Help please? how serious would a brain injury be, if the person has to stay in the critical care unit?

Normally moderate: To severe. Beyond that, it is difficult to say. Sometimes critical care units can just be observation, where other times patients can stay for extended amount of times, just depending on the brain injury itself. At the very least though, i would assume a moderate brain injury has occurred. Without more info, that is about the best i can offer with any accuracy. Best wishes for you during this time.

It depends: It really depends on the individual case. There are certain brain injuries that require ICU care to prevent and treat the injury as well as complications. There are also some brain injuries that require close monitoring in the ICU not specifically for aggressive treatment but more so to anticipate late events and intervene if required.