Pleural Disorders in the ICU: Causes, Symptoms, Diagnosis & Critical Care Management
Pleural Disorders in the Intensive Care Unit:
In some instances, pleural processes may be the primary cause of patients' critical illness; in most cases, pleural disorders are recognized as secondary processes related to patients' underlying illness.
Pleural Effusions
The pleural space is a potential space between the visceral pleura, which covers the outer surface of the lung, and the parietal pleura, which lines the inside of the chest wall. In this space, there is a small amount of fluid present that functions to mechanically couple the lung to the chest wall and lubricate the interface of the visceral and parietal pleura. Pleural fluid normally results from the filtration of blood through high-pressure systemic blood vessels and is drained from the pleural space through lymphatic openings in the parietal pleura that drain into parietal lymphatic vessels. In different disease states, fluid may originate from the interstitial spaces of the lungs, the intrathoracic lymphatics, the intrathoracic blood vessels, or the peritoneal cavity.
A pleural effusion is defined as an abnormal collection of fluid in the pleural space. Effusions occur when the rate of fluid formation exceeds the rate of fluid absorption.
Outlines the common causes of pleural effusions:
Congestive Heart Failure (CHF) accounts for 36%.
Pneumonia accounts for 22%.
Malignancy accounts for 14%.
Pulmonary Embolism accounts for 11%.
Other infections account for 7%, and remaining causes make up 10%.
Effusions are commonly classified as either exudative or transudative. An exudative pleural effusion implies a disease process directly affecting the pleura, causing it or its vasculature to be damaged. Examples include malignancy, pneumonia, PE, subdiaphragmatic abscess, or autoimmune diseases like lupus and rheumatoid arthritis. A transudative effusion results when the pleura itself is healthy but a disease process affects hydrostatic or oncotic factors (e.g., CHF, myxedema, or cirrhosis).
Clinical Manifestations and Diagnosis
Nonspecific signs and symptoms include chest pain (particularly when sharp and made worse by breathing) and dyspnea. Physical examination findings may include:
Dullness to percussion over the effusion.
Loss of fremitus.
Decreased breath sounds.
Crackles/egophony immediately above the effusion.
Asymmetric diaphragmatic excursion with inspiration.
Radiographically, the majority of ICU patients have effusions detected via portable X-ray. Findings include blunting of the costophrenic angle and a meniscus sign. On a lateral decubitus chest X-ray, if the fluid layers out at a distance greater than 1 cm, the amount of fluid is considered significant and often requires thoracentesis.
Evaluation and Management
1. Evaluation of the Unknown Effusion
When a pleural effusion is identified, the first step is to determine if a pulmonary embolism (PE) is suspected. If PE is suspected, a PE Protocol CT should be performed. If positive, the PE is treated; if negative, the clinician moves to assessing if the patient meets indications for thoracentesis. If PE is not suspected, the clinician evaluates if the patient meets criteria or has CHF. If the patient has CHF, they should be observed. If the patient does not have CHF but criteria, a lateral decubitus X-ray is obtained. If the fluid layers at a thickness greater than 1 cm, thoracentesis is performed; otherwise, the patient is observed.
2. Fluid Analysis and Management After Thoracentesis
Following thoracentesis, the clinician first evaluates the appearance of the fluid. If the fluid is purulent, the diagnosis is empyema, and a chest tube is required. If the fluid is bloody, the hematocrit of the fluid is compared to peripheral blood. If the fluid hematocrit is >50% of the peripheral blood, the diagnosis is hemothorax, requiring a chest tube.
For other fluid types, analysis is performed using Light’s or Heffner’s Criteria. If the fluid is a transudate, the patient is observed. If it is an exudate, the clinician checks for the presence of CHF or cirrhosis. If these are present, the Serum-Pleural Albumin Gradient is measured. If the gradient is >1.2, the fluid is treated as a transudate (observe); if ≤1.2, it is treated as an exudate and further diagnostic tests are pursued.
3. Parapneumonic Effusions
If a parapneumonic effusion is present and measures >1 cm on lateral decubitus X-ray, thoracentesis is performed. If the fluid meets criteria (loculation, pH <7.2, glucose <60, or pus), antibiotics and tube thoracostomy (chest tube) are initiated. If there is improvement, the tube is removed once signs of infection resolve and drainage is <150 mL/day. If there is no improvement, the clinician should consider fibrinolytics, thoracoscopy, or thoracotomy. If criteria are not met, the patient is treated with antibiotics and potentially serial thoracentesis.
4. Recurrent Malignant Effusions
Once a malignant effusion is identified via thoracentesis, the clinician assesses if symptoms improved. If symptoms improved but the fluid recurs in less than 3 weeks, options like pleurodesis or a PleurX catheter should be discussed.If it does not recur within 3 weeks, follow clinically. If symptoms did not improve after the initial thoracentesis, the clinician must investigate other causes of shortness of breath (e.g., PE). If another cause is found, treat it; if no other cause is found, treat the dyspnea symptomatically (e.g., narcotics).
5. Management of Pneumothorax
If a pneumothorax is suspected and the patient is unstable or a tension pneumothorax is suspected, high-flow oxygen and immediate needle thoracostomy followed by a chest tube are required. If the patient is stable, a chest X-ray is used to confirm the diagnosis. If the pneumothorax occupies ≤15% of the hemithorax, the patient is observed. If it occupies >15%, a tube thoracostomy is performed.
Special Procedures and Conditions
Indications for Thoracentesis :
Thoracentesis is indicated for effusions of unknown etiology, fever in the setting of long-standing effusion, air-fluid levels in the pleural space, rapid change in effusion size, or concern for developing empyema.
Diagnostic Criteria :
According to Light’s Criteria, a fluid is exudative if:
Pleural fluid to serum protein ratio is >0.5.
Pleural fluid to serum LDH ratio is >0.6.
Pleural fluid LDH is >2/3 the upper limit of normal for serum LDH.
Heffner’s Criteria defines an exudate if pleural fluid protein is >2.9 g/dL or pleural fluid LDH is >0.45 the upper limit of normal.
Malignant Effusions:
The most common primary tumors causing malignant effusions are Lung (38%), Breast (17%), and Lymphoma (12%).
Hemothorax and Pneumothorax:
A hemothorax is defined by a pleural fluid to blood hematocrit ratio of >0.5. Causes can be traumatic, nontraumatic (metastatic disease), or iatrogenic (central line placement). A pneumothorax is the presence of air in the pleural space and can be a life-threatening emergency if a "one-way valve" process creates a tension pneumothorax.
Chest Tube Removal:
A chest tube can be removed when the pneumothorax has resolved, there is no air leak, and the lung remains expanded after the tube is placed on water seal for 24 hours.