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I've heard it said various times that the body's tissues will begin to necrotize after being cut off from the blood supply for only a few minutes, but that can't be true.

A few years ago, I woke up one morning and apparently I'd been sleeping just right so that the main artery to my left arm was totally pinched closed, because it was completely numb. Not just "arm's fallen asleep", either; I had no mental control over the entire arm and no feeling in it. I could lift it up with my right hand, and it would fall back down immediately when I let go of it, and I didn't feel anything when it landed on the mattress. It kind of freaked me out at first, but in just a few minutes I felt the "pins and needles" feeling of circulation returning, and it was 100% back to normal within less than an hour.

Given that I had presumably been sleeping on it like that for several hours, and yet I somehow didn't end up with a dead, useless arm that needed to be amputated, I know from personal experience that tissue doesn't die within a few minutes. So how long does it really take?

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    $\begingroup$ Your supposition is incorrect. A limb or other body part goes numb because a nerve is blocked, not because the blood supply is cut off. If you had truly completely cut off either the subclavian or brachial artery for that long, your arm would be deep purple. $\endgroup$ – MattDMo Oct 26 '15 at 21:51
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    $\begingroup$ It depends on the tissue type and on the circumstances. Brain cells start to die after 5 minutes, while heart cells die after 2 hours without oxygen. You can slow down the process by cooling down the body. $\endgroup$ – inf3rno Oct 27 '15 at 2:50
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    $\begingroup$ In medical school, we called this Saturday Night Palsy (or Honeymoon Palsy) - key emphasis on palsy - a nerve injury, not an arterial blockage. $\endgroup$ – anongoodnurse Oct 27 '15 at 10:55
  • $\begingroup$ @anongoodnurse "Saturday Night Palsy (or Honeymoon Palsy)" is that because it is generally alcohol that suppresses your CNS so that you do not move or change position in your sleep? Or does it have to do with someone else sleeping on your body part and it going numb from nerve compression? Serious question. $\endgroup$ – AMR Oct 28 '15 at 2:14
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    $\begingroup$ @AMR - Both, actually. Seriously. The inebriate falls asleep in a bad position and stays that way; the honeymooners snuggle, her head on his arm usually. $\endgroup$ – anongoodnurse Oct 28 '15 at 4:17
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As EMT (Emergency Medical Technician) instructors will tell you now, when wearing a tourniquet, you have about four hours to get the injury to a vascular surgeon and get it cared for appropriately. The rule therefore is four hours. However, the common thread I see in most sources is that about an hour and a half is the longest you want to go without blood flow to a limb.

As far as what happened to you, it sounds more like the limb simply fell asleep. When a limb falls asleep, it is getting the nerve pinched off for a time as well as loosing some blood flow. However, this is not a complete loss and so your arm is able to survive because it is still receiving enough oxygen and other nutrients to sustain its existence (as well as having toxins and CO2 pumped away from it).

I had a very difficult time finding any concrete, scientific information on this subject overall.

So, if you would like more information about this, please visit the following links. The first is a WikiPedia link on Limb Infarctions (or an embolism in a limb). The second is from Mental Floss on Why Limbs Fall Asleep. The third is a somewhat random article on someone's personal experience on Sleeping on their arm.

So, in summary: although I could find no solid evidence on how long a limb can live without its blood supply, it appears to be about 2-4 hours (some sources say 5-8); however, I would like to add that your case appears to be a severe case of an asleep limb, you were/are likely in no danger. Also, if your arm indeed did have circulation completely cut off, it would have turned pale, then blue and later a livid red and purple as the blood began to pool; you then would begin to experience the effects of the limb dying i.e. necrosis, gangrene.

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  • $\begingroup$ The Mental Floss article says that it involves circulation being cut off as well as the nerve being pinched. $\endgroup$ – Mason Wheeler Oct 26 '15 at 23:10
  • $\begingroup$ @MasonWheeler Oh dear... Thanks for pointing that out, I shall change that when I get the opportunity. $\endgroup$ – L.B. Oct 26 '15 at 23:30

protected by Chris Jan 21 '17 at 15:11

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