Choosing the right blood component

What it is

Whole blood is separated into components, and each component has its own volume, storage limit, storage temperature and pre-transfusion preparation time. Red blood cells come as about 300 mL, held at 1-6 °C, with a storage limit of 42 days and 10-45 minutes of preparation. Buffy coat derived platelets, made from 4 units, are about 350 mL at 20-24 °C with 5 minutes of preparation and a storage limit of 5 days, and apheresis platelets are about 330 mL, also 20-24 °C and 5 minutes, and carry the same 5 day limit. Frozen plasma is about 290 mL and apheresis plasma about 500 mL, both at -18 °C or colder with 30 minutes of preparation, and both keep for 1 year. Cryoprecipitate is about 10 mL, also -18 °C or colder and 30 minutes, and it keeps for 1 year as well. These preparation times are in addition to the 45 minutes required for pre-transfusion specimen testing.

How it is treated

Platelet transfusion is indicated by the count together with what is to be done:

Under 10: non-immune thrombocytopenia.
Under 20: minor procedures, such as line insertion.
Under 50: major procedures, where significant blood loss is expected.
Under 100: before neurosurgery, or in head trauma.

A component can also be modified, and each modification meets a particular risk:

Leukoreduction decreases white blood cells in cellular blood products; it reduces the risks of FNHTRs, human leukocyte antigen alloimmunization and transfusion-associated CMV.
Irradiation renders T lymphocytes unable to replicate; it prevents donor cell engraftment in severely immunosuppressed transfusion recipients and prevents transfusion-associated graft-versus-host disease. Certain groups of patients need irradiated blood components for that reason.
Washing removes and replaces the acellular fluid in cellular blood products; it reduces the risks of FNHTRs, ATRs, cell-free hemoglobin and hyperkalemia.

The list is read by taking the count together with what is about to be done. Line insertion sits in the minor procedures row, so the number to reach before a line is put in is 20, not the 50 of major procedures where significant blood loss is expected, and not the 10 of a non-immune thrombocytopenia with nothing to be done.