Biomedical Engineering Reference
In-Depth Information
for blood replacement in patients with depleted oxygen-carrying capacity and with
hemostatic or immune-mediated disorders as well as adverse effects of transfusion
therapy will be briefly described.
Clinical Use of Packed RBCs
Currently, when speaking in terms of blood transfusion, one mostly thinks of thera-
peutic use of packed RBCs. In view of transfusion therapy, anemia has to be char-
acterized as a pathological condition with the decreased total RBC volume in which
RBC transfusions are advantageous, or necessary [
8
] .
Peritransplant donor support.
The age and body mass of the donor and, in the
autologous setting, the character of primary disorder as well as earlier myelosup-
pressive treatment influence not only on the SC yield, but also on the peritransplant-
specific blood component requirements. Because of the large marrow volume
(around 800-1,000 mL) collected, RBC transfusions may be required in both autol-
ogous and allogeneic settings. Commonly, allogeneic donors will have one autolo-
gous whole blood or RBC unit collected 1-2 weeks before SC harvest. Allogeneic
RBCs for immunosuppressed autologous donors or children should be irradiated
(with 25 Gy/unit) in order to prevent transfusion-associated GvHD in the recipient.
Finally, in transplants that require marrow purification procedures, RBCs recovered
(by processing) may be returned to the donor [
1,
25
] .
Posttransplant blood component needs
. Depending on the medical requests (e.g.,
allosensitization, repeated transfusions, organ and tissue transplant), different type
of packed RBCs, such as washed, leukodepleted, or irradiated components are in
therapeutic use. The application of each one has numerous potential advantages, but
also has possible adverse effects. Determination of an appropriate threshold for
initiating RBC replacement (“transfusion trigger”) could help avoiding the
unjustified blood transfusion, as well as “under-transfusion” situations, i.e., the
inadequate support with RBCs [
1,
8,
9
] .
Decision whether to transfuse packed RBCs or not, is usually based on the
patient's hematocrit (Hct) and hemoglobin (Hb) values. However, rigid Hct and Hb
thresholds—as universal transfusion triggers—have been considered inappropriate
in several guidelines. Estimation of Hct and Hb does not always give a true descrip-
tion of RBC's lack because of the incorrect evaluation of total blood volume.
Consequently, quantification of Hct and Hb should not be the only consideration in
defining the transfusion trigger for RBC support [
9-
11
] . Valid decision to transfuse
should be made based on individual patient's general and cardiopulmonary status,
tissue oxygen consumption rate, etc. The exclusively use of “rigid” transfusion trig-
gers (Hct £0.30 or Hb £100 g/L) has little scientific confirmation and is outdated.
After the discovery of AIDS and hepatitis C, the number of preferred RBC transfu-
sions was clearly decreased—because the criteria for their performance became far
more rigorous. Generally, RBC transfusion is rarely justified at Hb ³ 100 g/L and is
nearly always indicated when Hb £ 60 g/L [
8,
10-
13
] .
