Pulmonary Embolism (PE) PDF

2/22/24, 2:02 PM Realizeit for Student Introduction PE refers to the obstruction of the pulmonary artery or one of its branches by a thrombus (or thrombi) that originates somewhere in the venous system or in the right side of the heart. Deep vein thrombosis (DVT), a related condition, refers to thro...

2/22/24, 2:02 PM Realizeit for Student Introduction PE refers to the obstruction of the pulmonary artery or one of its branches by a thrombus (or thrombi) that originates somewhere in the venous system or in the right side of the heart. Deep vein thrombosis (DVT), a related condition, refers to thrombus formation in the deep veins, usually in the calf or thigh, but sometimes in the arm, especially in patients with peripherally inserted central catheters. VTE is a term that includes both DVT and PE. PE can be associated with trauma, surgery (orthopedic, major abdominal, pelvic, gynecologic), pregnancy, heart failure, age older than 50 years, hypercoagulable states, and prolonged immobility. It also may occur in apparently healthy people. In the United States, the precise number of people impacted by VTE is unknown; as many as 900,000 people could be affected each year (CDC, 2015e). One-third of people with a VTE will have a recurrence within 10 years. Estimates range that from 60,000 to 100,000 Americans die of VTE; 10% to 30% of people will die within the first month of diagnosis, and sudden death is the first clinical sign in about 25% of people who experience a PE (CDC, 2015e). The outcome in acute PE depends on the presence of preexisting comorbidities and the extent of hemodynamic compromise. Pathophysiology Most commonly, PE is due to a dislodged or fragmented DVT (see previous pathophysiology discussion in DVT). However, there are other types of emboli that may be implicated: air, fat, amniotic fluid, and septic (from bacterial invasion of the thrombus) (Norris, 2019). A PE is described as an occlusion of the outflow tract of the main pulmonary artery or of the bifurcation of the pulmonary arteries. Multiple small emboli can lodge in the terminal pulmonary arterioles, producing multiple small infarctions of the lungs. A pulmonary infarction causes ischemic necrosis of part of the lung (Thompson & Kabrhel, 2020). When a thrombus completely or partially obstructs a pulmonary artery or its branches, the alveolar dead space is increased. The area, although continuing to be ventilated, https://herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zSNYYvz6N%2bxRwegtqPK%2fJ7UsPJxuq7nE1D4sTAvq22Nk5Sl… 1/3 2/22/24, 2:02 PM Realizeit for Student receives little or no blood flow. Therefore, gas exchange is impaired or absent in this area. In addition, various substances are released from the clot and surrounding area that cause regional blood vessels and bronchioles to constrict. This results in an increase in pulmonary vascular resistance—a reaction that compounds the ventilation– perfusion (V./Q.) imbalance that ensues. The hemodynamic consequences are increased pulmonary vascular resistance due to the regional vasoconstriction and reduced size of the pulmonary vascular bed. In severe instances, this may result in an increase in pulmonary arterial pressure and, in turn, an increase in right ventricular work to maintain pulmonary blood flow. When the work requirements of the right ventricle exceed its capacity, right ventricular failure occurs, leading to a decrease in cardiac output followed by a decrease in systemic blood pressure and the development of shock (Norris, 2019). Clinical Manifestations Symptoms of PE depend on the size of the thrombus and the area of the pulmonary artery occluded by the thrombus; they may be nonspecific. Dyspnea is the most frequent symptom; the duration and intensity of the dyspnea depend on the extent of embolization. Chest pain is common and is usually sudden and pleuritic in origin; however, it may be substernal and may mimic angina (Thompson & Kabrhel, 2020). Other symptoms include anxiety, fever, tachycardia, apprehension, cough, diaphoresis, hemoptysis, and syncope. The most frequent sign is tachypnea (rapid respiratory rate) (De Palo, 2020). In many instances, PE causes few signs and symptoms, whereas in other instances, it mimics various other cardiopulmonary disorders (e.g., pneumonia, heart failure). Obstruction of the pulmonary artery can result in pronounced dyspnea, sudden substernal pain, rapid and weak pulse, shock, syncope, and sudden death (Thompson & Kabrhel, 2020). Assessment and Diagnostic Findings Because the symptoms of PE can vary from few to severe, a diagnostic workup is performed to rule out other diseases. The initial diagnostic workup may include chest xray, ECG, pulse oximetry, arterial blood gas analysis, D-dimer assay and MDCTA or pulmonary arteriogram or V./Q. scan. The chest x-ray is usually normal but may show infiltrates, atelectasis, elevation of the diaphragm on the affected side, or a pleural effusion. The chest x-ray is most helpful in excluding other possible causes. In addition to sinus tachycardia, the most frequent ECG abnormality is nonspecific ST-T wave https://herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zSNYYvz6N%2bxRwegtqPK%2fJ7UsPJxuq7nE1D4sTAvq22Nk5Sl… 2/3 2/22/24, 2:02 PM Realizeit for Student abnormalities. If an arterial blood gas analysis is performed, it may show hypoxemia and hypocapnia (from tachypnea); however, arterial blood gas measurements may be normal even in the presence of PE (De Palo, 2020). MDCTA is the criterion standard for diagnosing PE. The MDCTA can be performed quickly and provides the advantage of high-quality visualization of the lung parenchyma (Weinberger, Cockrill, & Mandel, 2019). If MDCTA is not available, pulmonary angiography is considered a reasonable alternative diagnostic method (Ouellette, 2019). The pulmonary angiogram allows for direct visualization under fluoroscopy of the arterial obstruction and accurate assessment of the perfusion deficit. A specially trained team must be available to perform the procedure, in which a catheter is threaded through the vena cava to the right side of the heart to inject dye, similar to a cardiac catheterization. The V./Q. scan continues to be used to diagnose PE, especially in facilities that do not use pulmonary angiography or do not have access to MDCTA. The V./Q. scan is minimally invasive and requires IV administration of a contrast agent. This scan evaluates different regions of the lung (upper, middle, lower) and allows comparisons of the percentage of V./Q. in each area. This test has a high sensitivity but is not as accurate as an MDCTA or pulmonary angiogram (De Palo, 2020). https://herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zSNYYvz6N%2bxRwegtqPK%2fJ7UsPJxuq7nE1D4sTAvq22Nk5Sl… 3/3