CLINICAL LAB SCIENEC

CHAPTER 17: IMMUNOHEMATOLOGY (BLOOD BANKING) 417
types for use in surgery and for trauma where bleeding occurs to an extent that
a transfusion is needed. Not all hospital blood banks collect their own supply of
blood for use within the facility. Those who do collect their own blood are required
to first collect, then test the units for certain antigens and sometimes antibodies,
and then to store the blood safely until it is used. However, most blood supplies
are maintained and blood is shipped regularly to hospital blood banks from large
commercial facilities that perform on-site collections around the country, such
as the American Red Cross. These facilities also provide a valuable service that
is beyond the scope of routine hospital blood banks. They determine rare blood
groups and types and provide units of blood for patients who are unable to take
the most ordinary groups and types due to atypical antibodies (alloantibodies).
Large commercial blood banks also perform emergency blood drives when
disaster strikes and have the staff and capabilities to ship this blood in refrigerated
vehicles for long distances to the scene of the disaster. One of the first
medical needs for effectively responding to injuries with blood loss is to maintain
adequate circulation by using volume expanders. Only blood can be used as a
volume expander that is capable of transporting oxygen to all the tissues of the
body. Promoting circulation and perfusion of the tissues with oxygen will prevent
shock and tissue damage that may lead to death.
Blood banks may also harvest white blood cells for those with immunological
problems and platelets for those who are in danger of bleeding due to low
platelet counts (platelets contribute to the clotting process). Plasma is extracted
from whole blood for use as volume expanders in the circulatory system, and in
some more advanced procedures, certain coagulation factors may be separated
from the plasma. There are also large regional storage facilities throughout the
United States and the world that are able to store cord blood stem cells for the
several decades that they would remain viable, although many hospital blood
banks have the capability for washing and glycerinating the cells before shipping
them to a storage facility.
Blood supplies are able to be maintained for longer periods than was true
a number of years ago, due to improved anticoagulants and nutrients added to
the unit to extend the life of the red blood cells (RBC). Although red blood cells
have a life span of around 100 to 120 days, the units are only good for approximately
1 month or slightly longer. This is because of the death of a percentage
of the RBCs each day leaves components in the unit that would be dangerous to
the patient receiving the blood. Under certain conditions, particularly for newborns,
Pedi-Paks are used to provide fresh blood for exchange transfusions when
a fetus has received antibodies against its own blood type, as occurs with Rh
incompatibilities between mother and fetus. Another function of blood banks
and some specialty storage centers is that of storing cord blood from newborns
and having it available for stem cell transplants when certain disease strike, such
as one of the various types of leukemia.
Many technologists and even some medical laboratory technicians find
employment in blood banks and become specialists in certain procedures that
are highly sophisticated. Testing personnel are also needed in the medical laboratory
to test blood for syphilis, hepatitis, and HIV. Most technologists and technicians
are used in hospital blood banks. The basic tests performed, even on blood
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