Blood donation
From Free net encyclopedia
Template:Redirect 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.
Image:Blood donation at Fleet Week USA.jpg
To understand the importance of the availability of a sustainable donated blood supply, the catch-cry of the Australian Red Cross Blood Service is, "80% of Australians will need blood in their lifetime, but less than 3% of Australians give blood each year." In the United States, the odds of knowing someone who will need blood are "97%", according to that branch of the Red Cross.
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.
Contents |
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. Perhaps the most important thing is to eat and drink well. By drinking plenty of fluids the day before and of the donation, the donor can help prevent hypovolemia. Eating well is also important, partly because it can also help with hydration, but mostly because high nutrient levels give the body the raw materials it needs to respond quickly to the loss of blood. Eating regular, well-balanced meals in the days before the donation is important, but it is especially critical to have a good, low-fat meal before the donation. Eating foods high in iron (which has many dietary sources) is also a good idea for those giving whole blood or red blood cells. Finally, activities that promote general physical fitness (such as exercise, sex, and sleep) are all especially wise in the several days before a donation. However, donors should check their local blood bank's guidelines; some countries require donors to fast before donation to avoid interfering with screening.
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 labelled 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.)
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," Template:Ref or from IV drug users or recent immigrants from certain nations with high rates of HIV infection. While the inclusion of homosexual/bisexual 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. 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 tests performed on donated blood).
Similarly important donor eligibility requirement in the US is related to concerns about variant Creutzfeld-Jacob Disease (vCJD): persons who have spent long periods of time in countries where "mad cow disease" is found Template:Ref, 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 disqualify a potential donor if a person had resided in a country for six or more months between 1980 and 1996, 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).
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 >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 for the purpose of anonymous STD screening.
Donation
Image:Blood donation needle.jpg
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.
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. 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. 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 process can be speeded by eating foods high in complex carbohydrates, iron, and other trace minerals.
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.
Complications
Finger prick and needle insertion typically cause only minor discomfort. Phlebotomists may however experience difficulties in obtaining enough blood from some donors.
During the donation, hypovolemia may occasionally lead to a drop in blood pressure with some donors experiencing light-headedness. 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 further replenish blood volume, and the donor may have to remain in a horizontal position for a while under monitoring.
In less than 1% of cases, improperly inserting the needle is followed by bruising of the arm in the weeks afterwards [1].
Negative medical reactions to blood donation are rare and blood bank staff are trained to handle them.
Benefits
Donating blood may reduce risk for heart disease, and stimulates the generation of red blood cells. In patients prone to iron overload (e.g. due to hemochromatosis), blood donation prevents the accumulation of iron.
Anecdotally, elderly people in good health have reported feeling invigorated by giving blood on a regular basis.
The psychological benifits of donating blood is the sense the donor has that he/she has made a contribution and help save a person's life.
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
Footnotes
External links
- Blood Donation and Processing
- FAQs and donor information from the American Red Crosscs:Darování krve
da:Bloddonor de:Blutspende es:Donación de sangre fr:Don de sang it:Donazione del sangue ja:献血 no:Blodgivning fi:Verenluovutus sv:Blodgivning zh:无偿献血