Blood
donation
From Wikipedia, the free encyclopedia
A blood donation occurs when
a person voluntarily has blood drawn and used for transfusions
and/or made into biopharmaceutical medications by a process called fractionation (separation of whole-blood components). Donation may be of
whole-blood (WB), or of specific components directly (the latter called
apheresis). Blood banks often participate in the collection process as well as the
procedures that follow it.
In the developed world, most blood
donors are unpaid volunteers (voluntary non remunerated repeat donations, VNRD)
who donate blood for a community supply. In poorer countries, established
supplies are limited and donors usually give blood when family or friends need
a transfusion (directed donation). Many donors donate as an act of charity, but
some are paid and in some cases there are incentives other than money such as paid time off
from work. Donors can also have blood drawn for their own future use
(autologous donation). Donating is relatively safe, but some donors have
bruising where the needle is inserted or may feel faint.
Potential donors are evaluated for
anything that might make their blood unsafe to use. The screening includes
testing for diseases that can be transmitted by a blood transfusion, including HIV and viral hepatitis.
The donor must also answer questions about medical history
and take a short physical examination to make sure the donation is not hazardous to his or her
health. How often a donor can give varies from days to months based on what he
or she donates and the laws of the country where the donation takes place. For
example in the United States, donors must wait eight weeks (56 days) between whole blood donations but only three days between platelet pheresis donations.[1]
The amount of blood drawn and the
methods vary. The collection can be done manually or with automated equipment
that only takes specific portions of the blood. Most of the components of blood
used for transfusions have a short shelf life,
and maintaining a constant supply is a persistent problem. This has led to some
increased interest in autotransfusion,
whereby a patient's blood is salvaged during surgery for continuous reinfusion
- or alternatively, is "self-donated" prior to when it will be
needed. (Generally the notion of "donation" does not refer to giving
to one's self, though in this context it has become somewhat acceptably
idiomatic.)
Types
of donation
Blood donations are divided into
groups based on who will receive the collected blood.[2]
An 'allogeneic' (also called 'homologous') donation is when a donor gives blood
for storage at a blood bank for transfusion
to an unknown recipient. A 'directed' donation is when a person, often a family
member, donates blood for transfusion
to a specific individual.[3]
Directed donations are relatively rare when an established supply exists.[4]
A 'replacement donor' donation is a hybrid of the two and is common in
developing countries such as Ghana.[5]
In this case, a friend or family member of the recipient donates blood to
replace the stored blood used in a transfusion, ensuring a consistent supply.
When a person has blood stored that will be transfused back to the donor at a
later date, usually after surgery, that is called an 'autologous'
donation.[6]
Blood that is used to make medications can be made from allogeneic donations or
from donations exclusively used for manufacturing.[7]
Blood is sometimes collected using
similar methods for therapeutic
phlebotomy, similar to the ancient practice of
bloodletting,
which is used to treat conditions such as hereditary
hemochromatosis or polycythemia vera.
This blood is sometimes treated as a blood donation, but may be immediately
discarded if it cannot be used for transfusion or further manufacturing.
The actual process varies according
to the laws of the country, and recommendations to donors vary according to the
collecting organization.[8][9][10]
The World
Health Organization gives recommendations for blood
donation policies,[11]
but in developing countries many of these are not followed. For example, the
recommended testing requires laboratory facilities, trained staff, and
specialized reagents, all of which may not be available or too expensive in
developing countries.[12]
An event where donors come to donate
allogeneic blood is sometimes called a 'blood drive'
or a 'blood donor session'. These can occur at a blood bank, but they are often
set up at a location in the community such as a shopping center, workplace,
school, or house of worship.[13]
Screening
Donors are typically required to
give consent for the process and this requirement means minors cannot
donate without permission from a parent or guardian.[14]
In some countries, answers are associated with the donor's blood, but not name,
to provide anonymity; in others, such as the United States, names are kept to
create lists of ineligible donors.[15]
If a potential donor does not meet these criteria, they are 'deferred'. This
term is used because many donors who are ineligible may be allowed to donate
later. Blood banks in the United States may be required to label the blood if
it is from a therapeutic donor, so some do not accept donations from donors
with any blood disease.[16]
Others, such as the Australian
Red Cross Blood Service, accept
blood from donors with hemochromatosis.
It is a genetic disorder that does not affect the safety of the blood.[17]
All blood donors are asked questions
about their medical history.
The donor's race or ethnic
background is sometimes important since certain blood
types, especially rare ones, are more
common in certain ethnic groups.[18]
Historically, donors were segregated or excluded on race, religion, or
ethnicity, but this is no longer a standard practice.[19]
Recipient
safety
Donors are screened for health risks
that could make the donation unsafe for the recipient. Some of these
restrictions are controversial, such as restricting donations from MSMs (men
who have sex with men) for HIV risk.[20]
In 2011, the UK reduced its blanket ban on MSM donors to a narrower restriction
which only prevents MSMs from donating blood if they have had sex with other men
within the past year. Canada continued its ban. US senator John Kerry
was pushing for the end to the 28-year-old ban in the US.[21]
Autologous
donors are not always screened for recipient safety problems since the donor is
the only person who will receive the blood.[22]
Donors are also asked about medications such as dutasteride,
since they can be dangerous to a pregnant woman receiving the blood.[23]
Donors are examined for signs and symptoms of
diseases that can be transmitted in a blood transfusion,
such as HIV, malaria, and viral hepatitis.
Screening may include questions about risk factors
for various diseases, such as travel to countries at risk for malaria or variant
Creutzfeldt-Jakob Disease (vCJD).
These questions vary from country to country. For example, while blood centers
in Québec, Poland, and many other places defer donors who lived in the United Kingdom
for risk of vCJD,[24][25]
donors in the United Kingdom are only restricted for vCJD risk if they have had
a blood transfusion in the United Kingdom.[26]
Donor
safety
The donor is also examined and asked
specific questions about their medical history to make sure that donating blood
is not hazardous to their health. The donor's hematocrit
or hemoglobin
level is tested to make sure that the loss of blood will not make them anemic, and this check is the most common reason that a donor is
ineligible.[27]
Pulse, blood pressure,
and body temperature are also evaluated. Elderly donors are sometimes also
deferred on age alone because of health concerns.[28]
The safety of donating blood during pregnancy has not been studied thoroughly,
and pregnant women are usually deferred.[29]
Blood
testing
The donor's blood type
must be determined if the blood will be used for transfusions. The collecting
agency usually identifies whether the blood is type A, B, AB, or O and the donor's Rh (D)
type and will screen for antibodies
to less common antigens. More testing, including a crossmatch,
is usually done before a transfusion. Group O is often cited as the
"universal donor"[30]
but this only refers to red cell
transfusions. For plasma transfusions the system is reversed and AB is the universal
donor type.[31]
Most blood is tested for diseases,
including some STDs.[32]
The tests used are high-sensitivity screening tests and no actual diagnosis is made. Some of the test results
are later found to be false positives using more specific testing.[33]
False negatives are rare, but donors are discouraged from using blood
donation for the purpose of anonymous STD screening because a false negative could mean a contaminated unit.
The blood is usually discarded if these tests are positive, but there are some
exceptions, such as autologous donations. The donor is generally notified of the test
result.[34]
Donated blood is tested by many
methods, but the core tests recommended by the World Health Organization are
these four:
- Hepatitis B
Surface Antigen
- Antibody to Hepatitis C
- Antibody to HIV, usually subtypes 1 and 2
- Serologic test for Syphilis
The WHO reported in 2006 that 56 out
of 124 countries surveyed did not use these basic tests on all blood donations.[12]
A variety of other tests for transfusion
transmitted infections are often
used based on local requirements. Additional testing is expensive, and in some
cases the tests are not implemented because of the cost.[35]
These additional tests include other infectious diseases such as West Nile Virus.[36]
Sometimes multiple tests are used for a single disease to cover the limitations
of each test. For example, the HIV antibody test will not
detect a recently infected donor, so some blood banks use a p24 antigen
or HIV nucleic acid test in addition to the basic antibody test to detect
infected donors during that period. Cytomegalovirus
is a special case in donor testing in that many donors will test positive for
it.[37]
The virus is not a hazard to a healthy recipient, but it can harm infants[38]
and other recipients with weak immune systems.[37]
Obtaining
the blood
There are two main methods of
obtaining blood from a donor. The most frequent is to simply take the blood from
a vein as whole blood. This blood is typically separated into parts, usually red blood cells
and plasma, since most recipients need only a specific component for
transfusions. A typical donation is 450 millilitres (or approximately one US
pint)[39]
of whole blood,
though 500 millilitre donations are also common. Historically, blood donors in India would donate only 250 or 350 millilitre and donors in the People's
Republic of China would donate only 200 millilitres,
though larger 300 and 400 millilitre donations have become more common.[40]
The other method is to draw blood
from the donor, separate it using a centrifuge
or a filter, store the desired part, and return the rest to the donor. This
process is called apheresis, and it is often done with a machine specifically designed
for this purpose. This process is especially common for plasma and platelets.
For direct transfusions
a vein can be used but the blood may be taken from an artery instead.[41]
In this case, the blood is not stored, but is pumped directly from the donor
into the recipient. This was an early method for blood transfusion and is
rarely used in modern practice.[42]
It was phased out during World War II
because of problems with logistics, and doctors returning from treating wounded soldiers set
up banks for stored blood when they returned to civilian life.[43]
Site
preparation and drawing blood
The blood is drawn from a large arm vein close to the skin,
usually the median cubital vein on the inside of the elbow. The skin over the blood vessel
is cleaned with an antiseptic such as iodine or chlorhexidine[44]
to prevent skin bacteria from contaminating the collected blood[44]
and also to prevent infections where the needle pierced the donor's skin.[45]
A large[46]
needle (16 to 17 gauge) is used to minimize shearing forces that may physically damage red blood
cells as they flow through the needle.[47]
A tourniquet
is sometimes wrapped around the upper arm to increase the pressure of the blood in the arm
veins and speed up the process. The donor
may also be prompted to hold an object and squeeze it repeatedly to increase the blood flow through the vein.
Whole
blood
The most common method is collecting
the blood from the donor's vein into a container. The amount of blood drawn
varies from 200 milliliters to 550 milliliters depending on the country, but
450-500 milliliters is typical.[37]
The blood is usually stored in a flexible plastic bag that also contains sodium citrate,
phosphate,
dextrose, and
sometimes adenine. This
combination keeps the blood from clotting and preserves it during storage.[48]
Other chemicals are sometimes added during processing.
The plasma from whole blood can be
used to make plasma for transfusions or it can also be processed into other medications using a
process called fractionation. This was a development of the dried plasma used to treat the wounded during World War II
and variants on the process are still used to make a variety of other medications.[49]
[50]
Apheresis
Apheresis is a blood donation method
where the blood is passed through an apparatus that separates out one
particular constituent and returns the remainder to the donor. Usually the
component returned is the red blood cells, the portion of the blood that takes
the longest to replace. Using this method an individual can donate plasma or platelets
much more frequently than they can safely donate whole blood.[51]
These can be combined, with a donor giving both plasma and platelets in the
same donation.
Platelets can also be separated from whole blood,
but they must be pooled from multiple donations. From three to ten units of
whole blood are required for a therapeutic dose.[52]
Plateletpheresis provides at least one full dose from each donation.
Plasmapheresis is frequently used to collect source plasma
that is used for manufacturing into medications much like the plasma from whole
blood. Plasma collected at the same time as plateletpheresis is sometimes
called concurrent plasma.
Apheresis is also used to collect
more red blood cells than usual in a single donation (commonly known as "double reds") and to collect white blood cells
for transfusion.[53][54]
Recovery
and time between donations
Donors are usually kept at the
donation site for 10–15 minutes after donating since most adverse reactions
take place during or immediately after the donation.[55]
Blood centers typically provide light refreshments or a lunch allowance to help
the donor recover.[56]
The needle site is covered with a bandage and the
donor is directed to keep the bandage on for several hours.[39]
In hot climates, donors are advised to avoid dehydration (strenuous games,
alcohol) until a few hours after donation.
Donated plasma is replaced after 2–3
days.[57]
Red blood cells are replaced by bone marrow into the circulatory system at a
slower rate, on average 36 days in healthy adult males. In one study, the range
was 20 to 59 days for recovery.[58]
These replacement rates are the basis of how frequently a donor can donate
blood.
Plasmapheresis and plateletpheresis
donors can donate much more frequently because they do not lose significant
amounts of red cells. The exact rate of how often a donor can donate differs
from country to country. For example, plasmapheresis donors in the United
States are allowed to donate large volumes twice a week and could nominally
give 83 liters (about 22 gallons) in a year, whereas the same donor in Japan
may only donate every other week and could only donate about 16 liters (about 4
gallons) in a year.[59]
Red blood cells are the limiting step for whole blood donations, and the
frequency of donation varies widely depending on the type of donor and local
policies. For example, adult men in Hong Kong can donate once every three
months, women every four months, and youth aged sixteen or seventeen only every
six months.[60]
In Canada and the United States it is 56 days for any type of donor.[61][62]
Complications
Donors are screened for health
problems that would put them at risk for serious complications from donating.
First-time donors, teenagers, and women are at a higher risk of a reaction.[63][64]
One study showed that 2% of donors had an adverse reaction to donation.[65]
Most of these reactions are minor. A study of 194,000 donations found only one
donor with long-term complications.[66]
In the United States, a blood bank is required to report any death that might
possibly be linked to a blood donation. An analysis of all reports from October
2008 to September 2009 evaluated six events and found that five of the deaths
were clearly unrelated to donation, and in the remaining case they found no
evidence that the donation was the cause of death.[67]
Hypovolemic reactions can occur because of a rapid change in blood pressure.
Fainting is
generally the worst problem encountered.[68]
The process has similar risks to
other forms of phlebotomy. Bruising of the arm from the needle insertion is the most common
concern. One study found that less than 1% of donors had this problem.[69]
A number of less common complications of blood donation are known to occur. These
include arterial puncture, delayed bleeding, nerve irritation, nerve injury,
tendon injury, thrombophlebitis, and allergic reactions.[70]
Donors sometimes have adverse
reactions to the sodium citrate used in apheresis
collection procedures to keep the blood from clotting. Since the anticoagulant
is returned to the donor along with blood components that are not being
collected, it can bind the calcium in the donor's blood and cause hypocalcemia.[71]
These reactions tend to cause tingling in the lips, but may cause convulsions,
seizure, hypertension, or more serious problems.[72]
Donors are sometimes given calcium supplements during the donation to prevent
these side effects.[73]
In apheresis
procedures, the red blood cells are returned. If this is done manually and the donor
receives the blood from a different donor, a transfusion reaction can take place. Manual apheresis is extremely rare in the
developed world because of this risk and automated procedures are as safe as
whole blood donations.[74]
The final risk to blood donors is
from equipment that has not been properly sterilized. In most cases, the equipment that comes in direct contact
with blood is discarded after use.[75]
Re-used equipment was a significant problem in China in the 1990s, and up to 250,000 blood plasma donors may
have been exposed to HIV from shared equipment.[76][77]
Storage,
supply and demand
Storage
and blood shelf life
The collected blood is usually
stored in a blood bank as separate components, and some of these have short shelf
lives. There are no storage solutions to keep platelets for extended
periods of time, though some are being studied as of 2008.[78]
The longest shelf life used for platelets is seven days.[79]
Red blood cells (RBC), the most
frequently used component, have a shelf life of 35–42 days at refrigerated
temperatures.[80][81]
For (relatively rare) long-term storage applications, this can be extended by
freezing the blood with a mixture of glycerol, but this
process is expensive and requires an extremely cold freezer for storage.[37]
Plasma can be stored frozen for an
extended period of time and is typically given an expiration date of one year
and maintaining a supply is less of a problem.[82]
Demand
for blood
The limited storage time means that
it is difficult to have a stockpile of blood to prepare for a disaster. The
subject was discussed at length after the September 11 attacks in the United States, and the consensus was that collecting
during a disaster was impractical and that efforts should be focused on
maintaining an adequate supply at all times.[83]
Blood centers in the U.S. often have difficulty maintaining even a three day
supply for routine transfusion demands.[84]
Donation
levels
The World
Health Organization recognizes World Blood Donor Day on
14 June each year to promote blood donation. This is the birthday of Karl Landsteiner,
the scientist who discovered the ABO blood group system.[85]
The theme of the 2012 World Blood Donor Day campaign, "Every blood donor
is a hero" focuses on the idea that everyone can become a hero by giving
blood. As of 2008, the WHO estimated that more than 81 million units of blood
were being collected annually.[86]
In the United States it is estimated
that only 111 million citizens are eligible blood donors,[87]
or 37% of the population.[88]
However less than 10% donate annually.[88]
In the UK the NHS reports blood donation levels at "only 4%".[89]
Donor
health benefits
In patients prone to iron overload,
blood donation prevents the accumulation of toxic quantities.[90]
Donating blood may reduce the risk of heart disease for men, but the link has
not been firmly established and may be from selection bias
because donors are screened for health problems.[91][92]
Research published in 2012
demonstrated that repeated blood donation is effective in reducing blood pressure,
blood glucose,
HbA1c, low-density lipoprotein/high-density lipoprotein ratio,
and heart rate.[93]
Donor
compensation
The World Health Organization set a
goal in 1997 for all blood donations to come from unpaid volunteer donors, but
as of 2006, only 49 of 124 countries surveyed had established this as a
standard.[12]
Some countries, such as Tanzania, have made great strides in moving towards this standard,
with 20 percent of donors in 2005 being unpaid volunteers and 80 percent in
2007, but 68 of 124 countries surveyed by WHO had made little or no progress.[5]
Many plasmapheresis donors in the United States
are still paid for donations.[94]
A few countries rely on paid donors to maintain an adequate supply.[95]
In some countries, for example Brazil and Australia, it is illegal to receive any compensation, monetary or
otherwise, for the donation of blood or other human tissues.[96][97]
Regular donors are often given some
sort of non-monetary recognition. Time off from work is a common benefit.[98]
For example, in Italy, blood donors receive the donation day as a paid holiday
from work.[99]
Blood centers will also sometimes add incentives such as assurances that donors
would have priority during shortages, free T-shirts, first aid kits, windshield
scrapers, pens, and similar trinkets. There are also incentives for the people
who recruit potential donors, such as prize drawings for donors and rewards for
organizers of successful drives.[100]
Recognition of dedicated donors is common. For example, the Singapore
Red Cross Society presents awards for voluntary donors who have made a certain
number of donations under the Blood Donor Recruitment Programe starting with a
"bronze award" for 25 donations.[101]
The government of Malaysia also offers free outpatient and hospitalization benefits
for blood donors, for example, 3 months of free outpatient treatment for every
donation.[102]
In Poland, after donating specific amount of blood (18 liters for men and 15
for women) a person is gifted with title of "Distinguished Honorary Blood
Donor" as well as a medal.
Most allogeneic blood donors donate
as an act of charity and do not expect to receive any direct benefit from the
donation.[103]
The sociologist Richard Titmuss, in his 1970 book The Gift Relationship: From Human
Blood to Social Policy, compared the merits of the commercial and
non-commercial blood donation systems of the USA and the UK. The book became a
bestseller in the USA, resulting in legislation to regulate the private market
in blood.[104]
The book is still referenced in modern debates about turning blood into a
commodity.[105]
The book was republished in 1997 and the same ideas and principles are applied
to analogous donation programs, such as organ donation
and sperm.
The entire wiki link can be found at:
http://en.wikipedia.org/wiki/Blood_donation
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