Biomedical Engineering Reference
In-Depth Information
Box 14.5
Whole blood
Whole blood is blood that has been aseptically withdrawn from humans. A suitable anticoagu-
lant is added (often heparin or a citrate-dextrose-based substance), although no preservative
is present. The blood is usually stored at temperatures ranging from 1-8
C, and has a short
shelf life (48 h after collection if heparin is used as the anticoagulant, or up to 35 days if
citrate-phosphate-dextrose with adenine is employed).
The blood is generally warmed to 37
C immediately prior to transfusion. Whole blood is of-
ten used to replace blood lost due to injury or surgery. The number of units (one unit equals ap-
proximately 510 ml) administered depends upon the health and age of the recipient, along with
the therapeutic indication. Administration of whole blood may also be undertaken to supply a
recipient with a particular blood constituent (e.g. a clotting factor, immunoglobulin, platelets or
red blood cells). However, this practice is minimized, in favour of direct administration of the
specifi c blood constituent needed.
Associated with the administration of blood or blood products is the risk of accidental trans-
mission of infectious agents such as hepatitis viruses or HIV. The prevention of accidental
pathogen transmission relies upon:
•
careful screening of all blood donors/donations;
•
introduction of methods of pathogen removal/inactivation during the processing steps;
•
careful screening of all fi nished products.
The identity of each blood donor should be recorded, and all donor blood bags must be
labelled carefully. Traceability of individual blood donors/donations is essential, in case the
donor or product is subsequently found to harbour blood-borne pathogens. The risk of contami-
nation of blood during collection/processing is minimized by using closed systems and strict
aseptic technique.
Before any blood donation is released for issue/processing, it must be tested for the presence
of various pathogens particularly likely to be present in blood. In most countries, these tests
include immunoassays capable of detecting:
•
hepatitis B surface antigen (HBsAg);
•
antibodies to HIV;
•
antibodies to hepatitis C virus;
•
syphilis antibodies.
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