The following key points should be always borne in mind
when transfusion of blood and blood products is planned:
1.These components may be processed further by, for
example:
o Leukocyte (white cell) removal
o 'Pooling' (combining platelets separated from 4 to 6
donations to produce a therapeutic dose for an adult
patient), as shown in the Figure 14.2.Cryoprecipitate, prepared from fresh frozen plasma,
which is rich in Factor VIII and fibrinogen
Plasma derivative: Human plasma proteins prepared
under pharmaceutical manufacturing conditions, such as:
o Albumin
o Coagulation factor concentrates
o Immunoglobulins
* Apheresis: a method of collecting plasma or platelets
directly from the donor, usually by a mechanical method
WHOLE BLOOD
Whole blood is obtained from human blood donors by
venesection.The biochemical and metabolic effects
of storage are as follows:
o Reduction in the pH (blood becomes more acidic)
o Rise in plasma potassium concentration (extracellular
K+)
o Progressive reduction in the red cell content of 2,3
diphosphoglycerate (2,3 DPG) which may reduce the
release of oxygen at tissue level until 2,3 DPG is
restored
o Loss of all platelet function in whole blood within 48
hours of donation
o Reduction in Factor VIII to 10 to 20 percent of normal
within 48 hours of donation.Coagulation factors such
as VII and IX are relatively stable in storage
Advantages of Whole Blood
o Requires only simple and inexpensive single collection
packs
o No special equipment is needed for processing
o For patients with hemorrhage, whole blood supplies
red cells,volume and stable coagulation factors.Whole blood must be collected, tested and processed
to high safety standards
BLOOD COMPONENTS / BLOOD PRODUCTS
Whole blood may be suitable for transfusion in many
clinical situations, such as red cell replacement in acute
blood loss where there is also hypovolemia.Plasma derivatives are made by a pharmaceutical
manufacturing process from large volumes of plasma
comprising many individual blood donations.Factors VIII and IX and immunoglobulins are also
made by recombinant DNA technology and are often
favored because there would be no risk of transmitting
infectious agents to the patient.The preparation of blood components allows a single
blood donation to provide treatment for two or three
patients and also avoids the transfusion of elements
of the whole blood that the patient may not require.DEFINITIONS
Whole blood: Unseparated blood collected into an
approved container containing an anticoagulantpreservative
solution.During donation, blood is collected into a
sterile, disposable, plastic pack which contains an
anticoagulant-preservative solution.However,
the separation of whole blood into its constituent
components--red cells, platelets and plasma--is widely
practiced for use when these specific components only
are required.The process of separation requires specialized plastic
bags, more equipment, a higher level of expertise and
more work to ensure the quality of the components
produced.This solution usually
contains citrate, phosphate, dextrose and often adenine
(CPDA).There are variations in the volume of blood collected
and the type of anticoagulant-preservative solution used
in different hospitals.An infectious agent present in the donated blood may
be transmitted to all recipients of the components
prepared from a single donation.Plasma can transmit most of the infections present
in whole blood and there are very few indications
for its transfusion.A constituent of blood, separated from whole blood,
such as:
o Red cell concentrate
o Red cell suspension
o Plasma
o Platelet concentrates
2.During storage, metabolism continues in the red cells
and platelets, while some plasma proteins lose their
biological activity.Disadvantages Whole Blood
o For patients at risk of circulatory overload, whole
blood contains a higher volume than red cell
concentrate.When the plasma is removed from whole blood, the
red cells can be used as a red cell concentrate or can
be formed into a red cell suspension by the addition of
an additive diluentPlasma or platelets collected by apheresis
3.Safe blood products, used correctly, can be lifesaving.Each unit should be tested and labelled to show its
ABO group and its RhD group.Whole blood can be transfused to replace red cells
in acute bleeding when there is also a need to correct
hypovolemia.Blood components can also be collected by apheresis.However, even where quality standards are
very high, transfusion carries some risks.If standards
are poor or inconsistent, transfusion may be extremely
risky.No blood or blood product should be administered
unless all nationally required tests are shown to be
negative.They
must be tested to minimize the risks of transmitting
infection.2.3.4.5.6.7.8.