The medical apparatus has lines that are connected to the vascular system of a patient. To ensure that an accidental escape of blood is identified, a camera is provided and is directed at the extracorporeal blood circuit of the patient. The image signals from the camera are processed in the sense that the color of blood and/or its arrangement in the image area in the camera image is determined, wherein the size of the recorded image area with the color of blood is also evaluated. In this way, an extracorporeal blood loss can be detected and signaled automatically.
