If a heavily blood stained effusion is noted, use an EDTA (purple top) blood container to measure the haematocrit of the fluid; if >50% of peripheral haematocrit, haemothorax is diagnosed.
Check coagulation profile.
In most cases this is probably due to tearing of pleural adhesions.
It may be due to malignancy, arterio-venous malformation, but also due to a leaking aortic aneurysm.
It may be a complication of a pleural aspiration or drain insertion.
Cases should be discussed with the Cardiothoracic Surgical Service in the first instance.
In most instances a large bore chest drain is required (>28 French).