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This red liquid is living tissue that carries oxygen
and nutrients to all parts of the body, and carries carbon dioxide
and other waste products back to the lungs, kidneys and liver for
disposal. It fights against infection and helps heal wounds, so
we can stay healthy.
There's no substitute for blood. If people lose
blood from surgery or injury or if their bodies can't produce enough,
there is only one place to turn - volunteer blood donors.
Blood
may be transfused as whole blood or as one of its components. Because
patients seldom require all of the components of whole
blood, it makes sense to transfuse only that portion needed by
the patient for a specific condition or disease. This treatment,
referred to as “blood component therapy,” allows several
patients to benefit from one unit of donated whole blood. Blood
components include red blood cells, plasma, platelets, and cryoprecipitated
antihemophilic factor (AHF). Up to four components may be derived
from one unit of blood.
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If blood is treated to prevent
clotting and permitted to stand in a container, the red
blood cells, weighing the most, will settle to the bottom;
the plasma will stay on top; and the white blood cells
and platelets will remain suspended between the plasma
and the red blood cells. A centrifuge may be used to hasten
this separation process. The platelet-rich plasma is then
removed and placed into a sterile bag, and it can be used
to prepare platelets and plasma or cryoprecipitated AHF.
To make platelets, the platelet-rich plasma is centrifuged,
causing the platelets to settle at the bottom of the bag.
Plasma and platelets are then separated and made available
for transfusion. The plasma may also be pooled with plasma
from other donors and further processed, or fractionated,
to provide purified plasma proteins such as albumin, immunoglobulin
(IVIG) and clotting factors. |
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are perhaps the most recognizable component of whole
blood. Red blood cells contain hemoglobin, a complex iron-containing
protein that carries oxygen throughout the body and gives blood
its red color. The percentage of blood volume composed of red
blood cells is called the “hematocrit.” The average
hematocrit in an adult male is 47 percent; the average hematocrit
in adult females is 42 percent. There are about one billion red
blood cells in two to three drops of blood, and, for every 600
red blood cells, there are about 40 platelets and one white cell.
Manufactured in the bone marrow, red blood cells are continuously
being produced and broken down. They live for approximately 120
days in the circulatory system and are eventually removed by
the spleen.
Red blood cells are prepared from whole blood
by removing the plasma, or the liquid portion of the blood. They
can raise the patient's hematocrit and hemoglobin levels while
minimizing an increase in volume.
Patients who benefit most from
transfusions of red blood cells include those with chronic anemia
resulting
from disorders such as kidney failure, malignancies, or gastrointestinal
bleeding and those with acute blood loss resulting from trauma
or surgery. Since red blood cells have reduced amounts of plasma,
they are well suited for treating anemia patients who would not
tolerate the increased volume provided by whole blood, such as
patients with congestive heart failure or those who are elderly
or debilitated. Improvements in cell preservative solutions
over the last 15 years have increased the shelf life of red blood
cells from 21 to 42 days. Red blood cells may be treated and
frozen for extended storage (up to 10 years).
are responsible
for protecting the body from invasion by foreign substances such
as
bacteria,
fungi, and viruses. The majority of white blood cells are produced
in the bone marrow, where they outnumber red blood cells by two
to one. However, in the blood stream, there are about 600 red blood
cells for every white blood cell. There are several types of white
blood cells; Granulocytes and macrophages protect against infection
by surrounding and destroying invading bacteria and viruses, and
lymphocytes aid in the immune defense.
(or thrombocytes) are very small cellular components of blood that
help the clotting process by
sticking to the lining of blood vessels. Platelets are made in
the bone marrow and survive in the circulatory system for an average
of 9-10 days before being removed from the body by the spleen.
The platelet is vital to life, because it helps prevent both massive
blood-loss resulting from trauma and blood vessel leakage that
would otherwise occur in the course of normal, day-to-day activity.
Units of platelets are prepared by using a centrifuge to separate
the platelet-rich plasma from the donated unit of whole blood.
The platelet-rich plasma is then centrifuged again to concentrate
the platelets further.
Platelets may also be obtained from a donor
by a process known as apheresis,
or plateletpheresis. In this process, blood is drawn from the donor
into an apheresis
instrument, which, using centrifugation, separates the blood into
its components, retains the platelets, and returns the remainder
of the blood to the donor. The resulting component contains about
six times as many platelets as a unit of platelets obtained from
whole blood. Platelets are used to treat a condition called thrombocytopenia,
in which there is a shortage of platelets, and in patients with
abnormal platelet function. Platelets are stored at room temperature
for up to five days.
is the liquid portion of the blood — a
protein-salt solution in which red and white blood cells and platelets
are suspended. Plasma, which is 90 percent water, constitutes about
55 percent of blood volume. Plasma contains albumin (the chief
protein constituent), fibrinogen (responsible, in part, for the
clotting of blood), globulins (including antibodies), and other
clotting proteins. Plasma serves a variety of functions, from maintaining
a satisfactory blood pressure and volume to supplying critical
proteins for blood clotting and immunity. It also serves as the
medium of exchange for vital minerals such as sodium and potassium,
thus helping maintain a proper balance in the body, which is critical
to cell function. Plasma is obtained by separating the liquid portion
of blood from the cells. Plasma is usually not used for transfusion
purpose but is fractionated (separated) into specific products
such as albumin, specific clotting factor concentrates and IVIG
(intravenous immune globulin).
is plasma frozen within
hours after donation to preserve clotting factors, stored for one
to seven years, and thawed before it is transfused. It is most
often used to treat certain bleeding disorders when a clotting
factor or multiple factors are deficient and no factor-specific
concentrate is available. It can also be used for plasma replacement
via a process called plasma exchange.
is the portion of plasma
that is rich in certain clotting factors, including Factor VIII,
fibrinogen, von Willebrand factor and Factor XIII. Cryoprecipitated
AHF is removed from plasma by freezing and then slowly thawing
the plasma. It is used to prevent or control bleeding in individuals
with hemophilia and von Willebrand’s disease, which are common,
inherited major coagulation abnormalities. Its use in these conditions
is reserved for times when viral-inactivated concentrates containing
Factor VIII and von Willebrand factor are unavailable and plasma
components must be used. It may also be used as hemostatic preparation
[fibrin sealant or fibrin glue] in surgery.
are
concentrates of specific plasma proteins that are prepared from
pools (many units) of plasma.
Plasma derivatives are obtained through a process, known as fractionation,
developed during World War II, and are heat-treated and/or solvent
detergent- treated to kill certain viruses, including HIV and hepatitis
B and C.
Plasma derivatives include:
- Factor VIII Concentrate
- Factor IX Concentrate
- Anti-Inhibitor Coagulation
Complex (AICC)
- Albumin
- Immune Globulins, including Rh Immune
Globulin
- Anti-Thrombin III Concentrate
- Alpha 1-Proteinase
Inhibitor Concentrate
can be collected by apheresis
or by centrifugation of whole blood. They are transfused within
24 hours after collection
and are used for infections that are unresponsive to antibiotic
therapy. The effectiveness of white blood cell transfusion is still
being investigated. |