My husband was in a serious car accident and the doctor said he has a "hemopericardium." what is that?

Blood around heart. The heart is surrounded by a sac. A hemopericardium is when blood is contained in that sac and surrounds the heart.
Blood around heart. The pericardium is a thin sac covering the heart. It is usually empty and just acts as a skin. It can fill with fluid-effusion- or blood. This is diagnosed with echocardiogram. If the sac fills too much, the heart cannot fill with blood and thus cannot pump effectively. This is called tamponade, which is very dangerous and must be drained. The treatmment depends on the size and cause.