[Volumetry of pleural effusion in multi-morbidity, postoperative patients of a surgical intensive care unit. Comparison of ultrasound diagnosis and thoracic bedside image].

Aim of this study was to evaluate the importance of chest ultrasound and chest x-ray for the indication of thoracic drainage of pleural effusions in patients of an operative intensive care unit. Between December 1996 and June 1997 21 patients were included in a prospective trial in the operative intensive care unit. 26 thoracic drainages were used to drain pleural effusions. In all patients chest radiography in supine position and chest ultrasound were performed to assess the need of pleural drainage. Pleural fluid measured radiologically was categorized into 3 groups: pleural fluid less than 500 ml, 500 to 1,000 ml or more than 1,000 ml. The amount of the pleural effusion was sonographically determined by a standardized formula. After complete drainage of the pleural space the real volume of the fluid was measured and compared with the estimated value. The real amount of the fluid was correctly determined by chest radiographs in 16 cases (62%) and by chest ultrasound in 18 patients (69%). Pleural effusions less than 600 ml sonographically correlated much better with the real amount of the fluid than pleural effusions above 600 ml. In 8 cases (31%) ultrasound provided an additional information for correct indication of drainage. Considering both x-ray of the chest in supine position and chest ultrasound the correct indication to drain the pleural effusion was achieved in 25 cases (96%). In this prospective trial we compared chest ultrasound and chest radiography and demonstrated that ultrasound is more suitable to determine the amount of pleural effusions than radiography. In case of clinical and radiological suspicion on pleural effusion demanding for drainage a chest ultrasound should be performed to avoid underestimation of pleural fluid.