Study objectives: To assess the necessity of thoracentesis in febrile medical ICU (MICU) patients, and to evaluate the efficiency and reliability of sonographic effusion patterns for diagnosing empyema.
Design and setting: A prospective, 1-year, tertiary-care hospital study of febrile MICU patients with physical, radiographic, and ultrasonographic evidence of pleural effusion.
Patients: During this study period, we screened 1,640 patients who had been admitted to the MICU; of these, 94 patients had a temperature > 38°C for > 8 h with evidence of pleural effusion proven by chest radiography and ultrasound.
Intervention: Routine thoracentesis and pleural effusion cultures were performed in 94 febrile patients under portable chest ultrasound guidance. Three days later, if the first pleural effusion culture was inconclusive and the patient still had persistent fever of > 38°C, we repeated the diagnostic thoracentesis and pleural effusion culture. In total, 118 procedures were performed in those 94 febrile patients.
Measurements and results: In all, 58 patients (62%) had infectious exudates (parapneumonic, n = 36; empyema, n = 15; urosepsis, n = 3; liver abscess, n = 2; deep neck infection, n = 1; and wound infection, n = 1), 28 patients (30%) had transudates, and 8 patients (8%) had noninfectious exudates. The prevalence of empyema in febrile patients admitted to the MICU was 16% (15 of 94 patients). Analyses of the sonographic patterns of the 15 patients with empyema out of the 118 thoracenteses performed showed the following: anechoic pattern, 0% (0 of 47 procedures); complex nonseptated and relatively nonhyperechoic pattern, 0% (0 of 36 procedures); complex nonseptated and relatively hyperechoic pattern, 100% (2 of 2 procedures); complex septated pattern, 35% (11 of 31 procedures); and homogenously echogenic pattern, 100% (2 of 2 procedures). Hemothorax was the only complication, and it occurred in two patients (2%). Both patients had a favorable outcome after drainage.
Conclusion: Portable chest ultrasound examination and ultrasound-guided thoracentesis in febrile MICU patients are safe, feasible, and useful methods for diagnosing thoracic empyema. Our results suggest that only some sonographic patterns of pleural effusion (homogenously echogenic, complex nonseptated and relatively hyperechoic, and complex septated) deserve aggressive assessment and rapid management.