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TIDBITS® Gets A

BLOOD TRANSFUSION

by Janet Spencer

The average human has about 5 quarts of blood, and 60,000 miles of blood vessels.  A single blood cell completes a circuit of the circulatory system in about 30 seconds. Come along with Tidbits as we get a blood transfusion!

TO THE RESCUE

•  For centuries, doctors tried to heal illnesses through blood-letting, feeling that sickness was caused by imbalance of the body’s fluids and that draining blood would help. Blood-letting didn’t fall out of favor until Louis Pasteur, Joseph Lister, and Robert Koch proved that disease comes from microbes. Now physicians began studying what happened when you added blood to a sick or injured person instead of subtracting it.

•  In the early 1800s, London obstetrician James Bundell worried about the number of women who died of blood loss after giving birth. He experimented with blood transfusions and made several discoveries: First, that only human blood should be transfused into other humans, and not animal blood; second, that blood transfusions did not cure any illness aside from blood loss; third, that transfusing blood into someone who was dead would not revive them. However, Blundell never understood why some transfusions were successful and others a failure, often ending in death.

•  Austrian pathologist Karl Landsteiner researched why blood transfusions would sometimes kill the recipient, and other times would save them. In 1901 he took blood samples from various people and added them to blood samples drawn from other people. Sometimes the red cells clumped up, sometimes they burst, and sometimes nothing happened. Landsteiner first thought that some blood was “sick” and other blood was “healthy” but  further research showed that there were different types of blood, which he labeled type A, type B, and type C. He then studied the different blood types, laying the groundwork for much that was to come.

•  A red blood cell is shaped like a flattened donut without the hole. A protein inside the red blood cell called hemoglobin collects oxygen in the lungs, delivers it to the body’s cells, and then carries carbon dioxide away, to be exhaled through the lungs. But there are different types of red blood cells, determined by different types of proteins that adhere to the outer surface of the flattened donut, like different types of sprinkles: Type A blood has a certain kind of proteins that stick to the outside of the red blood cells, and Type B blood has a different kind of proteins sticking to the cells. If a person with Type A blood receives Type B blood in a transfusion, or vice-versa, it triggers an immune response.

•  Landsteiner thought Type C blood had a third kind of protein sticking to the red blood cells, but later found it has no proteins sticking to it at all—it’s a flattened donut without any sprinkles. Then he found a fourth kind of blood, which had both Type A protein and Type B protein adhering to it. He called this Type AB blood. Landsteiner realized he needed to re-name his Type C blood in order to indicate that this type of blood has no proteins sticking to it at all. He re-named it Type O.

•  Since Type O blood has no proteins, it can be given to people of all blood types without triggering an immune response, since it’s the proteins that act as the allergen. Type O blood is called the “universal donor.” People with Type AB blood do not suffer ill effects when they receive Type A blood, or Type B blood, or Type O blood, and they are known as “universal receivers.”

•  Landsteiner was studying the blood of rhesus monkeys when he found that some of them had another type of protein adhering to their red blood cells, while others did not. He then found that humans also either did, or did not, have that identical protein. He called this new protein “the Rh factor” after “rhesus.”

•  People who are Rh positive cannot receive blood from donors who have Rh negative blood, and the other way around as well. In fact, women who were Rh negative often had trouble when they were pregnant with Rh positive babies until it was discovered that an injection of a blood product called Rh immune globulin would prevent problems. The discovery of the Rh factor brought the number of blood types to eight.

•  The most common blood type in humans is O-positive (37.4%) and the rarest blood type is AB-negative (0.6%).

•  Landsteiner also discovered that he could find out a person’s blood type from a single drop of dried blood, laying the groundwork for forensic science. Later it was found that blood types are inherited from parents in predictable patterns, leading to the ability to find out who the father of a child was likely to be. Landsteiner won the Nobel Prize for his work.

•  Dr. Reuben Ottenberg at Mount Sinai Hospital discovered how to easily cross match a patient’s blood type to the blood type of the blood donor. Blood typing became common in the 1920s.

•  Why are there four different blood types? It’s because of genetic mutation and evolution.  Type A blood is the most ancient, and all humanoids had Type A blood as the species began to evolve. Around 3.5 million years ago, Type B blood was a genetic mutation, followed a million years later by Type O. The reason these mutations flourished and were passed down through successive generations has to do with disease resistance.

•  Cells infected with malaria don’t stick well to Type O red blood cells, so people who have Type O blood are less affected by malaria and have better odds of surviving in order to pass on their blood type to their children.  Similarly, people with Type AB blood are more resistant to cholera. Gradually entire populations where cholera was common began to have largely Type AB blood, while people who lived in malaria-prone areas had mainly Type O blood.

FURTHER ADVANCES

•  The advent of World War II prompted the invention of blood banks. Doctors in Russia pioneered the practice of shipping stored blood to the battle front so that blood would be taken to the wounded soldier instead of the wounded soldier being taken to the hospital in order to receive blood.

•  Plasma is the amber liquid component of blood that transports red blood cells. Plasma can be easily freeze-dried, shipped long distances, stored for long periods at room temperature, and reconstituted with sterile water. Plasma can be transfused into any human regardless of their blood type. Red blood cells must be handled gently and kept either refrigerated or frozen. Therefore plasma is commonly used for transfusions involving cases of trauma, hemophilia, and burns, while whole blood is transfused only in cases of excessive blood loss.