Chest radiograph appearances of hemothorax must be distinguished from pulmonary parenchymal opacities. With large hemothoraces, physical examination will reveal dullness to percussion and diminished or absent breath sounds. Chest radiography will often appear normal where clinical signs are confined to the base. This is due to the necessity of taking chest radiographs supine in many critical care situations. Where possible, erect radiographs should be taken. The presence of fluid is more obvious and a rough estimate of volume can also be made (Fig, 1). Volumes of 500 ml or more have been drained from patients whose initial supine films show no obvious intrapleural fluid. Lateral decubitus views can also raise the diagnostic accuracy. If air is present, the estimate may be more accurate as the upper border of the fluid is thrown into sharper relief. Routine radiology cannot distinguish blood from other pleural effusions, apart from chylothorax which has a high fat content.
Fig. 1 Approxiate volume of hemothorax on an erect chest radiograph in a patient of normal build: fills the costophrenic angle, 200-500 ml; air plus fluid level 5 cm over diaphragm, 1000 ml; separates the chest wall and diaphragm by 1 cm, 1500-2000 ml.
The diagnosis of hemothorax usually follows the identification of fluid on chest radiography. Changing the position of the patient will also determine whether the blood is free in the pleural space or is loculated. When available, CT scanning will help to identify the precise location of blood. Massive hemothorax is only diagnosed definitely when 2 liters drains from the chest.
The initial finding of a hemothorax in the non-traumatic patient is unexpected as other causes of intrapleural fluid are so much more common. Finding blood at pleural aspiration should not on its own be a cause of alarm. Blood removed from a probable hemothorax should be examined to assess whether clotting occurs in a bottle. The bloodstained fluid should be spun to establish its hematocrit, and bacteriology should be carried out to exclude infection. The blood pressure and pulse rate should be measured regularly.
If the patient is hemodynamically stable and not in respiratory failure, further radiological investigation should be undertaken if available. A CT scan with intravascular contrast enhancement may be carried out and the surgeons consulted. Magnetic resonance imaging may give some additional information, particularly in distinguishing blood from other pleural effusions, and where available it may be appropriate to carry this out before aspiration.
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