transfusion
Meaning of transfusion: Rarely whole blood any more: a donation is split into parts so each patient receives only the component that is missing.
Definition of transfusion
Transfusion is the transfer of blood or one of its separated parts from a donor into a patient through a vein. Whole blood is seldom given as collected; it is separated into red cells, platelets and plasma so that each recipient receives only what is needed. Testing for compatibility comes first, because mismatched red cells provoke an immediate immune attack.
What is actually given?
| Component | Replaces | Typical reason |
|---|---|---|
| Red cells | Oxygen-carrying capacity | Blood loss, or anemia causing symptoms |
| Platelets | The cells that plug small leaks | A low platelet count with bleeding, or before a procedure |
| Plasma | Clotting proteins together | Bleeding with several clotting factors depleted |
| Cryoprecipitate | Fibrinogen chiefly | Low fibrinogen during major bleeding |
Splitting a donation this way lets one donor supply several patients, and spares each of them volume they do not need. Every component is stored differently and keeps for a different length of time, which is why platelets are the scarcest and red cells the most available. A whole blood transfusion in the original sense now belongs mainly to massive bleeding, where blood lost in balance is best replaced in balance.
Why does matching matter so much?
Because the immune system reads a red cell as either its own or foreign, and reads it instantly. The cell surface carries markers, and the ABO blood group system is the one that matters most, because people carry ready-made antibodies against the groups they lack without ever having met them. Blood of the wrong group is destroyed within minutes, and the wreckage can injure the kidneys and set off clotting throughout the circulation. The Rhesus D marker behaves differently. Antibodies against it form only after exposure, and once formed they cross the placenta and threaten a future pregnancy. The laboratory pairs a patient sample against the unit, but the sample has to belong to the patient, and errors reaching a patient are usually errors of identity at the bedside rather than failures at the bench.
What reactions are recognized?
Fever and shivering with no incompatibility at all is the commonest, caused by immune debris in the unit. Itching and hives come next. The serious reactions fall into three groups: destruction of the transfused cells by antibody, more volume than a strained heart can move, and a sudden lung injury peculiar to transfusion. Delayed reactions surface days or weeks later, when an antibody formed during an earlier exposure rises again. Transmission of infection has grown uncommon where donations are screened and tested, so the risks shaping practice now are immune and clerical rather than infectious.
Also known as
Used in a sentence
Transfusion of two units of red cells was given for symptomatic anemia.
Good to know
Incompatible transfusions usually follow misidentification of a patient or a sample rather than laboratory error, and recognized reactions range from fever alone through destruction of the transfused cells, circulatory overload and acute lung injury.
Word origin
Where “transfusion” comes from
From the Latin trans-, meaning across, and fundere, to pour.