis

• • Preventable cause of hospital death

Prevention

• • DVT prophylaxis ...