Modern transfusion prefers parts of blood, not the whole
Red cells, plasma, platelets, and clotting factors travel separately; white cells almost never do. Triggers once sat near 100 g/L hemoglobin; evidence now often waits until about 70–80 g/L because every donated unit still carries risk.
Blood transfusion puts blood products into a person’s veins to replace what illness or injury has taken. Early practice moved whole blood; modern care usually separates components—red cells for oxygen delivery, plasma for proteins and buffering, platelets and clotting factors for hemostasis—while white-cell transfusions remain rare. Whole blood has returned mainly in trauma. Before components were understood, blood was treated as a homogeneous fluid, and incompatible transfers killed many recipients. Autologous transfusion uses the patient’s own stored blood; allogeneic donation from someone else is far more common.
Thresholds have fallen. Red-cell transfusion was historically considered below 100 g/L hemoglobin or 30 percent hematocrit; because each unit brings hazards, triggers near 70–80 g/L are now usual and linked to better outcomes in many settings. Hospitalized patients who are not bleeding often receive one unit (about 450 mL), then reassessment. In 2012 some 70 percent of countries had a national blood policy and 69 percent had transfusion safety laws. Donations are typically anonymous in high-income systems yet fully traceable from collection through testing, separation, storage, and infusion so reactions can be investigated. Prosocial motives dominate donor surveys; fear and distrust deter.
After collection, centrifugation splits red cells, plasma, and platelets; plasma can yield albumin, clotting concentrates, cryoprecipitate, fibrinogen, and immunoglobulins. Apheresis can gather single components. Storage differs: red cells in a fridge near ice-chest temperatures, platelets at room warmth with constant gentle shaking, plasma deep-frozen to protect clotting proteins. WHO urges testing every donation for HIV, hepatitis B and C, syphilis, and regionally relevant pathogens such as Chagas or malaria—yet ten countries still cannot screen all units for one or more of those core infections, and transfusion-transmitted infection rates run higher in low-income settings. ABO and Rh typing remain mandatory compatibility checks. Transfusion is logistics as much as medicine: match the right fraction, at the right threshold, from a screened stranger.
Source: Blood transfusion
