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Encyclopedia > Plateletpheresis

Plateletpheresis (also called thrombapheresis or thrombocytapheresis) is a special type of blood donation that only extracts platelets, the cells that cause blood clotting, from the blood. It helps to reduce undesirable transfusion side effects caused by co-existing blood components. 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. ... A 250 ml bag of newly collected platelets. ... Coagulation is the thickening or congealing of any liquid into solid clots. ...

The separation of individual blood components is done with a specialized centrifuge (see apheresis). The earliest manual forms of plateletpheresis are done by the separation of platelets from multiple bags of whole blood collected from donors or blood sellers. Since each blood bag (usually 250 ml or 500 ml) contains a relatively small number of platelets, it can take as many as a dozen blood bags (usually from 5 to 10 bags, depending on the size of the blood bags and each donor's platelet count) to accumulate a single unit of platelets (enough for one patient). This greatly increases the risks of the transfusion. Each unit of platelets separated from donated whole blood is called a "platelet concentrate". A laboratory centrifuge tabletop centrifuge A centrifuge is a piece of equipment that puts a substance in rotation around a fixed axis in order for the centrifugal force to separate a fluid from a fluid or from a solid substance. ... Whole blood enters the centrifuge on the left and separates into layers so that selected components can be drawn off on the right. ... Red blood cells (erythrocytes) are present in the blood and help carry oxygen to the rest of the cells in the body Blood is a circulating tissue composed of fluid plasma and cells (red blood cells, white blood cells, platelets). ...

Modern automatic plateletpheresis allows the blood donor to give a portion of his platelets, while keeping his red blood cell and at least a portion of blood plasma. Therefore, no more than three units of platelets are generally harvested in any one sitting from a donor. Human red blood cells Red blood cells are the most common type of blood cell and are the vertebrate bodys principal means of delivering oxygen to body tissues via the blood. ... Blood plasma is the liquid component of blood, in which the blood cells are suspended. ...

Because platelets have a life-span of just 5 days, more platelet donors are always needed.



As with all forms of blood donation, the donor must meet certain health requirements, as well as having an acceptable blood chemistry and a certain amount of time between donations.

Other collected components

Even though red blood cells can also be collected in the process, most blood donation organizations do not do so because it takes much longer for the human body to replenish their loss. If the donor donates both red blood cells and platelets, it takes months, rather than days or weeks, before they are allowed to donate again (the guidelines regarding blood donation intervals are country-specific).

In most cases, blood plasma is returned to the donor as well. However, in locations that have plasma processing facilities, a part of the donor's plasma can also be collected in a separate blood bag (see plasmapheresis). Plasmapheresis is the removal of (components of) blood plasma from the circulation. ...


Due to their higher relative density, white blood cells are collected as an unwanted component with the platelets. Since it takes up to 3 liters of whole blood (the amount of a dozen of blood bags) to generate a dose of platelets, white blood cells from one or several donors will also be collected along with the platelets. A 70 kg (154 lb) man has only about 6 liters of blood. If all of the incidentally collected white blood cells are transfused with the platelets, substantial rejection problems can occur. Therefore, it is standard practice to filter out white blood cells before transfusion by the process of leukoreduction. Relative density (also known as specific gravity) is a measure of the density of a material. ... Leukoreduction is the reduction of white blood cells or leukocytes from the blood or blood components being transfused to the recipient. ...

Early platelet transfusions used a filter to remove white blood cells at the time of transfusion. It takes a trained person about 10 minutes to assemble the equipment, and this is not the safest or most efficient means of filtration because living white blood cells can release cytokines during storage and dead white blood cells can break up into smaller fragments that can still stimulate a dangerous response from the immune system. In addition, simple filtration can lead to increased risks of infection and loss of valuable platelets. Newer, more advanced plateletpheresis machines can filter white blood cells during separation. Cytokines are small protein molecules that regulate communication among immune system cells and between immune cells and those of other tissue types. ...

For example, with marginally acceptable whole blood (white blood cells: < 10,000/mm3; platelets: > 150,000/mm3), a dose (3×1011) of platelets comes with about 2×1010 white blood cells. This can seriously damage the patient's health. A dose of single-donor platelets prepared using latest filters can contain as little as 5×104 white blood cells.

Manual platelet apheresis

There are two types of manual platelet apheresis. Platelet-rich plasma (PRP) is widely used in North America and Buffy coat (BC) is more widely used in Europe. Buffy coat is the fraction of a centrifugated blood sample that contains most of the white blood cells. ...

Automatic platelet apheresis

Platelets are the clotting factor of your blood (i.e. what helps a cut scab over so you don't bleed to death), and when donated, frequently go to cancer patients, because due to chemotherapy mnay cancer patients are unable to generate enough platelets of their own. A 250 ml bag of newly collected platelets. ... Chemotherapy is the use of chemical substances to treat disease. ...

The basic principles of automatic platelet apheresis are the same as in the manual procedure, but the whole procedure is performed by a computer-controlled machine. Since the donor's blood is processed in a sterile single-use centrifuge, the unwanted components can be returned to the donor safely. This allows the apheresis machine to repeat the draw-centrifuge-return cycle to obtain more platelets. The bulk of the machine, and the length of the donation process means most platelet donations are done in blood centers instead of moblie blood drives. Whole blood enters the centrifuge on the left and separates into layers so that selected components can be drawn off on the right. ...

A platelet donor must usually weigh at least 50 kg (110 lb) and have a platelet count of at least 150×105/mm3. Each country has its own rules to protect the safety of both donor and recipient. One unit has about 3×1011 platelets. Therefore, it takes 2 liters of blood having a platelet count of 150×105/mm3 to produce one unit of platelets. Some regular donors have higher platelet counts (over 300×105/mm3); for those donors, it only takes about one liter of their blood to produce a unit. Since the machine used to perform the procedure uses suction to pull blood out of your body, some people that can give whole blood may have veins too small to use for platelet donation. Your blood center can evaluate you prior to donation.

Blood accounts for about 8% of body weight, giving a 50 kg donor about four liters of blood. No more than 50% of platelets are ever extracted in one sitting, and they can be replenished by the body in about three days.

Most newer apheresis machines can separate a dose of platelets in about 60 to 120 minutes depending on the donor's health condition.

Donation process

After a mini-physical, you are taken into the donation room and sit in a chair next to the machine. The tech cleans one arm with iodine and inserts the needle. The process takes about one to two hours while blood is pulled into the machine, spun around, and replaced along with an anticoagulant, usually Sodium Citrate. You may have the option of donating a unit of plasma with the platelets, if you choose. Your blood is pulled into the machine and returned to you usually about 6-8 times, accounting for the length of the donation. An anticoagulant is a substance that prevents coagulation; that is, it stops blood from clotting. ...

Occasional side effects of the donation of platelets include tingling, slight nausea, bruising, fatigue, and dizziness. Frequently while donating your lips may begin to tingle; the techs usually keep a supply of Tums close by because the anticoagulant works by binding to the calcium in your blood. Since Calcium is used in the operation of the nervous system, nerve-ending-dense areas (like your lips) are suscepible to the tingling. Usually chewing a handful of tums will raise calcium levels and relieve the tingling. Bruising may also occur. Fatigue and dizziness is generally not as common after donating platelets as it is after donating blood because you get your red blood cells back. An antacid is any substance that counteracts stomach acidity. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ...

Aside from the procedure, donating platelets is different from donating blood in a few ways.

First, you cannot take aspirin for anywhere from 36 to 72 hours prior to your donation. (Guidelines vary by blood center.) The reason for this is that aspirin is a potent drug that prevents platelets from working. Some blood centers also prohibit the taking of ANY NSAID (non-steroidal-anti-inflammatory-drug) for 36-hours prior. Different centers have different policies, so contact the center before donating. Aspirin or acetylsalicylic acid is a drug in the family of salicylates, often used as an analgesic (against minor pains and aches), antipyretic (against fever), and anti-inflammatory. ... Non-steroidal anti-inflammatory drugs, usually abbreviated to NSAIDs, are drugs with analgesic, antipyretic and anti-inflammatory effects - they reduce pain, fever and inflammation. ...

Second, you may be able to dontate platelets every three days, up to 26 times a year. This is a stark contrast to whole-blood donation, which has an eight-week waiting period between donations. Along those lines, since platelet donation does temporarily remove whole-blood from your body, you must wait eight weeks after a whole blood donation to donate platelets.

Third, you may be required to have some additional tests done before becoming a donor for the first time. These tests are used to establish your platelet count, and also possibly to determine your compatibility with particular donors through an HLA (Human Leukocyte Antigen) test. The tests usually involve nothing more involved than the drawing of several tubes of blood. The human lymphocyte antigen system (HLA) is the group of genes in the human major histocompatibility complex (MHC) that encodes the cell-surface antigen-presenting proteins. ...

Vein scarring

Repeated platelet donations at short intervals will cause the venipuncture site to scar. While cosmetically, it is virtually invisible, the scarring also occurs on the vein itself, making it harder to insert a needle on future occasions. Anecdotal reports have said that rubbing Vitamin E oil (or the insides of a Vitamin E capsule) on the venipuncture site may reduce scarring. Tocopherol, or Vitamin E, is a fat-soluble vitamin in eight forms that is an important antioxidant. ...

It may be necessary to warn anybody outside of the blood center that needs to draw blood from that site that your vein may be somewhat tougher than normal. Failure to do so may result in the nurse thinking they have missed the vein, not realizing that the vein simply takes a little more pressure to stick.


The Haemonetics machine draws a large amount of blood in each cycle.

Usually 5-7 cycles per donation (draw: 15 min, return: 10 min). You can donate up to two platelet units during one donation (this is done with donors with a high count), and a unit of plasma can also be donated, at the center's discretion.


The Trima Automated Blood Collection System can collect two doses within two hours. The donor should have a platelet count of over 250×105/mm3. This unit also draws more suction than the Haemonetics and lacks an automated arm cuff. This means it requires a pretty fair-sized vein to support.

However, the Trima draws and returns blood in very small amounts more frequently than the Haemonetics, resulting in more than 100 cycles/unit (draw 40 sec, return 15 sec). This generally results in a lower pressure drop during the cycle since less blood is out of your body at any one time.

"Trima" can also perform the collection of platelets and red blood cells simultaneously.

COBE Spectra

This older unit is still in use in some blood centers. While it can perform a single-needle donation, the most common method with this machine is to draw with one needle, and return with the other, continuously drawing the blood through a centrifuge (instead of using cycles). For obvious reasons, the single needle Trima and Haemonetics machines are more popular, while the COBE Spectra is being phased out.

See also

Blood transfusion is the taking of blood or blood-based products from one individual and inserting them into the circulatory system of another. ... 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. ... A WWII-era poster encouraged American women to volunteer for the Red Cross as part of the war effort. ... Canadian Blood Services is a non-profit organization that manages the blood supply for Canada, and operates at arms length from the Government of Canada. ...

External links

Donation Centers

http://www.lifesouth.org/donorservices/donor_services2.htm (donation centers located in Florida, Georgia, and Alabama)

http://www.redcross.org/services/biomed/0,1082,0_554_,00.html (donation centers all over the US, including Alaska and Hawaii, and Puerto Rico)

http://www.cbccts.org/donating/automated.htm (Indiana and Ohio)

http://www.lifeshare.org/donation/apheresis.html (Louisiana, Texas)

http://www.lifeblood.org/donating/donating_platelets.htm (Tennessee, Arkansas, Mississippi)

http://www.kcblood.org/donating/donating_platelets.htm (Missouri, Kansas)

http://psbc.org/programs/platelets.htm (Washington)

http://www.nybloodcenter.org/index.jsp (New York)

http://www.unitedbloodservices.org/pheresis.html (California, Nevada, Utah, New Mexico, Arizona, Colorado, Texas, Oklahoma, Wyoming, Minnesota, North and South Dakota, Montana, Louisiana, Mississippi.... etc)

  Results from FactBites:
Delta Blood Bank (272 words)
Plateletpheresis (plate-let-fur-ee-sis) is a special blood donation process that utilizes special equipment, allowing you to give just one part of your blood - platelets - the cells that help stop bleeding.
With plateletpheresis, a small amount of blood is drawn from your arm into a blood cell separator.
While the blood is in the separator, the platelets are carefully removed by centrifugal force and the remaining parts of your blood, the plasma, red cells and white cells, are returned to you.
Plateletpheresis at AllExperts (2088 words)
Plateletpheresis (also called thrombapheresis or thrombocytapheresis) is the transfusion of platelets, the components of blood that are involved in hemostasis (blood clotting).
The earliest manual forms of plateletpheresis are done by the separation of platelets from multiple bags of whole blood collected from donors or blood sellers.
Modern automatic plateletpheresis allows the blood donor to give a portion of his platelets, while keeping his or her red blood cell and at least a portion of blood plasma.
  More results at FactBites »



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