venta

Yesterday I went to blood donors'.

If you're the sort of person who doesn't want to read about needles and veins and so on, then stop reading now.

Having got through the preliminary checks and paperwork, and done my best to fail the iron-level test (I failed to fail it at the last second), I was called up to donate.

A youngish-looking chap (by which I mean younger than me; I must be getting old) told me he was in training and asked if it was ok if he did the sticking-needle-in parts of the job on me. I assume that I had the right to say no, I wanted a properly trained person if I felt that way. As it was, I figure people have to train on someone, it might as well be me.

Having looked at my arm, he told me I had "very nice veins". I guess you take your compliments where you can find them, and it can't be a line you can use in very many situations. Nice in this case obviously means "easily accessible" - I'm very pale, and my veins are close to the surface.

They were also doing some testing of the alcohol-wipes they use to clean donors' arms - did I mind being experimented on ? No, I didn't. So, I had my arm wiped twice, and then smeared over an agar jelly plate - I guess the idea is they then try to grow cultures on the jelly, and see which bacterial nasties hadn't been removed from my arm by the wipes. Afterwards, I got wiped down again with the alcohol stuff to remove the jelly.

Trainee-guy put the needle in my arm (I'm incurably nosey, I watch the whole process) and I have to concede it was much more painful than normal. I was wondering whether I could fairly blame the trainee, but he told me that actually all the alcohol on my skin would have acted like lemon juice in a cut. Bah. Didn't bloody warn me of that, did you ?

I've been doning blood on and off since I was a student (when I wasn't recovering from piercings, underweight, or generally disorganised), and it's slightly surprising to note that in the last couple of years the technology seems to have shot forwards. Having been more or less the same since I used to accompany parents to sessions, it's suddenly gone all hi-tech.

The pouch in which the blood is stored used to hang from a scale - when it reached a certain weight, they disconnected you - and was occasionally joggled by a nurse to prevent clogging. These days there are funky electronic weighing machines which let the donor see how close they are to completion, and which rock the pouch back and forth automatically. Instead of a nurse saying "open and close your hand, dear" a little symbol of a hand flashes redly at you.

The network of tubes leading from your arm is much more complicated, allowing them to take the samples for testing from a little reservoir rather than manually taking three extra samples from your arm.

The prick-test (done on one finger) to check for iron levels use to involve a small glass tube which sucked up blood via capillary action (I believe). These days there are small plastic disposable pipettes which are (I was told on enquiry) absolute murder to use.

It slightly surprises me, in some ways. The procedure is increasingly complicated, and the list of conditions which debar you from donating is getting ever longer and more intricate. Collecting blood donations (which, the nurse told me, only last for 35 days before they become useless) must be incredibly expensive. Yet, the procedure still relies on the rather old-fashioned idea of taking someone else's blood out of their body. It really surprises me that synthesising blood artificially isn't yet possible (or, if possible, economically viable). I guess there's probably a lot of money in that area of research.

Also, a further question: if someone cuts an arm really badly, or loses a hand, or something then the policy is to tie something tightly round their arm above the cut. I know the application of tourniquets isn't really taught to first-aiders any more, but I'm under the impression that that's because it's a bit tricky to get right. A tourniquet is still an effective way of preventing blood loss.

While you give blood, they put a blood-pressure cuff round your upper arm (above the needle) and inflate it. This has the same effect as tying something really tightly round your arm.

Now: why is it that you do the same thing to both prevent bleeding and encourage steady bleeding ? Or is it that, without the blood pressure cuff, the blood would leave a donor's arm at an unhealthily fast rate ? Must remember to ask next time I'm there.