The Problem with Giving Blood

As some of you might know today was the blood drive. I have no idea how many of you have given blood before but today I found quite possibly the largest flaw in it of all the issues they deal with. Today I made it through all the tests, my iron was acceptable, my pulse and blood pressure were not too high, all the questions I had to answer checked out fine, and I made it through the worst part of the procedure, which is most definitely the finger prick. Next we went to the little bed like stretchers, I have no idea what to call them, to get ready to give blood. There everything went fine as well, they found a good vein and got the needle in, and the blood started flowing out of me steadily, but then everything went wrong. My blood flowing through the tube really started to slow down and after about five or ten minutes I was told that they were sorry but my blood had clogged in the tube or needle and therefore what blood I had given would not be able to be used. Now this really frustrates me, it is not as much the hour of time I spent going though preliminaries to give blood, I could have easily been denied right at the end for not having good enough veins or one of those generic problems, but I have no idea how much blood I pumped into that bag. The idea that their system allows however much blood I managed to pump out, I am assuming I at least filled the bag half way, gets destroyed really irritates me. One would think that they would have developed a system by now which allows for the use of different amounts of blood. Currently I know that they already have chemicals in the bags to make the blood usable, so the blood can only be used if you fill the bag, but wouldn't it make much more sense to add the chemicals later in some special plant so as to not waste potentially hundreds of pints of blood which clots up halfway through the procedure or can not get it pumping quickly enough? How can they be happy with this enormous loophole in their system? The entire thing seriously irritates me so I am asking one of you, at least one of you I assume plans to be some sort of doctor, to fix this large problem and to make the system work better, to save potentially huge quantities of blood, to help the world. If you need somewhere to get started I would think that the chemicals could be maxed out in the back with the amount needed to prepare the entire bag, but still separated inside the bag and able to be carefully pumped in so as to prepare lower amounts as well.