Blood donation

"Give blood" redirects here. For other uses, see Give blood (disambiguation).

Blood donation is a process by which a blood donor voluntarily has blood drawn for storage in a blood bank or for subsequent use in a blood transfusion.

Blood donation

Blood donations may be scheduled at local centres, or at times a "blood drive" will occur. These are events where a blood bank or other blood collecting organization will set up in a convenient location—such as a shopping centre, large employer, university, or a local church—for people to stop in without appointment during their daily routine to donate blood. Sometimes a bloodmobile is used to run a blood drive. Usually a modified recreational vehicle, it is an easy place to run a blood drive because it is already set up for the process of blood donation. Many blood banks have several bloodmobiles so they can serve many people at once.

Process

The process of giving blood involves screening the donor, the actual donation, and a brief recovery period. This applies to both whole blood donations and plasmapheresis (donating only one's plasma) - see Donation below.

Before arriving at the donation site

In the days prior to donating blood, it is important that donors prepare themselves for a process that can temporarily weaken the body. Donors should check their local blood bank's guidelines, as requirements and recommendations vary. Many blood banks recommend that potential donors drink extra water and fluids before donating. It may be advisable to avoid caffeinated beverages before donation. Eating well is also important, and can reduce the risk of reactions to donation. Eating foods high in iron (which has many dietary sources) is also a good idea; low hemoglobin levels may make a donor temporarily ineligible. This is especially true for women who have menstruated recently, because of iron loss in the menses. Some countries require donors to observe a limited or full fast before donation because of specific screening methods; in particular, some countries will discard blood taken too soon after a fatty meal.

Screening

Western countries typically impose screening for blood donor candidates. In the past, it was the practice in America and other countries to separate blood donations on the basis of race, ethnicity, or religion, or to exclude certain groups from the donor pool on those bases. Currently, in the United States, these practices have been eliminated, and donor attributes are considered only in terms of their likelihood to affect the probability of transmission of disease. All blood products in the U.S. are labeled as coming from either "paid" or "volunteer" donors, with paid units being more likely to transmit infection. (Several other countries avoid paid donations altogether for this reason.)

Blood donation at the Royal Melbourne Hospital during the 1940s.

Other donor characteristics are also taken into account: starting in 1985, the American Red Cross and Food and Drug Administration policies prohibit accepting blood donations from gay/bisexual men, specifically from any "male who has had sex with another male since 1977, even once," or from IV drug users or recent immigrants from certain nations with high rates of HIV infection. The inclusion of men who have sex with men on the prohibited list has created some controversy; the FDA & Red Cross cite the public policy need to protect the blood supply from HIV & similar diseases as justification for the ban, while others believe the ban to be discriminatory, since sexually active heterosexuals are not categorically banned and all donated blood is screened. Policies vary in other countries; for instance, Australia formerly had a similar ban, but now only prohibits donating blood within one year after male-male sex (longer than the typical window period for HIV blood screening tests performed on donated blood).

Similarly important donor eligibility requirement in the US is related to concerns about variant Creutzfeldt-Jakob Disease (vCJD): persons who have spent long periods of time in countries where "mad cow disease" is found are not eligible to donate. As part of the screening interview, blood donors are questioned about past residency in countries on the exclusion list, tracing back as far as 1980. The list of countries of residence that may disqualify a potential donor includes most of Western Europe (with stronger restrictions on those with past residence in the United Kingdom), Turkey, and all of Eastern Europe except Russia, Ukraine, Belarus, and the Baltic countries (those formerly part of the Soviet Union). From 1980 through 1996, if a person visited or resided in country on the exclusion list for a time that adds up to five years or more, the person is not eligible to donate; if a person spent time that adds up to three months or more in the United Kingdom, they are indefinitely deferred. This set of rules affects members of the US Armed Forces and others, who lived at least six months in certain European countries or 3 months in the United Kingdom from 1980 to 1996, who are therefore prohibited from donating blood. A similar policy with regard to vCJD applies in Quebec and in the rest of Canada.

When a donor arrives at a donation site, they typically fill out a consent form as well as answer an extensive questionnaire to help determine their eligibility. Questions include the donors' age, weight, most recent donation, current health, and various risk factors such as tattooing, drug use (recreational or performance enhancing), residency abroad, recent international travel, and sexual history. Answers are associated with the donor's blood, but not name, to provide anonymity.

Often the blood hemoglobin concentration will be checked next, typically performed by a phlebotomist. While various tests exist, the most common ones are:

• hematocrit: done in some places. requires a centrifuge. A measurement of no less than 38% allows donation to continue.
• colorimetric hemoglobin test using a hemoglobin photometer: a machine-read result from a chemical reaction on a testing strip.
• copper sulfate screening test (aka "float test"): measures the specific gravity of the donor's blood by placing a drop into a copper sulfate solution. The solution is calibrated so that a hemoglobin concentration of in >12.5 g/dl (the cut-off in the U.S. for donation) sinks.

All blood is later tested for diseases, including STDs. If a disease is found, the donor will be notified and their blood discarded. Individuals are discouraged from using blood donation for the purpose of anonymous STD screening. Blood may also be tested for additional infectious diseases such as West Nile Virus, when and where these diseases are prevalent.

Donation

Disinfect, insert the cannula, pull out the cannula, dress the wound.

The blood donation itself happens next. The donor lies supine on a cushioned bench and extends an arm. The inner elbow is disinfected, and a cannula is inserted into a vein. The donor often has a tourniquet wrapped around his or her arm, or may be prompted to squeeze a ball repeatedly, to help speed the process. Blood flows from the vein, through the needle and a tube, and into a special collection bag which is placed on a small scale to measure the amount of blood withdrawn. After the bag is sufficiently filled, several test tubes are drawn from the same needle to be used for disease detection. Typically, around 450 millilitres, about a pint, is drawn during the blood donation process.

A relatively large-bore needle is used for whole blood donations.

A mechanical tray tilts the bag to prevent congealing, and displays current volume and flow per minute.

Apheresis

Rather than donating whole blood, a donor sometimes has the option to donate only some blood components while retaining others. This process is known as apheresis, and is more involved, time consuming, and requires more specialized equipment. The benefit is that more of the desired components can be concentrated and removed, and the donor is usually able to donate significantly more frequently than if whole blood had been removed. In some cases, the usefulness of the removed components is not as sensitive to blood type considerations.

The typical method of apheresis is to draw whole blood from the donor, then centrifuge the blood to separate its components (see apheresis for more information). The desired components (e.g. platelets, plasma) are removed and then the remaining components are returned to the donor.

Recovery

Once the donation is complete, the donor is given a bandage or gauze to stop further blood flow and is normally allowed to leave. Beverages and snacks may be provided to restore blood volume and blood sugar, and to settle the stomach. Often donors are encouraged to sit down for a few minutes to return to normality, as lightheadedness and faintness may occur. In some countries, stickers are worn by donors to show the donor's pride and to encourage others to give. The entire process, from screening through recovery, takes about one hour. The actual blood donation takes between four and fifteen minutes for whole blood donation. Donors are discouraged from heavy exercise or lifting until the next day. Plasma volumes will return to normal in around 24 hours, while red blood cells are replaced by bone marrow into the circulatory system within about 3-5 weeks, and lost iron replaced over 6-8 weeks. This recovery process can be speeded by eating foods high in complex carbohydrates, iron, and other trace minerals. Due to the time frame required for iron replacement, donors are eligible to donate whole blood approximately eight to twelve weeks after the previous donation (the exact period varying by country); in the USA, the waiting period for the two red cell units apheresis donors is 112 days.

Storage

Cryopreservation of red blood cells is done to store special, rare red blood cells for up to 10 years. The cells are first incubated in a 40% glycerol solution which acts as a cryoprotectant ("antifreeze") within the cells. The units are then placed in special sterile containers in a deep freezer at less than -60°C.

Donors for babies

A tiny percentage of adults may donate blood to small children in emergency rooms, newborn babies, and fetuses. To ensure the safety of blood transfusion to pediatric patients, including those in whom the immune systems are not fully developed, hospitals are taking every precaution to avoid infection and prefer to use specially tested pediatric blood units that are guaranteed negative for Cytomegalovirus, because the consequences of CMV infection for newborns or low weight infants may be severe or even fatal. Additionally, for pediatric patients with certain disorders or in emergency, when there is no time to perform crossmatching, only O/Rh negative blood can be used for neonatal transfusion. Due to these specific restrictions, to be recognized as a baby donor an adult must test negative for Cytomegalovirus, and some blood collection agencies such as Red Cross also require baby donors that they be blood type O-negative. Since only 7% of US adults are O-negative and as few as 15% of adults do not carry Cytomegalovirus, only 1% of adults may qualify as baby donors. Other restrictions (body weight, HIV status, vCJD, etc. ) reduce the fraction of potential baby donors to less than 1 in 200. If an adult was not exposed to Measles, Mumps, Rubella, or chicken pox, that amplifies the person's status as a baby donor.

Newborn babies that require multiple surgeries often need up to 20 units of blood in their first few weeks.

Complications

The finger prick and needle insertion typically cause only minor discomfort. Phlebotomists may, however, experience difficulties in obtaining enough blood from some donors.

During or shortly after the donation, hypovolemia may occasionally lead to a drop in blood pressure, with some donors experiencing light-headedness or fainting. In some cases this may necessitate cancelling the donation, restoring blood volume with an intravenous infusion, or placing the donor in a Trendelenburg position (on a stretcher tilted "legs up"). Beverages may be given to replenish blood volume further, and the donor may have to remain in a horizontal position for a while under monitoring. Most blood banks encourage donors to rest for several minutes after donation (often while eating and drinking) to let them adjust to the loss of blood and reduce the risk of these problems.

In less than 1% of cases, improperly inserting the needle is followed by bruising of the arm in the weeks afterwards.

Negative medical reactions to blood donation are rare, and blood bank staff are trained to handle them.

Benefits

Donating blood may reduce the risk of heart disease for men and stimulate the generation of red blood cells. In patients prone to iron overload (e.g. due to hemochromatosis), blood donation prevents the accumulation of iron. (Note: At this time the American Red Cross does not accept people with hemochromatosis to donate blood for other people.)

The amount of toxic chemicals (e.g. mercury, pesticides, fire retardants) circulating in the blood stream is reduced by the amount contained in given blood.

Anecdotally, elderly people in good health have reported feeling invigorated by giving blood on a regular basis.

Autologous donation

A person who anticipates the need for a blood transfusion at a later date (usually because of scheduled surgery) may make an autologous donation, in which their blood is stored and later transfused back into its original donor. Besides ensuring the availability of compatible blood (especially important for patients with rare blood types), this procedure also eliminates the risk of disease transmission from infected donors.

See also

• List of blood donation agencies
• Blood transfusion
• Plateletpheresis

External links

• Blood Donation and Processing
• FAQs and donor information from the American Red Cross
• USA Directory of Blood Donation Centers
• UK National Blood Service