Once, I fell asleep with my arm in a particular position, and when i got up, for at least 5 minutes, I had no sensation or control. I wonder, how much longer would it have taken?
In: Biology
About two hours, but it varies.
Two hours is the usual guideline maximum time for a tourniquet.
Serious damage *could* occur in 30 minutes, or even less – it depends on lots of things. Which limb, how big the person is, how fit they are, what the temperature is, what medication they’ve taken, etc.
The common guides for using tourniquets is that damage may occur after 15-30 minutes, but that after around 2 hours there may be too much damage in the limb. It depends on a lot of circumstances like temperature, blood loss, etc. And expect these numbers to change as the war in Ukraine is the first large scale war with wide spread tourniquet use and difficult medical evacuation strategies. So this is the first time we can actually study the effects of blood loss to a limb in large scales and get reliable trend data. There are already updated procedures being sent to the fighting troops trying to reduce the number of amputations.
What you are describing though is not comparable to using a tourniquet. The pain of losing blood flow in your limb is far too great to allow for any kind of sleep. What can happen is that you might lose capillary blood flow to a pressure area. So it is only around a certain spot that blood flow gets reduced, not the entire limb. This can eventually cause bed sores after hours in the same position. If there is a nerve cluster going through this pressure point then the nerves can stop working. So the limb does have plenty of blood going to it, but there is a breakdown in communication between your limb and your brain.
My eli5 question regarding the numbness of limb would actually be about what actually causes the numbness, loss of blood flow or some other obstruction to the nerves in the limb.
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