Clinically Significant Pleural Effusion in Intensive Care: A Prospective Multicenter Cohort Study

Lung ultrasound and supine chest X-ray use in modern adult intensive care: mapping 30 years of advancement (1993-2023)

In critically ill patients with acute respiratory failure, thoracic images are essential for evaluating the nature, extent and progression of the disease, and for clinical management decisions. For this purpose, computed tomography (CT) is the gold standard. However, transporting patients to the radiology suite and exposure to ionized radiation limit its use. Furthermore, a CT scan is a static diagnostic exam for the thorax, not allowing, for example, appreciation of "lung sliding". Its use is also unsuitable when it is necessary to adapt or decide to modify mechanical ventilation parameters at the bedside in real-time. Therefore, chest X-ray and lung ultrasound are today's contenders for shared second place on the podium to acquire a thoracic image, with their specific strengths and limitations. Finally, electrical impedance tomography (EIT) could soon have a role, however, its assessment is outside the scope of this review. Thus, we aim to carry out the following points: (1) analyze the advancement in knowledge of lung ultrasound use and the related main protocols adopted in intensive care units (ICUs) over the latest 30 years, reporting the principal publications along the way, (2) discuss how and when lung ultrasound should be used in a modern ICU and (3) illustrate the possible future development of LUS.

Pleural effusion and thoracentesis in ICU patients: A longitudinal observational cross-sectional study

BACKGROUND

Pleural effusion is common among patients in the intensive care unit (ICU) but reported prevalence varies. Thoracentesis may improve respiratory status, however, indications for this are unclear. We aimed to explore prevalence, development, and progression of pleural effusion, and the incidence and effects of thoracentesis in adult ICU patients.

METHODS

This is a prospective observational study utilizing repeated daily ultrasonographic assessments of pleurae bilaterally, conducted in all adult patients admitted to the four ICUs of a Danish university hospital throughout a 14-day period. The primary outcome was the proportion of patients with ultrasonographically significant pleural effusion (separation between parietal and visceral pleurae >20 mm) in either pleural cavity on any ICU day. Secondary outcomes included the proportion of patients with ultrasonographically significant pleural effusion receiving thoracentesis in ICU, and the progression of pleural effusion without drainage, among others. The protocol was published before study initiation.

RESULTS

In total, 81 patients were included of which 25 (31%) had or developed ultrasonographically significant pleural effusion. Thoracentesis was performed in 10 of these 25 patients (40%). Patients with ultrasonographically significant pleural effusion, which was not drained, had an overall decrease in estimated pleural effusion volume on subsequent days.

CONCLUSION

Pleural effusion was common in the ICU, but less than half of all patients with ultrasonographically significant pleural effusion underwent thoracentesis. Progression of pleural effusion without thoracentesis showed reduced volumes on subsequent days.

Pleural effusion in critically ill patients and intensive care setting

Pleural effusion usually causes a diagnostic dilemma with a long list of differential diagnoses. Many studies found a high prevalence of pleural effusions in critically ill and mechanically ventilated patients, with a wide range of variable prevalence rates of up to 50%-60% in some studies. This review emphasizes the importance of pleural effusion diagnosis and management in patients admitted to the intensive care unit (ICU). The original disease that caused pleural effusion can be the exact cause of ICU admission. There is an impairment in the pleural fluid turnover and cycling in critically ill and mechanically ventilated patients. There are also many difficulties in diagnosing pleural effusion in the ICU, including clinical, radiological, and even laboratory difficulties. These difficulties are due to unusual presentation, inability to undergo some diagnostic procedures, and heterogenous results of some of the performed tests. Pleural effusion can affect the patient’s outcome and prognosis due to the hemodynamics and lung mechanics changes in these patients, who usually have frequent comorbidities. Similarly, pleural effusion drainage can modify the ICU-admitted patient’s outcome. Finally, pleural effusion analysis can change the original diagnosis in some cases and redirect the management toward a different way.

Risk Factors for Mortality Among Mechanically Ventilated Patients Requiring Pleural Drainage

Purpose

Pleural effusions are common in mechanically ventilated patients. However, the risk factors for poor outcomes after pleural drainage are poorly understood. This study aimed to identify factors that were associated with in-hospital mortality among mechanically ventilated patients who underwent pleural drainage.

Methods

This retrospective study evaluated 82 consecutive patients who required chest tubes during mechanical ventilation at two university-affiliated hospitals in Korea between January 2015 and June 2020.

Results

The median age was 76 years (interquartile range [IQR]: 64–84 years), and the median SOFA score was 11 (IQR: 7–13). Intensive care unit admission was most commonly because of pneumonia (n = 44, 53.7%) and 60 patients (77.9%) had exudative pleural effusions. During pleural drainage, the PaO₂/FiO₂ was 210 (IQR: 153–253); 45 patients (54.9%) were receiving vasopressors, and 31 patients (37.8%) were receiving continuous renal replacement therapy (CRRT). The multivariable regression analysis revealed that poor overall survival was independently associated with receiving vasopressors (adjusted hazard ratio [aHR]: 3.81, 95% confidence interval [CI]: 1.65–8.81, p = 0.002) and receiving CRRT (aHR: 5.48, 95% CI: 2.29–13.12, p < 0.001). The PaO₂/FiO₂ ratio was relatively stable through the third day of pleural drainage among survivors but decreased among non-survivors. The vasopressor dose decreased among survivors but remained relatively stable among non-survivors.

Conclusion

Among mechanically ventilated patients who required pleural drainage, use of vasopressors and CRRT was significantly associated with in-hospital mortality. On the third day of pleural drainage, the changes in PaO₂/FiO₂ and vasopressor dose were associated with in-hospital mortality.

Pleural Effusions in the Critically Ill and "At-Bleeding-Risk" Population

Thoracentesis is a common bedside procedure, which has a low risk of complications when performed with thoracic ultrasound and by experienced operators. In critically ill or mechanically ventilated patients, or in patients with bleeding risks due to medications or other coagulopathies, the complication rate remains low. Drainage of pleural effusion in the intensive care unit has diagnostic and therapeutic utility, and perceived bleeding risks should be one part of an individualized and comprehensive risk-benefit analysis.

Small Drainage Volumes of Pleural Effusions Are Associated with Complications in Critically Ill Patients: A Retrospective Analysis

Pleural effusions are a common finding in critically ill patients and small bore chest drains (SBCD) are proven to be efficient for pleural drainage. The data on the potential benefits and risks of drainage remains controversial. We aimed to determine the cut-off volume for complications, to investigate the impact of pleural drainage and drained volume on clinically relevant outcomes. Medical records of all critically ill patients undergoing insertion of SBCD were retrospectively examined. We screened 13,003 chest radiographs and included 396 SBCD cases in the final analysis. SBCD drained on average 900 mL, with less amount in patients with complications (p = 0.003). A drainage volume of 975 mL in 24 h represented the optimal threshold for complications. Pneumothorax was the most frequent complication (4.5%), followed by bleeding (0.8%). Female and lighter-weighted patients experienced a higher risk for any complication. We observed an improvement in the arterial partial pressure of oxygen and respiratory quotient (p < 0.001). We conclude that the small drainage volumes are associated with complications in critically ill patients—the more you drain, the safer the procedure gets. The use of SBCD is a safe and efficient procedure, further investigations regarding the higher rate of complications in female and lighter-weighted patients are desirable.