Curriculum · Hematology
Blood components: dose and storage
What it is
A donated unit of whole blood is not transfused as it is. It is processed into separate components, and each component has its own volume, its own storage temperature, its own storage viability and its own indication. The components prepared this way are red blood cells, buffy coat derived platelets pooled from 4 units, apheresis platelets, frozen plasma, apheresis plasma and cryoprecipitate.
Volumes per unit differ: about 300 mL for red blood cells, 350 mL for buffy coat derived platelets, 330 mL for apheresis platelets, 290 mL for frozen plasma, 500 mL for apheresis plasma and only 10 mL for cryoprecipitate. What each unit carries differs as well. Packed red cells carry red cells, frozen plasma carries all clotting factors, and cryoprecipitate carries fibrinogen, Factor VIII, vWF and Factor XIII.
How it is treated
Storage temperature divides the components, and storage viability follows from it.
- Red blood cells are held at 1-6 °C, with a storage viability of 42 days.
- Platelets, buffy coat derived or apheresis, are held at 20-24 °C for 5 days.
- Frozen plasma and cryoprecipitate are held at -18 °C or colder for 1 year. Once thawed they move to 1-6 °C, and the time left is 24 hours for plasma and 4 hours for cryoprecipitate.
Pre-transfusion preparation time is not the same either: about 10-45 minutes for red blood cells, 5 minutes for platelets and 30 minutes for frozen plasma, apheresis plasma and cryoprecipitate. To any of these must be added the 45 minutes required for pre-transfusion specimen testing, so the request is made well before the product is needed.
Adult dose is written per component. Red cells are dosed by target correction, 1 unit for each 1 g rise in Hb that is desired. Platelets are given as 4-6 pooled units or as 1 apheresis unit. Frozen plasma is given as 3-4 units, and cryoprecipitate as 8-10 units.