Tops ... if you want any more info PM me ... I was the manager at the Southampton Apherisis clinic for 5 years and worked for NHS(Blood & Transplant) for 15 years when I left the mob ... but basically
less than 4% of the population are blood donors and even less are Apheresis donors
Red Cells (normal blood donation) they collect 450mls and then process it nominally into 2 units - Plasma mostly goes in the bin as we've all got Mad Cow Disease - after splitting RBC's are kept at 4C and lasts for 35 days. Donors donate 3 or sometimes 4 times a year as it takes about 12 weeks to replace the red cells.
However Platelets - two ways of gettting them they can take 4 donations (all same group) and take off the buffy coat (bit where the platelets are) - mix 'em together for 1 Adult Therapeutic Dose of Platelets. Problem there is if one of the donors has a "undeclared infection" ... e.g. I've got a cold but it doesn't matter" there is four times the risk to the patient ... and given that most platelets are used in Leukaemia treatment then they are more susceptable to infections so not good odds!
The other way is by Apheresis which is basically a big centrifuge ... suck blood in and spin it down so it splits into Red Cells ... Plasma and the Buffy coat ... if you know the weight and haematocrit of the donor then you know where its going to split in the centrifuge so a carefully lined up tube and the buffy coat can be taken off and the donor gets everything else back. Dependant on the donors platelet count the machines can get 2 or 3 adult thereapeutic doses from one donor so the risk to the patient is a lot lower. - 4 x donors for 1 ATD and 4 times the risk of infection against 1 donor for 2 - 3 ATD's and a quarter of the risk! The longest they can put you on a machine for is 90 minutes but depending on what dose they want (2 or 3) and your platelet count it could be less. The other thing to mention is the Citrate reaction ... they use citrate to stop the blood clotting in the machine and some of it comes back to you so you get a metalic taste in your mouth and it can make your lips tingle.
We can keep platelets for 7 days (they are all extended life these days) and they cant cope with being chilled (they go to sleep and don't wake up) so we have to keep them at 22C and constantly moving ... problem is they are suspended in a small amount of plasma ... and if you want to grown every bug known to man use plasma ... it'll grow anything ... so the risk of infection is high - hence the questionaire you fill out every time you donate! You can give platelets every 2 weeks but normally once a month.
Have a look at
Give Blood - Component Donation
As for the pretty nurse at your beck and call ... don't bank on it!
Forgot to add ... you get tissue typed at the same time as occasionally they have to match specific donors to patients.
If you've got the time to spare its a good thing to do!
