[Updated slightly from 2012]
The essentials are as follows (and this is the SHORT answer !):
Components come from whole blood that is split into, well, components…..so whole blood becomes Packed Red Blood Cells, Fresh Frozen Plasma, and Fibrinogen; this is one way that one donation can help three people. Platelets are usually obtained differently, via a centrifuge technique that removes the platelets and returns plasma and Red Blood Cells (RBCs) to the donor.
But the central issue is that these components are preserved and stored until use. How else would we have products to use in the Trauma Centers or – for that matter – the operating rooms for elective surgeries ? We would not !
Most unfortunately, the longer these components are stored, the less useful they are and, even when useful, the longer they may take to become effective. With the additives placed into collected blood, the RBCs can be kept for up to 42 days. Because of work done in the past – roughly – 20 years showing increased morbidity and mortality when older RBC are transfused, there has been a movement to limit use of older blood cells, and to store them for a lesser time, about 35 days. So those of us who do intensive care medicine try REALLY hard NOT to Transfuse any products unless it is ABSOLUTELY NECESSARY. There are data on what “absolutely necessary” means, but that is for another time.
I know you might think that this is obvious – why transfuse anything unless it is necessary – but sometimes what seems obvious is not.
Further, the way Blood Banks work is that they send us the OLDEST blood and blood products to use when we request components. If they didn’t do this, the products would / could go out of date and would then have to be thrown away.
So, component therapy is a pretty good response to the need for blood and blood products, not a perfect one. There are some potential downsides.
More recently, the data suggesting that the use of older blood products is problematic has been called into question. Sicker people require more blood so they get older blood, and sometimes they do poorly, developing complications including multiple organ dysfunction syndrome among others and even dying. Is this related to the age of the blood they’ve received or related to the patient’s severity of illness? Or both? Or something else, such as the stored blood not having most White Blood Cells removed around the time of collection.
More recent studies suggest that the use of older blood may not be as worrisome as previously thought (see editorial below)
Still, when a Patient is severely injured and may need more than 8 to 10 units of blood in rapid succession, a Massive Transfusion Protocol is invoked. This gets blood and blood products to the bedside rapidly and in large quantities.
We will transfuse one unit of Packed Red Blood Cells with one unit of Fresh Frozen Plasma (the clotting factors) and (more or less) one unit of platelets. Since these are stored and usually relatively old, they only work relatively well……but better than nothing.
Optimally, we would have a cadre of healthy 18 to 35 year olds walking around who would be willing to donate blood at a moments notice – warm, whole blood. This is CLEARLY the best option and our military colleagues can do this. The rest of us can’t.
Warm whole blood is fresh, un-preserved and all red cells, clotting components and platelets are completely active.
So in summary:
1. Try not to transfuse if possible unless you REALLY need it !
2. Component therapy is acceptable if it is needed, but warm whole blood is better.
3. We use component therapy because it is essentially the best we can do.
4. The age of blood is probably not all that important.
McQuilten ZQ, Cooper DJ. Age of Red Blood Cells for Transfusion in Critically Ill Pediatric Patients. (Editorial). JAMA. 2019;322 (22):2175 – 2176.