(OP) Obviously, we're talking about fiction, and plot rules all ;) but (non-drug-induced) unconsciousness is generally very brief.
For instance, the three most commonly used (in the US) scales for grading concussion all have three grades with III being the most severe. Two of those scales count any loss of consciousness at all as a Grade III concussion. The third counts loss of consciousness of under 5 minutes as Grade II and in excess of 5 minutes as Grade III. It takes moderate traumatic brain injury to cause unconsciousness of over half an hour, and an injury of that severity would almost certainly cause long term (possibly permanent) disability. Even mild TBI can cause permanent disability. Ten years out from my own mild TBI, I still have dysnomia and short term memory deficits.
Unconsciousness of multiple hours duration due to low blood pressure or blood loss would likely result in kidney and brain damage (and potentially other organ damage.
There are certainly other causes of unconsciousness (hypoglycemia, heat stroke, hypothermia, epilepsy, asphyxia), most of which carry even more complications.
Please don't think I'm trying to tell you what to write. Ignore anything that doesn't suit the story you want to tell. :)
Re: PSA: Wound care - Also can do some medical Q&A
For instance, the three most commonly used (in the US) scales for grading concussion all have three grades with III being the most severe. Two of those scales count any loss of consciousness at all as a Grade III concussion. The third counts loss of consciousness of under 5 minutes as Grade II and in excess of 5 minutes as Grade III. It takes moderate traumatic brain injury to cause unconsciousness of over half an hour, and an injury of that severity would almost certainly cause long term (possibly permanent) disability. Even mild TBI can cause permanent disability. Ten years out from my own mild TBI, I still have dysnomia and short term memory deficits.
Unconsciousness of multiple hours duration due to low blood pressure or blood loss would likely result in kidney and brain damage (and potentially other organ damage.
There are certainly other causes of unconsciousness (hypoglycemia, heat stroke, hypothermia, epilepsy, asphyxia), most of which carry even more complications.
Please don't think I'm trying to tell you what to write. Ignore anything that doesn't suit the story you want to tell. :)