Sunday, March 06, 2011

Some interesting and important facts about blood

March is Red Cross month, and the hospital is hosting a blood drive (as we do every two months). As the blood bank's donor recruiter, I have to try and raise awareness and interest and get people to sign up to donate blood. This time, the hospital management is getting more involved because it coincides with a new charity campaign they're running, so I was asked to write up some "interesting facts about blood" that could be used in our weekly newsletter and on our intranet page. I want to share them with you, and also encourage you to try donating blood - it only hurts a little bit and you're helping save lives. I see the other side of it all the time, with patients desperately needing blood and platelet transfusions, so I can tell you, it's important. Blood can't be manufactured (yet - research is making strides) and needs to come from donors. Plus, you get cookies!

Blood Facts

The very first blood transfusions were back in the 1600s and involved transfusing small volumes of sheep's or calf's blood to sick patients. Because the blood was from a different species, the patients often had fatal reactions to the transfusions. By the 1800s human blood was being transfused to patients, but because the blood would clot quickly outside of the body, the blood could not be stored, and had to be transferred directly from donor to recipient. Many of these transfusions still resulted in the death of the patient, until blood groups were discovered by the Austrian scientist Karl Landsteiner in 1901. After that point, blood types could be matched for transfusions, greatly reducing the risks.

In the 1930s, The Soviet Union was the first country to establish a system of blood banks, after discoveries showing that adding anticoagulant to blood allowed it to be stored outside the body, in refrigerators. The first American hospital blood bank was established at Cook County Hospital in Chicago in 1936. Blood was stored in glass bottles until plastic blood storage bags were developed in the 1950s.

There are four main blood types, defined by what type of antigen (carbohydrate and protein structure) is present on the red blood cells. There are two antigens: A and B. Those with the A antigen are type A, and those with the B antigen are type B. If your red cells have both, you will be type AB, and if you have neither, you are type O. The blood types are genetically determined and their distribution varies in different populations, but in the United States, approximately 44% of people are type O, 42% are type A, 10% are type B, and the rarest blood type is type AB, in only 4% of the population. Whether you are, say, O-positive or O-negative, will depend on whether you have the Rh factor, another important antigen on red blood cells. If it is present, then your type is "positive", and if it is absent, your type is "negative". Only 15% of individuals are Rh-negative.

The immune system of an Rh-negative mother who is carrying an Rh-positive fetus can become sensitized to the Rh factor, which can create problems with subsequent pregnancies. The result is babies being born with hemolytic disease of the newborn (HDN), where the baby's red cells are being destroyed by the mother's antibodies, leading to dangerously high bilirubin levels and anemia. In 1968, the first dose of "RhoGAM" was given to an Rh-negative pregnant woman - this product can prevent the mother's immune system from being sensitized, greatly reducing the risk of HDN. Blood and Rh typing is now part of normal prenatal care, so that all Rh-negative pregnant women can receive a protective dose of RhoGAM or an equivalent product.

Before blood can be transfused, the recipient will have a "type and screen" done. This test takes approximately 45 minutes and will determine the patient's blood type and check the patient's plasma for any antibodies to other blood groups. This ensures that the patient is receiving compatible blood. The "crossmatch" is when a drop of donor cells is mixed with the recipient's plasma to check for compatibility. If it is compatible, the donor unit is labeled for the patient and can be transfused.

In emergency situations, a blood bank can issue uncrossmatched blood. This happens when the patient's history and blood type are unknown and there is no time for testing before the blood is needed. In these cases, O-negative blood is always given, because it is compatible in recipients of any blood type. Once the patient's sample is available for testing, the blood bank will complete the work and make sure that no unexpected antibodies are present, and then prepare more units for transfusion that are of the same blood type as the patient.

Most blood collected in donor centers today is split into its components, rather than being transfused as whole blood. This is more efficient, because patients receive only the components they need, and one donation can save more than one life. Blood is spun in a centrifuge and separated into red cells and plasma. Red cells are used to treat anemia and blood loss, and help improve oxygen delivery to the tissues. Plasma contains clotting factors and is often used to treat hemorrhage and to quickly reverse the effect of anticoagulant medications. Other elements that can be separated from a blood donation are platelets, which are necessary for clotting, and cryoprecipitate, which is a concentrate of clotting factors.

Platelets are small fragments in the blood whose role is to form clots and stop bleeding. The average lifespan of platelets is only a few days before they lose their potency, which means that they are unable to be stored for an extended period. This is why platelets are often in short supply - donations must be steady to ensure their availability.

The American Association of Blood Banks estimates that 9.5 million volunteers donate blood each year, 20 percent of whom are first time donors. According to the 2007 National Blood Collection and Utilization Report about 16 million units of whole blood and red blood cells were donated in the United States in 2006. Every day in the U.S., approximately 40,000 units of blood are required in hospitals and emergency treatment facilities for patients with cancer and other diseases, for organ transplant recipients, and to help save the lives of accident/trauma victims.

Hopefully I've taught you something today... As usual, I welcome questions about the lab and the blood bank! For questions relating specifically to blood donation, like eligibility criteria or what to expect when you arrive, I'll refer you to the Red Cross website for first-time donors. Please consider donation, or at the very least spreading the word and asking someone else to donate. It does make a difference.

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