PE is a complication principally affecting people with underlying disorders, such as cardiovascular disease or cancer. Immobilized patients are at much higher risk. PE is the sole or a major contributing factor in 10% of acute adult deaths in hospitals.
Over 95% of pulmonary emboli originate from deep vein thromboses, and its risk factors accordingly mirror those of thrombosis. These include:
Massive PE: main pulmonary arteries. Can have hypotension, presyncope, or syncope, with SOB.
Pulmonary embolism often presents with acute shortness of breath accompanied by chest pain, hemoptysis, severe hypoxemia, and circulatory collapse due to shock.
Often, however, signs and symptoms are much more subtle, with mildly increased dyspnea on exertion and atypical chest pain the only symptoms.
Physical exam may reveal sounds ranging from isolated crackles to diffuse wheezing. Pleural effusions may be present.
sudden onset
recent history of surgery or trauma
signs or symptoms of DVT
immobility
hypercoagulability
medications: oral contraceptives
General appearance: degree of respiratory distress or fever
Assess for DVT.
Identify pleural rubs, wheezes, crackles, or signs of pneumothorax.
Hypotension, tachycardia, tachypnea, fever
S1Q3T3
Chest X-ray can often show pulmonary infarction. Most cases are normal. A wedge-shaped area is strongly suggestive. Chest X ray is often normal but can show atelectasis, isolated infiltrates, or small pleural effusion. Abrupt cutoff of pulmonary vessels or enlarged central pulmonary arteries may also be present.
CT angiography (spiral CT) is useful for PE. Use contrast material, excuding those at risk of nephrotoxicity. Sensitive for main, lobar, and segmental arteries, but not subsegmental. Can also help identifty differential diagnoses. More specific than VQ scan.
V/Q scan. is a nuclear test. More sensitive, but less specific than spiral CT. Nucleotide injection peripherally and assess for areas of low perfusion. Step 2: Radionuclides inhaled, and lung fields assessed.
Tests reveals
If underlying lung disease, like COPD, makes tests less diagnostic.
Pulmonary angiography: dye injected just as they enter the CT. If patients have poor kidney function, or are allergic to dye, will not work.
Doppler compression ultrasound of legs is the most effective bedside test.
Echocardiography
Arterial blood gases
D-dimer is sensitive but not specific. It is useful in people with low pre-test probability.
If there is a high probability, not as useful, except to exclude PE.
Degradation product of cross-linked fibrin
FVL
Protein C and Protein S (though do not measure if on warfarin)
antithrombin III
prothrombin gene mutation
APLA, ACl-A, LAC
Differential diagnosis of PE includes:
Arterial blood gases may show acidemia, hypoxemia, and hypercapnia, but even sublte changes such as mild alkalosis may be present (why?) Elevated LDH can result from tissue infarction, but is neither sensitive nor specific.
Simplified Wells Clincial Model
V/Q scan compares lung ventilation with lung perfusion using radiolabeled tracer gas. Spiral CT and angiography can be used with certainty though attendant risks.
Doppler ultrasounds of the legs can be used to identify sites of thrombosis.
Once a clot dislodges from site of origin, it travels through the circulation until it becomes trapped in a pulmonary artery. The affected lung segment develops an increased ventilation/perfusion (V/Q) ratio, increasing dead space and leading to inefficient gas exchange.
Pulmonary infarction is rate due to collateral circulation and bronchial arteries.
PE can cause acute cor pulmonale.
PE is treated with supportive measures to sustain life. Mechanical removal of clots is difficult and dangerous, and medical treatments are used to dissolve existing clots and prevent future events.
Unfractionated heparin or low-molecular-weight heparin is started acutely for a minimum of 5 days. Initiate oral anticagulants such as warfarin on day 1. Heparin can be stopped once INR >2.0 for 24h. Patients can be treated as outpatients.
Thrombolytics can be used to existing clots. Indications:
Reasonable to do a thorough history and physical exam to examine for risk factors
There are risks and benefits to these.
Ambulation
Compression stockings
heparin and warfarin