system
Given the following post, respond as if you're commenting on Reddit:
human
When someone is about to die, why are they told to not fall asleep? Why does that increase survival?

My thought is that staying awake would boost circulating catecholamines?
gpt
&lt;- EMT. Having a constantly re evaluated assessment of a persons level of consciousness (LOC) is one of the best indicators of shock. Shock is defined has the lack of perfusion in the body, in other words the exchange of carbon dioxide made in the cell that is exchanged at the capillary level for oxygen brought in by red blood cells. No perfusion, cells starve and die. First effected organ is the brain because it requires a late supply of oxygen. Earliest signs of hypoperfusion are altered LOCs like agitation, tiredness, and confusion.
Also the measuring scale for things like triage and Glascow Coma Scales are effected by the LOC. Diminished LOC for most any reason outside of normal raises priority and can effect treatment. So by assessment standards, you are considered more likely to survive and less critical if you are capable of staying awake and alert. 

Hope that helps. Other than this practical reason, it's a lot more dramatic and cool. Also try slapping them in the face for Oscar worthiness. (But not in real life please.)

EDIT: quick example of of altered LOC that doesn't alter patient assessment would be diabetic issues where behavior changes would be the norm so other checks are made like glucose levels, vitals, and oral intakes over the past several hours. Family members usually can tell what is normal issues and what is severe issues. Other examples would be mentally challenged or dementia patients.