What are transfusions?

Despite all our medical advances, there is still no good man-made substitute for human blood, which is why blood donations are so important. People donate blood for different reasons -- some do it for friends, family members, or even themselves. Others volunteer so that they can help people they don't even know.

Blood is usually donated at special collection centers. Some centers use vans (often called bloodmobiles) that travel to different areas to collect blood donations. Some larger hospitals have their own centers to collect and process donated blood. After blood is tested for safety and processed into components, it is sent to blood banks, where it is stored until needed.

Keeping the blood supply safe

In the United States, all blood centers follow careful procedures to keep the blood supply safe. Everyone who comes in to donate is asked many questions and has a chance to say whether their blood may be unsafe for any reason. Also, previous donation records and lists of ineligible donors are checked. Lab tests are done to look for blood that might transmit diseases (described in "Possible risks of blood product transfusions"). People are not allowed to donate blood if their lab tests or questionnaires show that they may be at high risk for certain diseases.

In response to learning that TRALI is linked to certain donor antibodies, blood banks are now screening donors to avoid transfusing plasma from people who are likely to have these antibodies. Other parts of the blood are used as usual, but the donors' plasma is not given to patients -- it may be used to make medicines.

The US Food and Drug Administration (FDA) considers blood a "biologic" (much like a drug) and closely regulates it to ensure the safety of the blood supply. The American Association of Blood Banks also publishes guidelines for safe transfusions, which its members must follow.

Donating blood is safe

Rules on who can donate help protect the donor as well as the recipient.

Aside from protecting those who receive donated blood, rules are also in place to protect people who want to donate. Although guidelines can vary slightly by state and facility, for the most part donors must:

• Be healthy
• Be at least 17 years old
• Weigh at least 110 pounds
• Not have donated blood within the past 8 weeks (this can be shorter for most apheresis donations)
• Not be taking antibiotics

People who are taking "blood thinners" or certain drugs that are used to treat acne, baldness, or an enlarged prostate may not be able to donate unless they've stopped the drug for a few days or weeks. People who have taken certain drugs for psoriasis or taken products made from human plasma or tissues may be kept from donating blood even longer. There are other health and travel questions that are reviewed with each donor in detail. (See "The donation process" below.)

Other safety details

Only sterile equipment is used to collect blood. The needle used to draw blood from your vein has never been used before, and it is thrown away right after it is used. Donors cannot get hepatitis, HIV, or other infections or diseases from giving blood. Reactions from donating are rare and are almost always minor when they do happen. If you are healthy, you can donate a unit (about a pint) of blood without harm because one unit is a small part of your total blood volume. Your body will replace the lost fluid within a day, and your bone marrow will replace all of the blood cells, usually within a couple of weeks.

If you are interested in donating blood, contact the American Association of Blood Banks (AABB) for a list of member institutions, or visit their online blood bank locator. Or you can contact America's Blood Centers or the American Red Cross for donation centers near you. (See the "Additional resources" section for contact info.)

The donation process

Before giving blood, get a good night's sleep, eat a well-balanced meal, and drink extra fluids that are caffeine-free. Some donor centers ask that you bring in a list of all the medicines you are taking.

FDA guidelines require that before giving blood, you must register, have your vital signs checked, answer health questions, and get a blood test (usually by sticking the finger for a few drops of blood). The center will have you fill out a questionnaire, asking about certain behaviors or travel that might put you at increased risk for certain diseases. You must also be informed about donation before you decide to donate and actually give the blood.

You will be asked to sit in a reclining chair or lie on a table. An area on your arm will be cleaned, and a sterile needle put into a vein (usually where your elbow bends). Removing a unit of whole blood usually takes only about 10 to 15 minutes. Apheresis donation (described below in the section, "Types of donation") may take 2 hours or longer.

Once your blood is taken, you will be asked to stay for a short time to make sure you are feeling well. During this time you are encouraged to drink fluids (such as fruit juice) and eat a light snack before leaving. The whole process, from registration to snack, takes about an hour. Although you can take part in normal activities soon after giving blood, some centers recommend that you have someone else drive home after you donate. You may feel tired, but this will usually only last a few hours.

Types of donations

There are several types of blood product donations.

Volunteer whole blood donation: Most blood donations come as units of whole blood from volunteers who have no connection to the person who will receive it. Once donated, the units are usually separated into component parts.

Apheresis donation: Apheresis allows volunteers to donate just one blood component. Blood is drawn out through a vein in the arm, and a machine separates out the needed component (usually platelets, although red blood cells, white blood cells, and plasma can also be collected this way). The rest of the blood is then returned to the donor, usually through a vein in the other arm. This procedure usually takes 2 or more hours.

The advantage of this type of donation is that, since most of the blood is returned, a large amount of a needed component can be collected. Patients who need many platelet transfusions, such as some cancer patients, are exposed to fewer donors in this way than they would be from pooled platelets coming from many donors. This cuts down on the risk of both transfusion reactions and infections.

As with whole blood donation, apheresis donors should:

• Get a good night's sleep.
• Eat a well-balanced meal.
• Drink extra caffeine-free fluids before donating.

Since aspirin makes platelets less useful to a transfusion recipient, donors are usually asked not take aspirin within 36 hours before donation. The same FDA guidelines as those for whole blood donation must be followed. Unlike whole blood donors, those who give platelets or plasma via apheresis usually can give again in a couple of weeks. Different blood centers may have different rules about this.

During the apheresis procedure, donors may feel cold, or they may feel a slight tingling sensation around the lips and nose, but this goes away once the procedure is completed. (It is caused by the drug that is used to keep the blood from clotting in the machine.) Other side effects, such as feeling tired, are much like those from whole blood donation.

Autologous blood donation: Donating your own blood for later use is called autologous (meaning "from the self") donation. Autologous donation is most often done in the weeks before you have a scheduled surgery that will likely require blood transfusion. The blood can then be used during or after the operation to replace any blood you may have lost. This is generally thought to be the safest form of blood transfusion because you're getting your own blood back. But it is not totally without risk. There is always the very small chance that bacterial contamination or clerical errors can happen. People who aren't able to donate blood for others may still be able to donate blood for themselves.

There is a processing fee for collecting, testing, storing, and delivering each unit of autologous blood. Be aware that your health insurance may not fully reimburse you for this cost. There is also a need to plan ahead so that you have enough time before surgery to have your blood cell counts go back to normal levels after blood has been collected.

Directed donation: Donating blood for a family member, friend, or other specified patient is called directed donation. This can be done at any blood donation center. The donor must meet the same requirements as for regular blood donation, and the donor's blood must be compatible with (match the blood type of) the recipient.

Blood from directed donors is not usually any safer than blood from other volunteer donors and in some cases may actually be more likely to cause problems. (See "Graft-versus-host disease" under "Transfusion reactions" in the section "Possible risks of blood product transfusions.") The same types of testing are still done on blood from directed donors. As with autologous donation, there is a processing fee for collecting, testing, and delivering each unit of directed donor blood. This fee may not be fully reimbursed by health insurance.

Paid donation: Blood from paid donors cannot be used in the United States for transfusion purposes. Plasma is the only component for which donors are sometimes paid, and it is taken by the apheresis method. Plasma can be treated for safety in ways that blood cells cannot. Plasma taken from paid donors is generally treated and processed by pharmaceutical companies into drugs. It cannot be transfused in the form of cryoprecipitate or fresh frozen plasma.