I'm quite afflicted with a specific set of conditions I'm trying to figure out.

I'm trying to find a way (if there is one) that someone could be unconscious for roughly twelve hours under some conditions, maybe more, maybe less, but most preferably with the least amount of blood loss possible.

I'm looking for something along the lines of dehydration, hungry, physical exhaustion, perhaps even some mental. I would like for some blood loss, but not something severe, like a liter.

All of this, added on top of some four hours of a casual paced walk, let's go with 3.1 miles an hour, the average walking speed. Then, maybe six to eight hours of combined sprinting paces, a few rests, and some more walking. Again, on top of this, the environment is desert-like.

If something like this is not possible, then if anything, perhaps someone could help me set up a set of conditions that works with this, just something around the ten to twelve hour mark of unconsciousness.

I've read that long periods of being fainted can be serious signs of fatal injury, but I'm not entirely sure. I've looked for a solid answer to my particular question, but haven't been conclusive. It is worth mentioning that I have no experience in any field of biology, study of how the body works, etc.

By that, any information pertaining to this topic I would be severely thankful for.

  • 3
    $\begingroup$ I have done this, at least as far as up to the part about walking. Alcohol and Desert (or other) sunlight do not mix well, particularly in large quantities. I lived, obviously, but was 'out' for 13 hours. Later, I found that death might have been an upgrade. $\endgroup$ – Joe May 24 '17 at 21:18
  • $\begingroup$ @Joe Must have been a Apocalypse-Class hangover $\endgroup$ – Joe Kissling May 24 '17 at 21:23
  • $\begingroup$ Given the chance, I'd probably render myself unconscious for about 12 hours after a hard day of exercise in the desert. Sleep is a wonderful thing. $\endgroup$ – ckersch May 24 '17 at 22:38
  • 1
    $\begingroup$ A tricky question. As you alluded to, the class of things that can knock you out for half a day is similar to the class of things that you will not wake up from on your own (and ultimately prove fatal without medical intervention). Do you want your character to spontaneously awaken after 10-12 hours? Or will something wake him up? If so, what kind of stimulus? Obviously someone yelling your name and digging their knuckles into your sternum (common in first aid) is going to wake you up from more things than, say, a light breeze. $\endgroup$ – type_outcast May 25 '17 at 1:07

Alright, so let's break this down. In our environment, we have the following elements definitely afflicting the individual:

  • Exposure to desert conditions
  • Hunger
  • Fatigue
  • Dehydration
  • Blood loss (For the record, a liter of blood loss could be considered severe. It's not enough to induce hypovolemic shock, but it is enough to cause a slew of problems like weariness and dizziness and poor coordination.)

What we want is to find an appropriate mix of these elements (along with some other potential elements) that will cause this person to become unconscious for an extended period of time -- say, 12 hours. In other words, we're putting this person in a coma.

These sorts of things tend to cause bouts of brief unconsciousness, but not a state of comatose, unless anything is particularly severe. The type of extended unconsciousness that I believe you're looking for can only be achieved through some sort of injury done to the brain. Even with normal unconsciousness, what's really happening is a malfunction in the brain's neuron system.

If we break this down, there are three main ingredients that we want to look at: Dehydration, blood loss, and physical exhaustion. Desert conditions lead to dehydration which is the primary concern, and hunger in the short-term only serves to hasten fatigue and doesn't pose a major threat to an individual.


Most living beings are majority water, and need a regular intake of it in order to survive. Of the three listed conditions, this one is the most life threatening when taken in isolation. For mammals, water carries important nutrients throughout the body, and helps regulate internal temperature.

Dehydration alone doesn't cause comas, though, until it becomes severe. Before you experience extended unconsciousness, you will experience fatigue, delirium, hallucinations, nausea, muscle spasms, and organ failure. If you want to go through the dehydration route, then you're introducing a lot of risk. Once someone falls into a coma from dehydration, they are at serious risk of death. Since this person is in a desert, this is a potential route you can take, but it's also a very risky one.

Blood Loss

The loss of a liter of blood in humans equates to a class II hemorrhage. The symptoms of blood loss at this level are surprisingly similar to the symptoms of moderate dehydration: lower blood pressure, dizziness, cold skin temperature due to vasoconstriction, accelerated heart rate. However, no unconsciousness. If you want to knock someone unconscious purely from blood loss, you have to venture into the territory of life-threatening injuries.

Physical Exhaustion

This is the route you probably want to take, but it's not a perfect mold of what you're after. Push someone in the desert, force them to do periods of physical exercise for several hours on end without any food or water, and injure them a bit. They may slip into unconsciousness every now and again if their body simply can't handle the exertion, and they'll be deficient on several layers of coordination, but they won't be totally unresponsive.

This sort of stress can cause memory loss and poor capacity for movement. This is probably as close to what you want as you're going to get.

Note that I'm not a medical professional, nor am I a biologist. I believe most of what I said is accurate, but if you want to be concrete with the accuracy of your worldbuilding, you may want to refer to other sources.

  • 2
    $\begingroup$ The best non-fatal way to combine these things with a prolonged unconsciousness is to hit the hero in the head. He collapses under exhaustion, hits himself on the head, he's nocked out momentarily, but then sleeps for more than 10 hours. It also explains blood loss. :) $\endgroup$ – Rekesoft May 25 '17 at 7:50
  • $\begingroup$ I think you should take the blood loss pick. I think its the perfect one, you can like make the character have a big wound but thats it, he for example could stop the bleeding using pressure (for example a belt) and he passes out due to blood lost, while the 12 hours go by, he has alreaddy produced enough blood to recover a little. Id go that way, the other ones seems too risky since he is in a desert so no acess to water and resting with intense heat is hard $\endgroup$ – jeyejow May 25 '17 at 15:29

Well, I regularly sleep twelve hours when I've been sleep-deprived for a few days and then don't have to get up the next morning (i.e. on a weekend). So if your unconscious person has only gotten a few hours of sleep per night over the last few days, and then finally got a chance to rest freely, they could easily be out well into the afternoon, if they went to sleep early in the morning.

In order for someone to be sufficiently sleep-deprived for this to work, something will need to wake them up a few hours after they go to bed for several days in a row. My alarm clock has done a pretty good job of that in my personal experience; if that doesn't work in your setting, maybe your dude is being chased by some very noisy bad guys?

You ask about how exhaustion, dehydration, hunger, and blood loss might affect this situation. I'll be honest; I don't know. That's well outside my area of expertise. However, I'd imagine that any of those factors would only decrease the amount of sleep deprivation needed for it to happen.


12 hours is nothing, I've often done more than that after a couple of nights with no sleep. So sleep deprive your hero and he will eventually collapse on his own and sleep through a heavy metal concert without waking.

Unsure about others but after a couple of nights of no sleep I start hallucinating and if I let myself relax and sleep nothing has managed to wake me within 12 hours except vigorous physical shaking.

  • $\begingroup$ i really like that idea! $\endgroup$ – jeyejow May 25 '17 at 15:30

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.