Updated: 5/27/2019

Pulmonary Thromboembolism

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Introduction
  • Pulmonary embolism as seen by CT. The white arrows highlight the filling defects of IV contrast.Defined as occlusion of a pulmonary artery from embolization of a thrombus from a distal site
    • size of embolism determines proximity of occlusion to pulmonary trunk
      • Saddle embolus
        • large clot that occludes central pulmonary arteries
    • most commonly due to a thromboembolism from the deep veins of the leg
      • highest number originate from femoral vein
  • Risk factors
    • Virchow's triad
      • stasis
        • immobility
        • CHF
        • obesity
        • surgery
      • hypercoagulability
        • pregnancy
        • OCP
        • protein C/S deficiency
        • factor V Leiden
        • severe burns
        • cancer
      • endothelial damage
        • exposed collagen stimulates clotting cascade
          • trauma
          • fracture
          • previous DVT
Presentation
  • Dyspnea and tachycardia common presenting findings
  • May see hypoxemia on pulse oximetry and ABG
    • ABG often shows ↓ PO2↓ PCO2↑ A-a gradient 
  • Pleuritic chest pain
  • Sudden death
    • acute right heart failure from rapid increase in pulmonary artery pressure
    • more common with saddle embolism
  • Pleural friction rub
  • Fever
    • if pulmonary infarct
  • Deep vein thrombosis
    • Homans' sign
      • dorsiflexion of foot leads to tender calf muscle
      • not present in the majority of cases (not sensitive or specific)
    • erythematous, swollen, warm, lower extremity
 
Imaging
  • Chest CT with angiography
    • test of choice in most circumstances
    • visualize filling defect in pulmonary artery
  • V/Q radionuclide scan
    • ↓ pulmonary perfusion without decreased ventilation to given area
    • used when patient cannot tolerate CT contrast (renal failure, pregnancy)
    • requires a normal chest xray to be useful
  • pulmonary angiogram
    • gold-standard confirmatory test
    • rarely used
Studies
  • Labs
    • serum D-dimers 
      • result of clot degradation
      • only useful if low pretest probability (Wells criteria)
        • high sensitivity but low specificity
Treatment
  • Pharmacologic
    • anticoagulation 
      • heparin or low-molecular weight heparin (LMWH)
      • warfarin
        • begin for long term anticoagulation
    • thrombolysis
      • in cases of hemodynamic compromise
  • Operative
    • inferior vena cava filter
      • indicatied if anticoagulation is contraindicated or if patient develops a PE while on  anticoagulants
    • thrombectomy
      • in cases of hemodynamic compromise and contraindication to thrombolytic therapy
  • Prevention
    • Subcutaneous heparin or LMWH most effective for immobile patients or patients at high risk
    • early ambulation as able
    • Sequential compression devices when pharmacologic prophylaxis is contraindicated
Complications
  • Pulmonary infarction
    • most cases do not result in infarction due to large degree of collateral circulation in the lungs
    • occur when patient has a reduction in pulmonary blood flow
      • secondary to decreased cardiac output or obstructive lung disease
  • Death
    • Due to right ventricular failure
 

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(M1.PL.13.20) A 73-year-old female is hospitalized following a pelvic fracture. She undergoes surgical repair without complication. Four days into her hospital stay, she develops acute dyspnea and chest pain accompanied by oxyhemoglobin desaturation. Which of the following arterial blood gas values is the patient most likely to have? (normal values: pH 7.35 - 7.45, PaO2 80 - 100 mm Hg, PaCO2 35-45 mm Hg, HCO3 22-26) Tested Concept

QID: 100823
1

pH 7.5, PaO2 60, PaCO2 30, HCO3 22

34%

(11/32)

2

pH 7.3, PaO2 60, PaCO2 30, HCO3 20

3%

(1/32)

3

pH 7.5, PaO2 60, PaCO2 50, HCO3 28

12%

(4/32)

4

pH 7.3, PaO2 60, PaCO2 50, HCO3 24

38%

(12/32)

5

pH 7.4, PaO2 60, PaCO2 40, HCO3 24

6%

(2/32)

M 2 C

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(M1.PL.13.4) Four days after undergoing an elective total hip replacement, a 65-year-old woman develops a DVT that embolizes to the lung. Along with tachypnea, tachycardia, and cough, the patient would most likely present with a PaO2 of what? Tested Concept

QID: 100807
1

120 mmHg

3%

(1/38)

2

110 mmHg

5%

(2/38)

3

100 mmHg

13%

(5/38)

4

85 mmHg

8%

(3/38)

5

60 mmHg

71%

(27/38)

M 2 E

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