Pleural effusion is an abnormal amount of pleural fluid in the pleural space. Pleural effusions accompany conditions with increased capillary permeability, increased hydrostatic pressure, decreased oncotic pressure, increased negative intrapleural pressure, or decreased lymphatic drainage. Pleural effusion affects 1.3 million individuals in the United States each year (Light, 2007).
The pleura are thin membranes covering and extending completely around the lungs to the hilar root. The parietal pleura cover the chest wall, diaphragm, and mediastinum. They are in close proximity to microvessels and lymphatics that contribute to production and reabsorption of pleural fluid. The visceral pleura cover the lungs and intralobular fissures. The pleural space is a potential space between the visceral pleura and the parietal pleura filled with 7 to 20 ml of pleural fluid that acts as a lubricant. Pleural fluid originates from the systemic vessels in the pleural membrane. In a healthy individual, the rate of absorption equals that of formation, 0.01 ml/kg/hr. The rate of absorption can increase 10- to 20-fold to keep up with an increased rate of formation (Light, 2007). Reabsorption is thought to occur passively through the lymphatic system.
Accumulation of greater than 150 ml of pleural fluid will cause a patient to experience symptoms such as dyspnea with activity and at rest, a dry cough, chest discomfort, and fatigue.
Decreased ability of fluid to exit the pleural space can be due to endocrine abnormalities, injury to tissue from radiation or medications, or infiltration of the lymphatics or pleural capillaries by tumor. External factors that contribute to decreased exit of fluid from the pleural space include limitation of respiratory motion due to pain from surgery, extrinsic compression of lymphatics from granulomas, pleural fibrosis, or decreased intropleural pressures that are present with “trapped lung.”
Classification of Pleural Effusions
Pleural effusions can be classified as transudative or exudative. Transudate is fluid accumulation due to imbalances in hydrostatic and oncotic pressures in the chest. A transudate can result from movement of fluid from the peritoneal or retroperitoneal space. Patients with congestive heart failure, nephrotic syndrome, hypoalbuminemia, liver disease, atelectasis, or lymphatic obstruction have transudative effusions.
Exudative pleural effusions are pathologic processes that increase permeability of the pleural surface to protein or decrease lymphatic flow. Disease in a variety of organ systems can lead to exudative effusions. Mechanisms can include infections, malignancy, immunologic responses, lymphatic abnormalities, noninfectious inflammation, and movement of fluid from below the diaphragm. Malignant pleural effusions can be due to pleural metastasis, mediastinal node involvement, chylothorax, bronchial obstruction, or pericardial involvement.
Diagnosing Pleural Effusions
Chest x-rays identify the presence of pleural effusions when more than 500 ml of fluid is present. Blunting of the costraphrenic angles is seen. Lateral decubiti films may assist in estimating the amount of fluid present. Computed tomography of the chest is more sensitive in identifying the extent and location of effusion and pleural thickening.
A thoracentesis can be performed on an outpatient basis or at the bedside to diagnose a pleural effusion. No more than 1.5 L of fluid and cells should be removed for culture and cytology to prevent rebound accumulation of fluid and reexpansion pulmonary edema (Feller-Kopman, Berkowitz, Boiselle, & Ernst, 2007). Thoracentesis is contraindicated in patients who are anticoagulated, have small loculated effusions, or have an area of infected skin at the site to be used for needle insertion. Possible complications of thoracentesis include pneumothorax, hemothorax, intraabdominal injury, and pulmonary edema.
Pleural Fluid Analysis
Analysis of pleural fluid to assist in identifying the underlying cause of the effusion includes observation of the color. Yellow fluid indicates a transudate; red or bloody fluid a malignancy; milky white fluid a chylothorax; and dark green fluid a biliothorax. Color may reveal tube feeding or central venous catheter infusate as an iatrogenic cause of a pleural effusion. Pus-like odorous fluid may indicate infection. Viscous fluid would suggest mesothelioma. Other pleural fluid tests that aid in determining the underlying cause of the effusion include cytology, protein ratios, lactate dehydrogenase, cholesterol, glucose, pH, triglycerides, cell counts, eosinophils, and hematocrit (Porcel & Vives, 2003).
Providing supplemental oxygen and managing anxiety, pain, and activity tolerance in patients with pleural effusions is important. Educating the patient, the family, and care providers about interventions to address these symptoms is beneficial (Wing, 2004).
Management of Pleural Effusions
Pleural effusions are managed by treating the underlying disease process. For example, if a patient had a history of congestive heart failure, adjustments to medical management of the condition to attempt relief would be tried first.
Patients may undergo repeat thoracentesis to relieve dyspnea.
Insertion of a large bore chest tube for drainage may be considered, allowing for greater flow rate of fluid when connected to a drainage device. This option requires patients to be hospitalized for prolonged periods, is costly, is painful, and limits patients’ activity. In some cases, the drainage of pleural fluid does not decrease.
Pleurodesis may be attempted. Instillation of a chemical agent such as talc, doxycycline, or bleomycin into a chest drain causes a fibrotic reaction with the inflammatory response of the pleura. The reaction promotes fusing of the visceral and parietal pleura, eliminating the potential space where fluid can accumulate. Patients may experience pain or develop a talc-related fever secondary to the inflammatory reaction (Tan, Sedrakyan, Browne, Swift, & Treasure, 2006).
Placement of a long-term pleural catheter, such as the Plerux™ catheter, may be an option for patients with a chronic pleural effusion (Warren, Kalimi, Khodadadian, & Kim, 2008). The catheter can be accessed and fluid drained using a vacuum container, by the patient or a caregiver on a schedule or as the patient becomes symptomatic in the home setting.
Spontaneous pleurodesis may be achieved by keeping the pleural space dry. Patients may experience discomfort with draining and should consider pre-medication. Patients are instructed to drain no more than 1 L per 24 hours, but may drain more fluid if instructed by a physician.
Catheter removal is considered if the amount of fluid being drained decreases and the patient is asymptomatic. Patients may attempt draining and find they can drain no fluid. If they continue to experience symptoms, the catheter may be plugged or fluid may have accumulated in the opposite pleural space or a loculated area where the catheter is not placed. Decisions about catheter removal or replacement would need to be made.
Pleurectomy and decortication, stripping of the pleural membranes from the chest wall and lungs, may be performed at the time of a diagnostic thoracotomy or attempted when there is a trapped lung and pleurodesis cannot be performed. Decortication is a major thoracic operation that debilitated patients may not tolerate (Doelken, 2008). Coexisting conditions that contribute to symptoms must be treated before a surgical approach is considered.
Pleuroperitoneal shunts have been placed in an attempt to move fluid from the pleural space to the peritoneum for reabsorption with varying success.
Malignant pleural effusions or effusions caused by stage III or IV congestive heart failure may or may not resolve with the therapies described. Sometimes, a decision is made not to treat the effusion but instead to manage the symptoms with palliative care modalities. Comfort care may be the best option if life expectancy is only a few days. Use of systemic morphine as well as morphine inhalers may be beneficial for dyspnea.
Pleural effusions are a complication of a disease process in many physiologic systems. Management to maximize patient independence and relieve symptoms is the goal of care. A variety of treatment options are available. Patients’ overall physiologic status will direct treatment.
Mary Ellen Cordes, MS, RN, APRN-BC
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