A massive hemothorax is defined as a rapid accumulation of greater than 11.5 L of blood in the thoracic cavity. It is usually caused by rib fractures (intercostal or internal mammary vessel bleeding), lung injury, great vessel injury, cardiac injury, or diaphragmatic injury. The signs and symptoms of hemothorax include diminished breath sounds on the affected side, hypoxemia, hypotension, mediastinal shift, and respiratory distress.