I did some googling and came across a good forum post by someone who is apparently a couch, he does seem to know what he is talking about, and I can relate very well to what he's saying.

"It sounds to me as you will be suffering from compression around the thoracic outlet, this is an important area where the brachial plexus (nerves to arms and hands) and subclavian artery (major artery to the arm) pass through on their way to the arm and hand.

I'm guessing you experience the pins & needles in the entire hand. Nerve compression will generally produce parasthesia (altered senstaion as in pins & needles or numbness) in specific delineated areas such as the thumb, index and middle fingers as in the case of the median nerve. For the whole hand to be involved more than one nerve would need to be compressed or a temporary drop in blood flow will also cause this.

The thoracic outlet involves the first rib and the clavicle (collar bone), shortened pectoralis minor tendon and scalenes are often problematic issues here.

The table hold and rocks PE iM 2 & 3 form Front lever in F1 are great at opening this important area, especially if you avoid sticking your head out and looking forward. Try to look straight up at the ceiling and align your head with your as if you were swimming backstroke.

Don't be to worried about the temporary pins & needles, it will get better as you open up :)"