Clinical Laboratory - Transfusion Medicine

Lifespan of Transfused Products - -
Efficacy of Transfusion

Blood products have storage times based upon the type of product and storage conditions.

Blood Collection, Preservation, and Storage

Blood is collected as whole blood, and can be stored as whole blood (with all of the plasma present) or, much more commonly, as packed red blood cells (PRBCs) in which about 70% of the plasma has been removed. This is done by light centrifugation.

The platelet rich plasma can then be expressed off, leaving packed red blood cells (PRBCs). PRBCs can be stored for up to 42 days at 1 - 6 degrees C.

The plasma can be centrifuged heavily a second time to separate the platelet rich plasma, and the supernatant plasma can be expressed into a third bag and stored as fresh frozen plasma (FFP). The remaining platelet rich plasma is utilized as a platelet pack.

A single donation of whole blood has supplied three separate components (packed red blood cells, platelets, fresh frozen plasma) that can potentially benefit three different patients.

Packed Red Blood Cell (PRBC) Survival

The average lifespan of RBCs is normally 120 days, and that maximum can be reached following transfusion. However, up to 5 to 10% of stored RBCs may be lost within the first 24 h after transfusion. This is followed by a linear disappearance curve. As storage times increase 25% or more of RBCs may be lost.

The efficacy of transfusion of PRBCs is measured with the post-transfusion hemoglobin and hematocrit with careful monitoring of the patient's vital signs for adverse reactions.

Vital signs are typically logged in 15 minute intervals, and hemoglobin and hematocrit levels are determined as a part of the Complete Blood Count (CBC).

Long-term Preservation and Storage

After the expiration date, rare or valuable packed RBC units can be "rejuvenated" with a biochemical solution that restores much of the original biochemical environment of the RBCs. The "rejuvenated" units are "washed" with isotonic saline in an automated device and then can be transfused as a saline-red blood cell suspension within 2 to 4 hours, or these units can be stored, glycerolized and frozen for up to 10 years.

Cryopreservation of RBCs is done to store special, rare RBCs for up to 10 years in a glycerol solution. The thawed units are washed of the glycerol, and by doing so are depleted of plasma and leukocytes.

Cryopreserved blood can help to maintain stores of Rh negative blood, to provide units for persons with antibodies to high-incidence antigens or persons difficult to cross-match because of multiple alloantibodies and to provide plasma-free blood to persons with IgA deficiency.

Fresh Frozen Plasma (FFP)

FFP as a frozen product can be stored at -18 degrees C for up to a year and up to 36 months when stored below -30¡C. . Each unit is 200 to 250 mL in volume.FFP contains one international unit/ml of all coagulation factors. FFP contains about 400 mg of fibrinogen per unit. Once thawed, FFP should be used immediately.

The efficacy of FFP can be monitored with coagulation testing.of the PT, PTT, and INR.

Platelets

Platelets are stored with agitation at 22 degrees C for up to 5 days. Since platelets are stored at room temperature, there is risk for bacterial contamination with bacterial growth that increases with storage time. Therefore, platelets must be used within 5 days of collection.

After transfusion, survival of platelets can be limited. Upon administration of platelets, the efficacy of treatment is measured by post-transfusion platelet count. If the count drops quickly, it is likely that platelets are being consumed rapidly and further transfusions of platelets may be ineffective