Its cause is usually traumatic, from a blunt or penetrating injury to the thorax, resulting in a rupture of the serous membrane either lining the thorax or covering the lungs. This rupture allows blood to spill into the pleural space, equalizing the pressures between it and the lungs. Blood loss may be massive in people with these conditions, as each side of the thorax can hold 30 to 40% of a person's blood volume. Even minor injury to the chest wall can lead to significant hemothorax.
If left untreated, the condition can progress to a point where the blood accumulation begins to put pressure on the mediastinum and the trachea, effectively limiting the amount that the heart's ventricles are able to fill. The condition can cause the trachea to deviate, or move, toward the unaffected side.
A hemothorax is managed by removing the source of bleeding and by draining the blood already in the thoracic cavity. Blood in the cavity can be removed by inserting a drain (chest tube) in a procedure called a tube thoracostomy. Usually the lung will expand and the bleeding will stop after a chest tube is inserted. The blood in the chest can thicken as the clotting cascade is activated when the blood leaves the blood vessels and is activated by the pleural surface, injured lung or chest wall, or contact with the chest tube. As the blood thickens, it can clot in the pleural space (leading to a retained hemothorax) or within the chest tube, leading to chest tube clogging or occlusion. Chest tube clogging or occlusion can lead to worse outcomes as it prevents adequate drainage of the pleural space, contributing to the problem of retained hemothorax. In this case, patients can be hypoxic, short of breath, or in some cases, the retained hemothorax can become infected (empyema). Therefore adequately functioning chest tubes are essential in the setting of a hemothorax treated with a chest tube. To attempt to minimize the potential for clogging, the surgeons will often place more than one tube, or large diameter tubes. Maintaining an adequately functioning chest tube is an active process, usually for the nurses, that often requires tapping the tubes, milking the tubes, or stripping the tubes to minimize potential for clogging in the tube in the setting of a hemothorax. When these efforts fail a new chest tube must be placed, or the patient must be taken to the operating room by a surgeon to open the chest and remove the blood clot, and re insert adequately functioning chest tubes.
Thrombolytic agents have been used to break up clot in tubes or when the clot becomes organized in the pleural space, however this is risky as it can lead to increased bleeding and the need for reoperation. Therefore, ideally, the tubes maintain their function so that the blood cannot clot in the chest or the tube.
In some cases bleeding continues and surgery is necessary to stop the source of bleeding. For example, if the cause is rupture of the aorta in high energy trauma, intervention by a thoracic surgeon is mandatory.