Blood that is extracted is supposed to travel continuously through a long tube that streches around the hospital several times before any part of it is used on the JW patient. This way, the blood is never actually "stored" since it is constantly flowing through the long and winding tube before it is eventually used.
If it travels through a short tube and is deposited in a collection vessel or other type of container, that constitutes "storage" which conflicts with Biblical principles regarding blood transfusions.
So, before undergoing surgery, JW patents should arrive at the hospital with at least 2,000 feet of 1/4" clear flexible tubing. This should give the blood enough time to flow through the tube without being used...