Blood transfusion is the taking of blood or blood-based products from one individual and inserting them into the circulatory system of another. It can be considered a form of organ transplant. Blood transfusions may treat medical conditions, such as massive blood loss due to trauma, surgery, shock and where the red cell producing mechanism (or some other normal and essential component) fails (see blood diseases).
Great care is taken to ensure that the recipient's immune system will not attack the donor blood, and also to avoid transfusing white blood cells that could initiate an immune attack on the host (graft versus host disease). Nevertheless, blood transfusion does suppress the immune system, increasing the risk of complications after surgery.
In addition to the familiar human blood type (A, B, AB and O) and Rhesus (positive or negative) classifications, other red cell antigens are known to determine compatibility, to one degree or other. These other type become increasingly important in people who receive many blood transfusions as their bodies develop increasing resistance to blood from other people.
There is increased awareness that a number of diseases (such as AIDS, syphilis, hepatitis B and hepatitis C and others) can be passed from the donor to recipient. This has led to strict human blood transfusion standards in developed countries. Standards include screening for potential risk factors and health problems including determining donor haemoglobin level, and answering a set of standard oral and written questions, as well as testing donated units for these infections. The lack of such standards in places like rural China, where desperate villagers donated plasma for money and had others' red blood cells reinjected, has produced entire villages infected with the AIDS virus.
The process of donating blood takes about 45 minutes. About 450 ml (¾ pint) is taken. Afterwards, donors should have moderate volumes of non-alcoholic drinks, to help restore their blood volume back to normal. This generally occurs within a few hours. The donor's body replaces other components of the blood, such as platelets and red cells within a few days or weeks.
The contraindications to a blood donor include:
- previous malaria or hepatitis.
- history of drug abuse
- donors who have received human pituitary hormone.
- donors with high risk sexual behaviour
- donors who have previously been transfused (depending on geographic location)
Sometimes only parts of the blood are taken as a donation. Blood is made up mostly of plasma, red blood cells, white blood cells and platelets. Plasma and platelets can be donated separately in a process called ~apherisis. Blood is usually separated into components after being donated to make the most use of it. Donation of whole blood is generally reserved for treating young children and remote areas where the hospital summons donors when it needs them. Resulting blood component products also include albumin protein used to treat burns, clotting factor concentrates used to treat hemophilia, cryoprecipitate, fibrinogen concentrate, and immunoglobulin antibodies for immunological disorders.
Donation of whole blood eliminates transfusion-related risk of illness for the blood donor, aside from the minuscule chance of infection or perhaps of localized injury to the donor site. While there is a theoretical risk to the donor when they donate plasma and have red cells reinfused, this risk is eliminated by proper sterilization procedures. However, this caused public health disasters in China where this practice was often unregulated. Modern well run blood plasma collection centers are completely safe. In the United States and other developed countries, they are maintained by pharmaceutical companies, using paid donors; in the U.S. up to twice-weekly.
Donations are usually anonymous to the recipient, but products in a blood bank are always individually traceable through the whole cycle of donation, testing, separation into components, storage, administration to the recipient. This enables management and investigation of any suspected transfusion related disease transmission.
Animal Blood transfusion
Verterinarians also administer transfusions to animals. Various species require different levels of testing to ensure a compatible match. Cats have 3 blood types, cattle have 11, dogs have a dozen, pigs 16 and horses have 34.
The rare and experimental practice of inter-species blood transfusions is a form of xenograft.
There are currently no clinically acceptable oxygen-carrying blood substitutes, however, there are widely available non-blood volume expanders and other blood saving techniques. These are helping doctors and surgeons avoid the risks of disease transmission and immune suppression, address the chronic blood donor shortage and address the religious objections of Jehovah's Witnesses. A number of blood substitutes are currently in the clinical evaluation stage. Most attempts to find a suitable alternative to blood have so far concentrated on cell-free haemoglobin solutions. Blood substitutes could make transfusions more readily available in emergency medicine and in pre-hospital EMS care. If successful such a blood substitute could save many lives, particularly in traumas where massive blood loss results.
Papst and other Catholic authors take pains to discredit the contemporary chronicler Stefano Infessura's story of Innocent VIII's deathbed. As the Pope sank into a coma, the harrowing story was told that, at the suggestion of a Jewish physician, the blood of three boys was infused into the dying pontiff's veins. They were ten years old, and had been promised a ducat each. All three died. Historians of medicine note this event as the first reported historical attempt at a blood transfusion.
World War II syringe for direct interhuman blood transfusion
With Harvey's discovery of the circulation of the blood, more sophisticated research into blood transfusion began in the 17th century, with successful experiments of transfusions between animals. However, successive attempts on humans continued to bring death.
The first fully-documented human blood transfusion was administered by Dr. Jean Baptiste on June 15, 1667. He transfused the blood of a sheep to a 15-year old boy (the boy later died, and Baptiste was accused of murder).
Only in the first decade of the 19th century was the reason for such death found in the existence of blood types, and the practice of mixing some blood from the donor and the receiver before the transfusion allowed a greater number of successes.
While the first transfusions had to be made directly from donor to receiver before coagulation, in the 1910s it was discovered that by adding anticoagulants and refrigerating the blood it was possible to store it for some days, thus opening the way for blood banks.The first blood transfusion using blood that had been stored and cooled was preformed on January 1, 1916. It was performed by the Royal Army Medical Corps (RAMC), the procedure was very successful.