Waking Up and Losing Circulation

The other night I woke up in the middle of the night and my arm was a practically lifeless mass. I had slept on it in such a way as to cut off the circulation. I have done this before as I am sure others have. it took a while but eventually the arm returned back to normal, but I couldn’t help thinking that if I hadn’t woken up I would have permanently damaged my arm. Is there some sort of internal mechanism that makes sure we wake up before anything permanent can happen or is it just dumb luck?

I think the permanent mechanism that makes you wake up before gangrene sets in is called “waking up”. You’re safe as long as your arm hasn’t turned black during the night. :smiley:

On a related note, if I fall asleep on my back, my nose will fall asleep. Sometimes I can actually feel it start to tingle as I fall deeper into slumber. When I wake up, my nose starts to “wake up” and as the feeling comes back, I have a tremendous sneezing fit that lasts about 5 minutes. Needless to say, I try to sleep on my stomach. I do not know if this is normal, but so far, my nose has not turned black and fallen off.

::Typing fast::

The sensation of a limb falling asleep is not due to a lack of blood flow but instead due to compression of peripheral nerves. You can prove this to yourself by:

1)take the pulse in afforesaid lifeless limb prior to changing positions. It will be strong.

  1. check lifeless limb for signs of poor blood flow (coolness, pallor, bluish tone in extremities). You will find none.

3)Carefully note the distribution of your loss of cutaneous sensation in the affected limb. For me, if I put pressure on my elbow compressing the ulnar nerve, I note a characteristic loss of sensation in my pinkie and the pinkie-side 1/2 of my ring finger (in addition to other lost sensation). If I fall asleep with my arms over my head, allowing my massive triceps to compress my radial nerve, I note that the sensory loss is in a radial nerve distribution.

AFAIK there is a wake-up mechanism. However, it can fail in the setting of intoxication giving rise to permanent disability. For an example, see this page on Saturday Night Palsy

::looks for other responses on preview…whew::

Although nerve compression is almost certainly causing your pins and needles, poor circulation can do this as well. “Stocking and glove” pins and needles are sometimes seen in long-time diabetics.

If you did not wake up right away, it simply would have taken longer to get back to normal in the morning. People with carpal tunnel syndrome can feel that way all the time.

So how do you know if your circulation is poor? One way is to pinch a fingernail between thumb and index finger (of the other hand) until it turns white. It should take less than two seconds or so to return to normal colour.

Another test is to squeeze your wrist tightly with the opposite hand. Make a fist and then extend the fingers of the squeezed hand, several times, until the palm starts to turn white. Then release the pressure on the wrist ONLY on the side of the little finger. This obscures the ulnar artery, but the hand should still turn pink due to blood from the radial artery on the thumb side. Repeat this and release the pressure on the thumb side to block the radial artery, and prove the ulnar artery is patent.

These are known as the “capillary refill” and Allen’s tests.
They can also be done on the foot.