Blood donation

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

Process

The process of giving blood involves screening the donor, the actual donation, and a brief recovery period.

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This applies to both whole blood donations and plasmapheresis (giving of plasma only) - see Donation below.

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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 US, these practices have been eliminated, and donor attributes are considered only in terms of their likelihood to affect the probablity of transmission of disease. All blood products in the U.S. are labelled as coming from either a "volunteer donor" or a "paid donor", with the latter being more likley to transmit infection. Other donor characteristics are also taken into account: the American Red Cross and Food & Drug Administration policies prohibit accepting blood donations from gay men, specifically from any "male who has had sex with another male since 1977, even once," http://www.harbus.org/main.cfm?include=detail&storyid=171199&page=2 or from IV drug users or recent immigrants from certain nations with high rates of HIV infection. While the inclusion of gay 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.

Related Topics:
American Red Cross - Food & Drug Administration

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When a donor arrives at a donation site, the donor typically fills out a consent form as well as answering a brief survey 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), recent international travel, and sexual history. Answers are associated with your blood, but not your name to provide anonymity.

Related Topics:
Consent - Survey - Age - Weight - Health - Tattoo - Drug - Recreational - Travel - Sexual

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

Related Topics:
Hemoglobin - Phlebotomist

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• hematocrit: done in some places. requires a centrifuge. A measurement of >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.

Additionally, the donor may indicate to not use their blood but still go through the blood drawing process, again to protect the individual's medical privacy. All blood is later tested for diseases including STDs. If a disease is found, the donor will be notified and their blood discarded. It is discouraged for individuals to use blood donation as anonymous STD screening.

Related Topics:
Medical privacy - STD

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Donation

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. Typically, around 500 millilitres, about a pint, is drawn during the blood donation process.

Related Topics:
Elbow - Cannula - Vein - Tourniquet - Scale - Millilitre - Pint

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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.

Related Topics:
Apheresis - Blood type

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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.

Related Topics:
Centrifuge - Apheresis - Platelets - Plasma

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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. In some countries, stickers are worn by donors to show the donor's pride and 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. 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.

Related Topics:
Bandage - Gauze - Blood sugar

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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.

Related Topics:
Cryopreservation - Cell - Glycerol - Cryoprotectant

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