Blood transfusion is an indispensable element of modern medicine which saves millions of lives a year. Learn about this incredible treatment and how it has evolved with our understanding of the nature of blood and the circulatory system.
Introduction
Blood transfusion is “the transfer of blood or blood products from one person (donor) into another person’s bloodstream (recipient),” and is an indispensable element of modern medicine which saves millions of lives a year, usually in situations where serious blood loss has occurred.
While the basic techniques involved in blood transfusion are relatively simple, and the earliest recorded research on blood transfusion dates to the 1600s, the first successful attempt in practice wasn’t until only 200 years ago. This was largely due to the lack of understanding and adequate knowledge on the nature of blood and the physiology of the circulatory system.
Ancient Times
There is a plethora of ancient tales and written accounts to suggest that people have been fascinated by blood and its significance throughout history, with many cultures recognizing its regenerative properties long before blood transfusion was possible.
In Homer’s *Odyssey*, written around 700 BCE, Odysseus gave the ‘shades’ in the underworld blood from a sacrificed animal which allowed them to communicate with him. Ancient Egyptians practiced *bloodletting* to cure sick patients, which involved cutting open a vein to release the disease as in those times sickness was simply perceived to be ‘bad blood.’ This practice long continued with the Romans and the Greeks, with Hippocrates theorizing that disease was, in most cases, an imbalance in the blood.
In those times, as healers began to recognize the importance of blood in one’s health, attempts to replace lost or diseased blood were performed by giving patients blood to drink from a fit and healthy person or animal.
The Circulatory System
The earliest known written account on the circulatory system can be found in the *Ebers Papyrus*, a compilation of Egyptian medical texts dating back to the 16th century BCE. The text contains an accurate description of the circulatory system, acknowledging the connection between heart and arteries, but is flawed in the belief that it was air circulating through the veins.
The first major leap in our understanding of blood that made blood transfusion conceivable wasn’t until the 17th century when British physician and anatomist William Harvey discovered the circulatory system in 1628. Harvey discovered that blood has its own pathway through the body and demonstrated that all of the body’s organs and tissues are supplied by oxygen. He also showed for the first time that the body simultaneously processes oxygen-rich and oxygen-lacking blood without mixing the two.
The First Blood Transfusions
The accurate understanding of the physiology and function of the circulatory system was demonstrated in 1628 by William Harvey. As a result, the first blood transfusions were attempted in the mid-1600s, though most often unsuccessfully in humans.
In 1665, British physician Richard Lower performed the first successful blood transfusion from one dog to another, then, in 1667, French physician Jean-Baptiste Denis performed the first ever direct blood transfusion to a human by transfusing blood from a sheep to a sick 15-yr old boy, and later repeated the same to another patient with both surviving. Further attempts though failed and proved fatal.
Soon after, blood transfusions were banned by the French parliament and no longer pursued by the Royal Society in London as they were deemed too dangerous, and the procedure ceased to be used until the mid-19th century.
The 1800s – First Transfusion of Human Blood
The first blood transfusion from one human to another occurred in 1818 by British obstetrician James Blundell at Guy’s and St. Thomas’ Hospital in London. Blundell used blood transfusion on a woman for the treatment of postpartum hemorrhage. Prior to that, and throughout history, a large percentage of women died during childbirth due to the loss of large amounts of blood.
Blundell was successful with his first transfusion using the woman’s husband as donor, and he reported his success and findings in a paper to the Medico-Chirurgical Society of London which was presented on 22 December, 1818. This signaled the beginning of a new era of blood transfusions in modern medicine.
However, while Blundell was successful in his first attempt, his subsequent attempts weren’t as positive. He was undoubtedly the first to understand that human blood is needed to be used on other humans, but it wasn’t yet known that there are different blood types, and that a transfusion with the wrong blood type can lead to immune rejection and, often, death.
The Discovery of Different Blood Types
In 1901, Austrian doctor Karl Landsteiner discovered the existence of different blood groups, and blood transfusion became a safer practice. Landsteiner discovered the A, B, and O blood groups and theorized that *agglutination* (the clumping of particles) occurred when two incompatible blood types were mixed. As a result, he established a blood type classification system based on the unique chemical composition of red blood cells.
Two years after Landsteiner’s discovery, his colleagues discovered the AB blood group and concluded that all 4 blood groups were mutually incompatible. In 1912, Roger Lee and Paul Dudley White determined that O type blood could be transfused into any other blood type, and that AB recipients could receive blood of any type. In 1907, American surgeon Reuben Ottenberg established the process of patient/donor blood cross-matching prior to a blood transfusion procedure.
Blood Types – A Brief Description
A person’s blood type entirely depends on the genes they inherited from their parents and the best-known system for categorizing blood types is known as the ABO system. The 4 major blood types are A, B, O, and AB, which are further split into 4 sub-categories: A+/A-, B+/B-, O+/O-, and AB+/AB-. The most common blood type is O+, while the rarest is AB-.
The differentiation between blood types lies in the *antigens* that are on the surface of the red blood cells. Antigens are protein or sugar molecules which vary from person to person due to genetic differences. The difference in the antigens of each blood type determines the compatibility between blood donor and receiver. Incompatible blood types will launch an immune response from the receiver and lead to rejection of the transfusion.
People with O- blood type are considered universal donors as almost anyone with any blood type can receive O- in a transfusion.
The Impact of War
Blood transfusions took off in the early 20th century following the fundamental discovery of the different blood groups and which ones were compatible and could safely be mixed. When WWI broke out in 1914, the need for continuous supply of fresh blood to save wounded soldiers led to the creation of blood banks.
Efficient blood banking required methods to allow for longer preservation of blood, which led to the discovery of sodium citrate as a successful chemical with potent anti-clotting properties. Sodium citrate kept blood fresh while refrigerated, which made it possible to store and later transfuse blood from dead soldiers, saving thousands of lives.
Following the successful blood preservation and storage during WWI, the 1920s and ‘30s saw the beginning of voluntary blood donations which could be stored and used as needed, and, by the start of WWII, blood transfusion was a well-established procedure which was used on a large scale to treat thousands of injured soldiers.
Modern Advances
Today, scientific advances in how the blood works have made blood transfusion safer than ever before. *Nucleic acid amplification testing* (NAT), which is a type of molecular testing, finds active viruses in the donor’s blood to determine infection risk. If an active virus is found, then the donor blood is discarded.
Furthermore, advances are being made in avoiding and treating reactions occurring from blood transfusions, including transfusion-related lung injury (TRALI) and transfusion-associated cardiac overload. Researchers have found that modifying the blood prior to transfusion by removing white blood cells can reduce the likelihood of host rejection.
