Hello- My Father In Law Passed Out The Other Day

Hello- my father in law passed out the other day and banged his head in the bathroom. He is approx 73 years old, and he had diareah for several days before he passed out. He had major indigestion after Thanksgiving- he things it is b/c he overate - and then he had a bad stomach. Do you think he blacked out b/c of dehydration from having an upset stomach for days after overeating on Thanksgiving?