Component Preparation
There is no indication for the routine use of whole blood. The clinical
needs of patients are best met by transfusing an appropriate
combination of various blood components. Therefore, Canadian Blood
Services separates whole blood donations into specific cellular and plasma components.
Whole blood donations are collected into various closed, multiple bag systems that allow blood components to be transferred aseptically between bags. Up to three of the four main blood component types can be prepared with each donation.
Universal Leukoreduction
Leukoreduction is a process in which the majority of white blood cells are removed from blood components. Reducing donor leukocytes helps prevent non-hemolytic febrile transfusion reactions, alloimmunization to HLA antigens, and transmission of leukocyte-borne viruses such as cytomegalovirus (CMV). In Canada, red cell, platelet and some (but not all plasma) units undergo prestorage leukoreduction.
The Component Mix
The component preparation process chosen depends on component inventory requirements. For example, if red blood cell and plasma components are required, then the donation is collected into a multiple bag system with an integral whole blood filter for leukoreduction. First, whole blood is filtered to to reduce the number of leukocytes. Next, the filtered whole blood unit is centrifuged using carefully controlled centrifugation speeds and temperatures to separate the red cells from the plasma. Plasma is then expressed into one of the satellite bags. With CP2D/AS-3 systems, as much plasma as possible is expressed (without contaminating the plasma with red cells) and then AS-3 (Nutricel®) solution is added to the red cells to produce an AS-3 Red Blood Cell, LR (Leukocyte reduced by filtration). The plasma can be promptly frozen to preserve coagulation factors and produce Fresh Frozen Plasma or Frozen Plasma depending on how soon after collection it was frozen. Alternatively, the plasma can be further processed to produce Cryoprecipitate and Cryosupernatant Plasma.
The simple schematic below shows the use of a quadruple plastic bag system using CP2D and AS-3. Note the unit has already been leukoreduced by filtration, and the plasma has been removed to a satellite bag. AS-3 must now be added to the red cells.
On the other hand, when component inventory needs call for platelets, random donor platelets can also be separated from a single unit of whole blood collected in CP2D. In this case, leukoreduction occurs after the separation of red cells and plasma as the whole blood filter for leukoreduction also removes the platelets (not shown).
Buffy Coat Production Method (BCPM)
The implementation of the Buffy Coat Production Method (BCPM) introduces two new bag systems, B1 and B2, for use in two new production methods, BCPM and the Whole Blood Filtration Method (WB), respectively. In both cases, whole blood is collected into CPD (replaces CP2D).
The B1 pack (also known as the "top and bottom" pack) is centrifuged to produce platelet-poor plasma, red cells and buffy coat from which platelets will be separated. The B2 (or regular) pack is centrifuged to produce plasma and red cells much like our current method for RBC/plasma production.
After centrifugation the whole blood is loaded into a component separator (Compomat G4) for separation of RBC and plasma. In the BCPM method, the separated buffy coat is further processed to produce platelets. SAGM (replaces AS-3) is added to the RBC product, which is then filtered to produce SAGM Red Blood Cells, LR.
When preparing platelets, four buffy coats are pooled with the plasma from one of the units; this pool is then centrifuged, the residual white and red blood cells are discarded and the remaining platelet rich plasma is further leukoreduced by filtration. The result is a pooled platelet concentrate.
See Buffy Coat Production Method for much more information about this new method. Below is a simple schematic showing the BCPM and WB methods.
