Biomedical Engineering Reference
In-Depth Information
Each apheresis-derived PC is prepared from a single donor by platelet apheresis
(³ 3-8 × 10
11
platelets in 150-200 mL plasma) [
8,
17,
25
] .
PCs should be administered immediately after preparation, or after storage in
liquid state up to 5-7 days on 20 ± 2°C, with permanent agitation of units using
shakers [
1,
25
]. During storage the quantity and quality of PCs is progressively
decreased. Long-term storage of platelets in frozen state requires the application of
safe and effective cryopreservation procedures [
19,
26
] . Apheresis-derived PC con-
tains 10
4
-10
6
leukocytes (i.e., £1% of leukocytes in a random-donor PCs) and less
than 0.5 mL of contaminating RBCs, demonstrating the selectivity of the collection
process. The low leukocyte content of apheresis-derived PC reduces the risk of leu-
kocyte-mediated adverse transfusion effects [
17
] .
Plasma and Coagulation Factor Replacement
Since the clinical use of fresh frozen plasma (FFP) is not free of adverse effects,
data concerning plasma constituents and replacement effectiveness in clinical situ-
ations, such as posttransplant period are essential. Also, clinicians have to be
informed about the alternative products for FFP in transfusion practice. The appli-
cation of FFP should be reserved only for clinical situations in which plasma prod-
ucts have been proven evidently beneficial, or in conditions in which more specific
replacement is not available [
30
]. Cryoprecipitate is a blood product containing fac-
tor VIII (FVIII:C), von Willebrand factor (vWF), factor XIII (FXIII), fibrinogen,
and fi bronectin [
31,
32
]. It is an insoluble cold precipitate formed when FFP is
thawed between 1 and 6 °C. Each bag of cryoprecipitate contains between 150 and
250 mg of fibrinogen, 30-60 mg of fibronectin, and 80-120 units of FVIII. In addi-
tion, cryoprecipitate also contains approximately 40-70% (i.e., 80 units) of original
vWF and approximately 30% (i.e., 40-60 units) of the initial concentration of FXIII
[
13,
16
]. The recombinant coagulation factors allow rapid reversal of bleeding epi-
sodes, and therefore limit irreversible joint damage and other bleeding complica-
tions. In practice, for the termination of spontaneous bleedings, FVIII:C plasma
activity should be improved up to the level of at least 0.30-0.60 IU/mL, and during
the surgery from 0.50 to 1.0 IU/mL. Required quantities of FVIII:C can be calcu-
lated upon the volume of patient's circulating plasma as well as the initial and the
desired FVIII:C plasma activity [
25
] .
Granulocyte Support Practice
More recent advances in granulocyte collection, with the administration of rHuG-
CSF to enhance granulocyte yield, have produced reestablished concern for this
therapy (modern granulocyte transfusion support). Granulocyte collections are
apheresis-derived. The use of rHuG-CSF has made possible markedly increased
