Blood Donation – where does your pint go?

July 4, 2012

Article by Global Pre-Meds
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Blood donation has come a long way since the very first one in 1665 (a human was given some lamb’s blood in the hope that it would calm him down) and even since they first became relatively routine, around one hundred years ago. A lot of work had been done on blood grouping before that, but it wasn’t until an effective – and more importantly, non-toxic – anticoagulant was discovered that blood banking could really take off. Early transfusions were of whole blood and could sometimes have fatal results, especially if the patient had had several transfusions before and had developed an antibody. Nowadays, cross matching techniques are very sophisticated and blood donations are screened for far more blood groups than the well-known ABO so reactions are generally rare.

As a donor, you might give whole blood or possibly you might be asked to donate plasma or platelets only. The advantage of the latter two is that the volume is much smaller and the red and white cells (and plasma, in the case of platelet donation) are returned as the donation progresses, so you can donate more often with no ill effects. Whole blood donations – usually 450 ml or 1 pint – are sometimes left as they are donated and sometimes they are divided into their component parts in the blood transfusion laboratory before being sent out to hospitals for donation. The life of a whole blood donation is around a month and sometimes one bag can be cross matched many times before it is actually given. A well run blood bank will waste very little blood by keeping an accurate inventory and making sure that stock is rotated.

Plasma is perhaps the most useful part of a donation, as it can be divided into so many fractions, each with a specific use, in clotting, to create Anti-D, immunoglobulins and many more. It can also be frozen, which of course increases its useful shelf life enormously. Concentrated red cells, from which the plasma has been removed, are normally used in cases of anaemia as the recipient will get what they need without a large fluid load. White cells can be taken off as well and can be given to anyone with a compromised immune system or anyone who has had radiotherapy to deliberately kill bone marrow in cases of malignancy. One pint of blood can go a very long way, in fact.

Many people when thinking about the typical use of a pint of donated blood immediately think of road traffic accidents and other trauma but in fact this accounts for only around 2% of all donated units. The biggest area is in cancer treatment – usually blood products – with non-malignant anaemias using around 20%. Surgery accounts for another 30%, if you count obstetrics in that group and various other medical situations use the rest – usually in a planned way. One way or another, though, very little is wasted and donating blood is still a very worthwhile thing to do, which can really make a difference.