system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do patients who suffer severe trauma often complain of being thirsty?
gpt
Patients who have suffered a severe trauma resulting in a lot of blood loss begin to go into shock. Without enough blood to circulate the oxygen to all of their organs, muscles, etc, their body goes into a natural state of damage control. What blood supply you do have is sent to the brain/heart in an attempt to keep these 2 most vital organs running. However, with oxygen practically cut off to the rest of your body, things begin to shut down; and one of the first systems to be ignored for the "greater good" is your digestive system.   


Naturally, you will experience a water craving because (even though everything is going haywire) your body wants to get back to normal and replace your blood volume. However, drinking water will cause the patient to vomit (because the digestive system is offline) which will cause further imbalances in the body and the possibility of breathing in/choking on the vomit resulting in respiratory distress.