Packed red blood cells
Encyclopedia
In transfusion medicine
, packed red blood cells are red blood cells that have been separated from whole blood
for transfusion purposes. The product is typically abbreviated RBC or PRBC, and sometimes LRBC for leukoreduced products. The name "Red Blood Cells" with initial capitals indicates a standardized product in the United States.
RBCs are used to restore oxygen carrying capacity to the blood of a patient that is suffering from anemia
due to trauma or other medical problems, and are one of the most important blood components used in transfusion medicine. Historically they were transfused as part of whole blood, but in modern practice the RBCs and plasma components are transfused separately. The process of identifying a compatible blood product for transfusion is complicated and giving incompatible RBCs to a patient can be fatal.
The RBCs are mixed with an anticoagulant
and usually a storage solution which provides nutrients and preserves the functionality of the living cells, which are stored at refrigerated temperatures. The cells are separated from the fluid portion of the blood either after it is collected from a donor
or during the collection process by apheresis
. The product is sometimes modified after collection to meet specific patient requirements.
by 3-4% and the blood hemoglobin
concentration by 1 g/dl.
The exact criteria for when a patient requires a transfusion are often set by a standards organization such as a hospital transfusion committee. Typical triggers for transfusion include low patient hemoglobin
test values and active severe bleeding. Because of the possible complications with RBCs and sometimes because of scarcity of donor blood components, other treatments are preferred for anemia when the patient's condition is not critical. Iron supplements and vitamins or erythropoietin
can be used to help the patient's body produce more red blood cells.
Donor RBCs must be compatible with the recipient to avoid potentially life-threatening reactions. Incompatible cells will be destroyed by the patient's immune system and the free hemoglobin released from the damaged cells is toxic, particularly to the kidneys. This is called a hemolytic transfusion reaction
, which is often immediately apparent during the transfusion but may also take several days to develop. Other complications of transfusion, such as allergic reactions or volume overload, can also be dangerous. Transfusion related acute lung injury
(TRALI) is not usually associated with RBCs, though cases have been reported.
and Rh
type, specifically the phenotype
, and the "screen" refers to testing for atypical antibodies that might cause transfusion problems. The typing and screening are also performed on donor blood. The blood groups represent antigens on the surface of the red blood cells which might react with antibodies in the recipient.
The ABO blood group system has four basic phenotypes: O, A, B, and AB. In the former Soviet Union
these were called I, II, III, and IV, respectively. There are two important antigens in the system: A and B. Red cells without A or B are called type O, and red cells with both are called AB. Except in unusual cases like infants or seriously immunocompromised individuals, all people will have antibodies to any ABO blood type that isn't present on their own red blood cells, and will have an immediate hemolytic reaction to a unit that is not compatible with their ABO type. In addition to the A and B antigens, there are rare variations which can further complicate transfusions, such as the Bombay phenotype.
The Rh blood group system consists of nearly around 50 different antigens, but the one of the greatest clinical interest is the "D" antigen, though it has other names and is commonly just called "negative" or "positive." Unlike the ABO antigens, a recipient will not usually react to the first incompatible transfusion because the adaptive immune system
does not immediately recognize it. After an incompatible transfusion the recipient may develop an antibody to the antigen and will react to any further incompatible transfusions. This antibody is important because it is the most frequent cause of hemolytic disease of the newborn
. Incompatible red blood cells are sometimes given to recipients who will never become pregnant, such as males or postmenopausal women, as long as they do not have an antibody, since the greatest risk of Rh incompatible blood is to current or future pregnancies.
For RBCs, type O negative blood is considered a "universal donor" as recipients with types A, B, or AB can almost always receive O negative blood safely. Type AB positive is considered a "universal recipient" because they can receive the other ABO/Rh types safely. These are not truly universal, as other red cell antigens can further complicate transfusions.
There are many other human blood group systems
and most of them are only rarely associated with transfusion problems. A screening test is used to identify if the recipient has any antibodies to any of these other blood group systems. If the screening test is positive, a complex set of tests must follow to identify which antibody the recipient has by process of elimination. Finding suitable blood for transfusion when a recipient has multiple antibodies or antibodies to extremely common antigens can be very difficult and time consuming.
Because this testing can take time, doctors will sometimes order a unit of blood transfused before it can be completed if the recipient is in critical condition. Typically two to four units of O negative blood are used in these situations, since they are unlikely to cause a reaction. A potentially fatal reaction is possible if the recipient has pre-existing antibodies, and uncrossmatched blood is only used in dire circumstances. Since O negative blood is not common, other blood types may be used if the situation is desperate.
and is spun in a centrifuge. The red blood cells are denser and settle to the bottom, and the majority of the liquid blood plasma
remains on the top. The plasma is separated and the red blood cells are kept with a minimal amount of fluid. Generally an additive solution of citrate, dextrose, and adenine is mixed with the cells to keep them alive during storage. This process is sometimes done as automated apheresis
where the centrifuging and mixing take place at the donation site.
Red Blood Cells are sometimes modified to address specific patient needs. The most common modification is leukoreduction, where the donor blood is filtered to remove white cells. The blood may also be irradiated, which destroys the DNA
in the white cells and prevents graft versus host disease
, which may happen if the blood donor and recipient are closely related. Other modifications, such as washing the RBCs to remove any remaining plasma, are much less common.
With additive solutions, RBCs are typically kept at refrigerated temperatures for up to 42 days. In some patients, use of RBCs that are much fresher is important. With the addition of glycerol or other cryoprotectants, RBCs can be frozen for much longer. Frozen RBCs are typically assigned a ten year expiration date, though older units have been transfused successfully. The freezing process is expensive and time-consuming and is generally reserved for rare units such as ones that can be used in patients that have unusual antibodies.
Transfusion medicine
Transfusion medicine is the branch of medicine that is concerned with the transfusion of blood and blood components. The blood bank is the section of the clinical laboratory where medical technologists process and distribute blood products under the supervision of a medical director, often...
, packed red blood cells are red blood cells that have been separated from whole blood
Whole blood
Whole blood is a term used in transfusion medicine for human blood from a standard blood donation. The blood is typically combined with an anticoagulant during the collection process, but is generally otherwise unprocessed...
for transfusion purposes. The product is typically abbreviated RBC or PRBC, and sometimes LRBC for leukoreduced products. The name "Red Blood Cells" with initial capitals indicates a standardized product in the United States.
RBCs are used to restore oxygen carrying capacity to the blood of a patient that is suffering from anemia
Anemia
Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...
due to trauma or other medical problems, and are one of the most important blood components used in transfusion medicine. Historically they were transfused as part of whole blood, but in modern practice the RBCs and plasma components are transfused separately. The process of identifying a compatible blood product for transfusion is complicated and giving incompatible RBCs to a patient can be fatal.
The RBCs are mixed with an anticoagulant
Anticoagulant
An anticoagulant is a substance that prevents coagulation of blood. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some anticoagulants are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis...
and usually a storage solution which provides nutrients and preserves the functionality of the living cells, which are stored at refrigerated temperatures. The cells are separated from the fluid portion of the blood either after it is collected from a donor
Blood donation
A blood donation occurs when a person voluntarily has blood drawn and used for transfusions or made into medications by a process called fractionation....
or during the collection process by apheresis
Apheresis
Apheresis is a medical technology in which the blood of a donor or patient is passed through an apparatus that separates out one particular constituent and returns the remainder to the circulation...
. The product is sometimes modified after collection to meet specific patient requirements.
Clinical aspects
Red blood cells are the component of blood that carry oxygen from the lungs to the rest of the body. If the body does not have enough red blood cells, due to blood loss, anemia, or other medical conditions, then RBCs are transfused to improve the oxygen carrying capacity. RBCs are also used in exchange transfusions where the patient's abnormal cells are replaced with healthy donor cells. One unit of PRBCs typically will raise the hematocritHematocrit
The hematocrit or packed cell volume or erythrocyte volume fraction is the percentage of the concentration of red blood cells in blood. It is normally about 45% for men and 40% for women...
by 3-4% and the blood hemoglobin
Hemoglobin
Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...
concentration by 1 g/dl.
The exact criteria for when a patient requires a transfusion are often set by a standards organization such as a hospital transfusion committee. Typical triggers for transfusion include low patient hemoglobin
Hemoglobin
Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...
test values and active severe bleeding. Because of the possible complications with RBCs and sometimes because of scarcity of donor blood components, other treatments are preferred for anemia when the patient's condition is not critical. Iron supplements and vitamins or erythropoietin
Erythropoietin
Erythropoietin, or its alternatives erythropoetin or erthropoyetin or EPO, is a glycoprotein hormone that controls erythropoiesis, or red blood cell production...
can be used to help the patient's body produce more red blood cells.
Donor RBCs must be compatible with the recipient to avoid potentially life-threatening reactions. Incompatible cells will be destroyed by the patient's immune system and the free hemoglobin released from the damaged cells is toxic, particularly to the kidneys. This is called a hemolytic transfusion reaction
Hemolytic transfusion reaction
An acute hemolytic transfusion reaction is a type of transfusion reaction that is associated with hemolysis.It occurs very soon after the transfusion. It can occur quickly upon transfusing a few milliliters, or up to 1-2 hours post-transfusion...
, which is often immediately apparent during the transfusion but may also take several days to develop. Other complications of transfusion, such as allergic reactions or volume overload, can also be dangerous. Transfusion related acute lung injury
Transfusion related acute lung injury
In medicine, transfusion related acute lung injury is a serious blood transfusion complication characterized by the acute onset of non-cardiogenic pulmonary edema following transfusion of blood products....
(TRALI) is not usually associated with RBCs, though cases have been reported.
Compatibility testing
To avoid transfusion reactions, the donor and recipient blood are tested, typically ordered as a "type and screen" for the recipient. The "type" in this case is the ABOABO blood group system
The ABO blood group system is the most important blood type system in human blood transfusion. The associated anti-A antibodies and anti-B antibodies are usually IgM antibodies, which are usually produced in the first years of life by sensitization to environmental substances such as food,...
and Rh
Rh blood group system
The Rh blood group system is one of thirty current human blood group systems. Clinically, it is the most important blood group system after ABO. At Present, the Rh blood group system consists of 50 defined blood-group antigens, among which the 5 antigens D, C, c, E, and e are the most important...
type, specifically the phenotype
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...
, and the "screen" refers to testing for atypical antibodies that might cause transfusion problems. The typing and screening are also performed on donor blood. The blood groups represent antigens on the surface of the red blood cells which might react with antibodies in the recipient.
The ABO blood group system has four basic phenotypes: O, A, B, and AB. In the former Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
these were called I, II, III, and IV, respectively. There are two important antigens in the system: A and B. Red cells without A or B are called type O, and red cells with both are called AB. Except in unusual cases like infants or seriously immunocompromised individuals, all people will have antibodies to any ABO blood type that isn't present on their own red blood cells, and will have an immediate hemolytic reaction to a unit that is not compatible with their ABO type. In addition to the A and B antigens, there are rare variations which can further complicate transfusions, such as the Bombay phenotype.
The Rh blood group system consists of nearly around 50 different antigens, but the one of the greatest clinical interest is the "D" antigen, though it has other names and is commonly just called "negative" or "positive." Unlike the ABO antigens, a recipient will not usually react to the first incompatible transfusion because the adaptive immune system
Adaptive immune system
The adaptive immune system is composed of highly specialized, systemic cells and processes that eliminate or prevent pathogenic growth. Thought to have arisen in the first jawed vertebrates, the adaptive or "specific" immune system is activated by the “non-specific” and evolutionarily older innate...
does not immediately recognize it. After an incompatible transfusion the recipient may develop an antibody to the antigen and will react to any further incompatible transfusions. This antibody is important because it is the most frequent cause of hemolytic disease of the newborn
Hemolytic disease of the newborn
Hemolytic disease of the newborn, also known as hemolytic disease of the fetus and newborn, HDN, HDFN, or erythroblastosis fetalis, is an alloimmune condition that develops in a fetus, when the IgG molecules produced by the mother pass through the placenta...
. Incompatible red blood cells are sometimes given to recipients who will never become pregnant, such as males or postmenopausal women, as long as they do not have an antibody, since the greatest risk of Rh incompatible blood is to current or future pregnancies.
For RBCs, type O negative blood is considered a "universal donor" as recipients with types A, B, or AB can almost always receive O negative blood safely. Type AB positive is considered a "universal recipient" because they can receive the other ABO/Rh types safely. These are not truly universal, as other red cell antigens can further complicate transfusions.
There are many other human blood group systems
Human blood group systems
The International Society of Blood Transfusion currently recognises 30 major blood group systems . Thus, in addition to the ABO antigens and Rhesus antigens, many other antigens are expressed on the red blood cell surface membrane...
and most of them are only rarely associated with transfusion problems. A screening test is used to identify if the recipient has any antibodies to any of these other blood group systems. If the screening test is positive, a complex set of tests must follow to identify which antibody the recipient has by process of elimination. Finding suitable blood for transfusion when a recipient has multiple antibodies or antibodies to extremely common antigens can be very difficult and time consuming.
Because this testing can take time, doctors will sometimes order a unit of blood transfused before it can be completed if the recipient is in critical condition. Typically two to four units of O negative blood are used in these situations, since they are unlikely to cause a reaction. A potentially fatal reaction is possible if the recipient has pre-existing antibodies, and uncrossmatched blood is only used in dire circumstances. Since O negative blood is not common, other blood types may be used if the situation is desperate.
Collection and processing
Most frequently, whole blood is collected from a blood donationBlood donation
A blood donation occurs when a person voluntarily has blood drawn and used for transfusions or made into medications by a process called fractionation....
and is spun in a centrifuge. The red blood cells are denser and settle to the bottom, and the majority of the liquid blood plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
remains on the top. The plasma is separated and the red blood cells are kept with a minimal amount of fluid. Generally an additive solution of citrate, dextrose, and adenine is mixed with the cells to keep them alive during storage. This process is sometimes done as automated apheresis
Apheresis
Apheresis is a medical technology in which the blood of a donor or patient is passed through an apparatus that separates out one particular constituent and returns the remainder to the circulation...
where the centrifuging and mixing take place at the donation site.
Red Blood Cells are sometimes modified to address specific patient needs. The most common modification is leukoreduction, where the donor blood is filtered to remove white cells. The blood may also be irradiated, which destroys the DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
in the white cells and prevents graft versus host disease
Transfusion-associated graft versus host disease
Transfusion-associated graft versus host disease is a rare complication of blood transfusion, in which the donor T lymphocytes mount an immune response against the recipient's lymphoid tissue. Donor lymphocytes are usually identified as foreign and destroyed by the recipient's immune system...
, which may happen if the blood donor and recipient are closely related. Other modifications, such as washing the RBCs to remove any remaining plasma, are much less common.
With additive solutions, RBCs are typically kept at refrigerated temperatures for up to 42 days. In some patients, use of RBCs that are much fresher is important. With the addition of glycerol or other cryoprotectants, RBCs can be frozen for much longer. Frozen RBCs are typically assigned a ten year expiration date, though older units have been transfused successfully. The freezing process is expensive and time-consuming and is generally reserved for rare units such as ones that can be used in patients that have unusual antibodies.