What physiological change can result from treating a casualty with too much fluid?

Treating a casualty with excessive fluid can lead to worsened internal bleeding due to a phenomenon known as volume overload. This occurs when too much fluid increases the blood volume, potentially raising blood pressure and disrupting the body's ability to manage bleeding effectively. High blood pressure can cause fragile blood vessels at the site of injury to rupture further, aggravating internal bleeding.

Additionally, excessive fluid can dilute clotting factors in the blood, compromising the body’s natural hemostatic processes. Thus, while fluid resuscitation is vital for a patient with hemorrhagic shock, it's crucial to monitor the volume carefully to avoid exacerbating internal bleeding and other complications.