Signals and indicators – Indicators
Reexamination Certificate
2000-02-03
2002-04-02
Hirshfeld, Andrew H. (Department: 2859)
Signals and indicators
Indicators
C116S201000, C040S299010
Reexamination Certificate
active
06363878
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
A key type identification system for blood products.
2. Description of the Relevant Art
Human blood is “Typed,” or classified into groups, to determine its compatibility with blood or blood products from another individual. If incompatible blood or blood products are administered (as with a blood transfusion), the automatic blood cell- and tissue-destroying process which ensues can be disastrous, and potentially fatal to the recipient.
The current blood typing system is extremely sophisticated and complex, to the point that it can be difficult even for experienced health care professionals to comprehend or remember. Therefore, health care institutions engaged in the practice of transfusion medicine almost always utilize “Blood Banks,” or departments devoted exclusively to the maintenance, processing, typing, distribution, and documentation of all aspects of transfusion therapy.
While the compartmentalization of the blood bank is essential for safety and quality assurance, it often hides the technical aspects of transfusion therapy from health care personnel who are not directly involved with the Blood Bank. Although errors inevitably occur in blood processing, they are usually identified and corrected before the blood is administered. Nonetheless, the health care profession must continue to seek better safeguards and methods of avoiding the potentially fatal administration of incompatible blood products to a patient.
The current ABO typing system is complex and errors can occur anywhere in the processing of blood or blood products.
There are two parts or components of human blood which blood typing is based: the Red Blood Cells (RBC's), and the Plasma. Red blood cells primarily carry oxygen to the tissues, and Plasma is the liquid medium through which they travel throughout the body.
On the surface of each RBC are “Antigens,” or proteins, which can react with “Antibodies,” found in the plasma. These Antigen-Antibody reactions usually result in the destruction of the RBC's, and this process is an extension of one of the body's natural methods of self defense. Blood “Typing” is a process which identifies the common or major Antigens and Antibodies found in blood. The three antigens are named “A,” “B,” an “RH”; the antibodies and are named for the antigens with which they combine: “Anti-A”, “Anti-B”, and “Anti-RH.” Antigens are found on RBC's, and Antibodies are fo und in Plasma.
TABLE A
MAJOR ANTIGENS ON RBC'S
MAJOR ANTIBODIES IN PLASMA
A
Anti-A
B
Anti-B
Neither A nor B
—
RH
Anti-RH
When an antigen is combined with its corresponding Antibody, i.e., A with Anti-A, B with Anti-B, or RH with Anti-RH, a series of chemical reactions occur which ultimately destroy the RBC, and may trigger other tissue damaging processes. Humans have developed such that the genetically determined presence or absence of Antigens A, B, and RH determines the corresponding presence or absence of Anti-A, Anti-B, and Anti-RH.
In normal individuals, if A is found on the surface of the RBC, the plasma does not contain Anti-A; if A is not present on the surface of the RBC, the plasma does contain Anti-A. The same applies for B and RH. If both A and B are found on the surface, then neither Anti-A nor Anti-B are present in the plasma. If neither A nor B are present on the surface of the RBC, then both Anti-A and Anti-B are found in the plasma. The following Table B summarizes.
TABLE B
ANTIGEN
ANTIBODIES
PRESENCE
RH ANTIGEN
PRESENT
ON RBC
PRESENCE ON RBC
BLOOD TYPE
IN PLASMA
A Only
Not Present
A Negative
Anti-B, Anti-RH
A Only
Present
A Positive
Anti-B
B Only
Not Present
B Negative
Anti-A, Anti-RH
B Only
Present
B Positive
Anti-A
A and B
Not Present
AB Negative
Anti-RH
A and B
Present
AB Positive
None
Neither
Not Present
O Negative
Anti-A, Anti-B,
Anti-RH
Neither
Present
O Positive
Anti-A Anti-B
There are, by definition, combinations of blood types which will unite the antigen with its corresponding antibody, triggering the destruction of the RBC. For example, whole blood of type A positive (with RBC surface antigens A and RH, and plasma antibody Anti-B) when mixed with whole blood of type B positive (with RBC surface antigens B and RH and plasma antibody Anti-A) will bring together the RBC- destroying combinations of surface antigen A with plasma antibody Anti-A and surface antigen B with plasma antibody Anti-B. Thus, these types are considered “incompatible.”
A patient can only receive whole blood of the exact same type. This is called “type specificity.” Because this limits the quantity of blood that is available to any given patient for transfusion therapy, whole blood collected from blood donors is usually fractionated or separated into its components to yield plasma, platelets and packed RBC's.
The ABO typing system is also used to classify these individually separated blood components (i.e., Fresh Frozen Plasma, Platelets, and Packed RBC's). The same compatibility rules apply, but the presence or absence of RBC's (and their surface antigens) or plasma (and its antibodies) in the blood component determines its compatibility with a patient's whole-blood. Packed RBC's typically do not contain Plasma; therefore, the absence of plasma antibodies increases the number of combinations of blood types with which the Packed RBC's are compatible.
A patient having blood type A positive, for example, while able to receive only whole blood of type A positive, could also receive Packed RBC's of types A positive, A negative, O positive and O negative, and Plasma of types A positive and AB positive. Similarly, a patient of blood type B negative, while able to receive only whole blood of type B negative, could also receive Packed RBC's of types B negative and O negative; and Plasma of types B negative, B positive, AB negative and AB positive. The following table summarizes whole blood types and their compatibility with individual blood components.
TABLE C
A
A
B
B
AB
AB
O
O
NEG
POS
NEG
POS
NEG
POS
NEG
POS
Compatibility Between Whole Blood Type (Vertical) and Packed RBC
Type (Horizontal)
A NEG
X
X
A POS
X
X
X
X
B NEG
X
X
B POS
X
X
X
X
AB NEG
X
X
X
X
AB POS
X
X
X
X
X
X
X
X
O NEG
X
O POS
X
X
Compatibility Between Whole Blood Type (Vertical) and
Plasma Type (Horizontal)
A NEG
X
X
X
X
A POS
X
X
B NEG
X
X
X
X
B POS
X
X
AB NEG
X
X
AB POS
X
X
O NEG
X
X
X
X
X
X
X
X
O POS
X
X
X
X
X indicates “Compatible”
It is the shared responsibility of the blood bank and the individual health care practitioners to know and remember which blood mixture combinations are compatible, and to recognize and remember those combinations which are incompatible (and potentially lethal).
With any process, errors occur unavoidably. There are many areas in transfusion medicine into which human error can be introduced. Although regulations require that quality control measures and error identification and analysis programs be ongoing in health care facilities, the complete elimination of errors in collection, typing, labeling, distribution, administration, and documentation, can never be achieved. All attempts, therefore, must be focused on the minimization of certain types of easily avoidable errors.
While many safeguards are in place for the prevention of this potential catastrophe, there are still situations in which inadvertent administrations occur. For example, a unit of blood may have been sent to a different patient with the same name; the blood administrator may have confused one patient's blood product for that of another patient. A wrong unit of blood may have been given under the stress of managing the patient's life-threatening emergency, or during the late-night shift, or at any time when the administrator's vigilance may be compromised.
Most patient-type and blood-product-type identification systems focus on the administrator's verification of the accuracy of labeled information to assure type compatibility. Some inventions have attempted to invoke technology such as portable computers and bar-code readers to ide
Hirshfeld Andrew H.
Samuels Gauthier & Stevens
Smith R. A.
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