Blood transfusion

The infusion of large volumes of blood or blood products directly into the bloodstream to remedy severe blood loss or to correct chronic anaemia. In an exchange transfusion, nearly all of the recipient’s blood is replaced by donor blood. Before a transfusion, a sample of the recipient’s blood is taken to identify the blood groups, and it is matched with suitable donor blood. The donor blood is transfused into an arm vein through a plastic cannula. Usually, each unit (about 500 ml) of blood is given over 1–4 hours; in an emergency, 500 ml may be given in a couple of minutes. The blood pressure, temperature, and pulse are monitored during the procedure. If mismatched blood is accidentally introduced into the circulation, antibodies in the recipient’s blood may cause donor cells to burst, leading to shock or kidney failure. Less severe reactions can produce fever, chills, or a rash. Reactions can also occur as a result of an allergy to transfused blood components. All blood used for transfusion is carefully screened for a number of infectious agents, including HIV (the AIDS virus) and hepatitis B and hepatitis C. In elderly or severely anaemic patients, transfusion can overload the circulation, leading to heart failure. In patients with chronic anaemia who need regular transfusion over many years, excess iron may accumulate (haemosiderosis) and damage organs such as the heart, liver, and pancreas. Treatment with desferrioxamine to remove excess iron may be needed.


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