Donating blood is a pretty simple process. You should try it if you can. Here's how it goes.
- In the interview process a questionnaire is filled out. The questions are designed to identify potential health problems for the donor or potential infections that may be present in the donor that could be transmitted through transfusion to another person.
You walk into the blood bank or bloodmobile and fill out a questionnaire. Then you wait a bit until someone comes to interview you. It's to check if you have any reasons why you shouldn't donate blood or if you would be adversely affected by the process itself.
- A fingerstick yields a drop of blood for testing to determine if the donor has a high enough hematocrit to safely donate blood.
It's only a little tiny sting, and as long as you don't actually know when they're going to stick you, you won't flinch.
- The blood is drawn into a capillary tube which is then spun in the small centrifuge (seen in the background) to determine the hematocrit.
Some donation centers will have other means to determine if your hematocrit is high enough. There are chemical "float" tests checking how fast your blood sinks, there is also a small black machine that seems to give a digital readout after a very small sample of blood is somehow inserted into it.
- The donor sits in a reclining chair. An inflatable cuff on the arm is used to check blood pressure and to maintain venous filling.
The funny sucking, whooshing sound of a sphygmomanometer is one of the coolest sounds I know of. I'm surprised nobody's used it as a percussion sound in a techno song. Just relax. This part is easy.
- The site for drawing blood is selected and disinfected. A prominent vein is chosen for the venipuncture site.
Sometimes they'll take a strip of rubber and tie it around your arm, then tell you to make and release your fist several times. This pumps up the veins in your arm so that they're more visible (and therefore easier to reach.)
- The disinfectant is applied to the area around the vein to be used.
This is usually a cotton ball that's been impregnated with rubbing alcohol. If you're lucky they won't use Betadine, which has iodine in it and makes practically indelible yellow stains on your skin. But it makes the site clean.
- The needle used to draw the blood from the vein is gently inserted.
The people who actually do the blood drawing at donation centers get so much practice at inserting the needles that they get very very good at it. As long as you don't wriggle around on the table, it involves surprisingly little pain.
- Blood fills the collection bag by gravity in a few minutes. The sealed plastic collection bag contains a blood preservative.
The worker hangs the blood from a weighted lever on a stand. When the bag fills to a certain heft, it drops and the lever pinches the collection tube shut so you don't keep trying to bleed into the bag.
- Just after the bag has filled, blood from the line is taken to fill several vacutainer tubes for further testing.
They take a little bit more blood, just in case you weren't completely honest on the interview or questionnaire, knowingly or unknowingly. It's for everyone's protection. If you watch, you can see it spurting into the vacutainers because of the relatively low air pressure inside them.
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The needle is removed and pressure is applied over the venipuncture site, then a bandage is placed for the next couple of hours.
Oooh. A band aid or a cotton ball and some surgical tape! Neato. I like it when they give me those brightly colored little bandage spots.
- The donor drinks some liquid (here a tube of apple juice) to replace the lost blood volume, eats some cookies, and is on his way in about 10 minutes.
If you go around lunch time, some blood banks will feed you with half a sandwich or something. Usually the cookies are pretty good, too. Sometimes you'll luck out and they'll give you a selection of juices.
The italicised portions of this node are drawn from http://www-medlib.med.utah.edu/WebPath/TUTORIAL/BLDBANK/BLDBANK.html There is a wonderful tutorial all about giving blood.