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20-September-2008 09:55:54 - Plateletpheresis A 250 ml bag of newly collected platelets. A 250 ml bag of newly collected platelets. Plateletpheresis also called thrombapheresis or thrombocytapheresis is the process of collecting platelets, the components of blood that are involved in hemostasis blood clotting. It can be a life-saving procedure in preventing or treating serious complications from bleeding and hemorrhage in patients who have disorders manifesting as thrombocytopenia low platelet count or platelet dysfunction. This process may also be used therapeutically to treat disorders resulting in extraordinarily high platelet counts such as Essential Thrombocytosis. Contents 1 Indications for transfusion 2 Expected platelet increase after transfusion 3 Platelet collection 3.1 Leukoreduction 3.2 Apheresis 4 Platelet donation 4.1 Haemonetics 4.2 Trima Gambro 4.3 COBE Gambro Spectra 4.4 Vein scarring 5 See also 6 References 7 External links Indications for transfusion Platelet transfusions are traditionally given to those undergoing chemotherapy for leukemia, those with aplastic anemia, AIDS, hypersplenism, ITP, sepsis, DIC, bone marrow transplant,radiation treatment, organ transplant or surgeries such as cardiopulmonary bypass. Platelet transfusions should be avoided in those with TTP-HUS because it can worsen neurologic symptoms and acute renal failure, presumably due to creation of new thrombi as the platelets are consumed. It should also be avoided in those with heparin-induced thrombocytopenia HIT.1 Thrombocytopenia due to underproduction. Patients in this category falls under those undergoing chemotherapy, those with myelophthisic marrow, AIDS, or with aplastic anemia. If indicated, transfusions one plateletpheresis concentrate should be given until recovery of platelet function, generally approximately twice weekly. Surgical bleeding due solely to thrombocytopenia occurs when platelets 50,000/µL while spontaneous bleeding occurs when platelets 10,000/µL. Thrombocytopenic patients can develop dry bleeding, that is, petechiae and ecchymoses only. They will not suffer fatal hemorrhagic events unless they first have extensive mucosal bleeding, or wet bleeding. Therefore, in those with no bleeding or only dry bleeding, the threshold for transfusion should be between 5,000 to 10,000/µL. A more conservative threshold of 20,000/µL should be used in those with a fever or other risk factors for bleeding. Those with active bleeding or prior to surgery should have a threshold of 50,000/µL. An unconfirmed, but helpful, way to determine whether a patient is recovering from chemotherapy-induced thrombocytopenia is to measure reticulated platelets, or young RNA-containing platelets, which signifies that the patient is starting to make new platelets. Immune thrombocytopenia. Patients in this category include those with ITP or drug-induced thrombocytopenia. Platelet transfusions are generally not recommended for this group of patients because the underlying cause involves antibodies that destroy platelets, therefore any newly transfused platelets will also be destroyed. More studies need to be done. Altered platelet functions. Disorders of platelet function can be congenital or acquired. Most of these disorders are mild and may respond to therapy with desmopressin dDAVP. Transfusion is not necessarily required. However, with some more severe disorders such as Glanzmann thrombasthenia, transfusions with large amount of platelets may be needed. The number of transfusions may be reduced if these patients are given recombinant human factor VIIa since the underlying cause are antibodies to platelet glycoproteins IIb/IIIa. Cardiopulmonary bypass surgery. This surgery can result in destruction of a large proportion of the patient's platelets and may render the remaining viable platelets to be dysfunctional. The indications for transfusion in such patients is controversial. General guidelines recommends not transfusing patients prophylactically but only when they are bleeding excessively, while also giving desmopressin. Drug-induced platelet dysfunction. The most common of these is aspirin, and its similar drug class, the NSAIDs. Other antiplatelet drugs are commonly prescribed for patients with acute coronary syndromes such as clopidogrel and ticlopidine. When surgery is undertaken following the administration of these drugs, bleeding can be serious. Transfusion under these circumstances is not clear-cut and one has to use clinical judgment in these cases. Expected platelet increase after transfusion Platelet count increase as well as platelet survival after transfusion is related to the dose of platelets infused and to the patient's body surface area BSA. Usually these values are less than what would be expected. Corrected platelet count increment CCI = platelet increment at one hr x BSA m2 / # platelets infused x 1011 Expected platelet increase per μL = platelets infused x CCI / BSA m2 The theoretical value of the CCI is 20,000/μL but clinically, the value is more close to 10,000/μL. If the CCI is less than 5,000/μL, patients are said to have refractoriness to platelet transfusion. Platelet collection 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. Modern automatic plateletpheresis allows the blood donor to give a portion of his platelets, while keeping his or her red blood cells 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. Most donors will donate a single or double unit, however the occurrence of triples has been increasing as more suitable donors are recruited. Because platelets have a life-span of just 5 days, more platelet donors are always needed. Some centers are experimenting with 7 day platelets, but this requires additional testing and the lack of any preservative solutions means that the product is far more effective when fresh. 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. Leukoreduction 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. 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. 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 5×106 white blood cells. 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. Platelets are the clotting factor of your blood, and when donated, frequently go to cancer patients, because due to chemotherapy many cancer patients are unable to generate enough platelets of their own. 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 mobile blood drives. Each country has its own rules to protect the safety of both donor and recipient. In a typical set of rules, a platelet donor must weigh at least 50 kg 110 lb and have a platelet count of at least 150 x 109/L 150,000 platelets per mm³.1 One unit has about 3×1011 platelets. Therefore, it takes 2 liters of blood having a platelet count of 150,000/mm³ to produce one unit of platelets. Some regular donors have higher platelet counts over 300,000/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. Platelet donation After a mini-physical, the donor is taken into the donation room and sits in a chair next to the machine. The tech cleans one arm with iodine, or other disinfectant, and inserts the catheter into a vein. 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. The donor may have the option of donating a unit of plasma with the platelets, if he chooses. The donor's blood is pulled into the machine and returned to the donor usually about 6-8 times, accounting for the length of the donation. Occasional side effects of the donation of platelets include tingling, chills, slight nausea, bruising, fatigue, and dizziness. Frequently while donating the lips may begin to tingle; a supply of calcium antacid tablets is usually kept close by because the anticoagulant works by binding to the calcium in the blood. Since calcium is used in the operation of the nervous system, nerve-ending-dense areas such as the lips are susceptible to the tingling. Usually chewing a handful of antacid tablets will raise calcium levels and relieve the tingling. Bruising may also occur. Fatigue and dizziness are generally not as common after donating platelets as it is after donating blood because the red blood cells are returned to the donor. Aside from the procedure, donating platelets is different from donating blood in a few ways. Firstly, the donor must not take aspirin for anywhere from 36 to 72 hours prior to donation. Guidelines vary by blood center. The reason for this is that aspirin can prevent platelets from adhering. Some blood centers also prohibit the taking of any NSAID non-steroidal-anti-inflammatory-drug for 36 hours prior. Other medications such as clopidgrel Plavix may also affect platelet function and may affect donor eligibility. Secondly, one is generally allowed to donate platelets anywhere from every 3-28 days. This is a stark contrast to whole-blood donation, which has an eight-week or longer waiting period between donations. Along those lines, since platelet donation does temporarily remove whole-blood from the body, it may become necessary to wait eight weeks after a whole blood donation to donate platelets. In the US, a donor is only allowed to donate 24 times each year and may not lose more red blood cells or plasma in a year than they would from the maximum allowable number of whole blood donations. Thirdly, additional tests may be required before becoming a donor for the first time. These tests are used to establish a platelet count, and also possibly to determine the donor's compatibility with particular recipients through an HLA Human Leukocyte Antigen test. The tests usually involve nothing more involved than the drawing of several tubes of blood. Haemonetics The Haemonetics machine draws a large amount of blood in each cycle. Usually 5-7 cycles per donation approx. 10 min per cycle. Up to two platelet units can be obtained 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. Trima Gambro The Trima Automated Blood Collection System can collect up to three units within two hours. 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 unless a portable blood pressure cuff is available. The Trima collection system has incorporated a leukocyte reduction cone as part of the disposable kit. Use of this device routinely produce platelet concentrates with white blood cell counts of less than 1×106 per product. However, the Trima draws and returns blood in very small amounts compared to 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 the body at any one time. Trima can also perform the collection of platelets, plasma and red blood cells simultaneously. COBE Gambro 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. 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.citation needed It may be necessary for the donor to warn anybody who needs to draw blood from a scarred site that the vein may be somewhat tougher than normal. Failure to do so may result in the tech thinking they have missed the vein, not realizing that the vein simply may take a little more pressure to stick.citation needed See also Blood transfusion Blood donation American Red Cross Canadian Blood Services References ^ Criteria for acceptance of donors. Retrieved on 2008-02-25. Stroncek DF, Rebulla P 2007. Platelet transfusions. Lancet 370 9585: 427-38. doi:10.1016/S0140-67360761198-2. PMID 17679020. Circular of Information for Blood Products, page 32 page 35 of the PDF External links Apheresis News v d e Transfusion medicine General concepts Apheresis Plasmapheresis, Plateletpheresis, Leukapheresis - Blood transfusion - Coombs test - Cross-matching - Exchange transfusion - International Society of Blood Transfusion - Intraoperative blood salvage - ISBT 128 - Transfusion reactions Human blood group systems - Blood type ABO - Chido-Rodgers - Colton - Cromer - Diego - Dombrock - Duffy - Gerbich - GIL - Hh - Ii - Indian - JMH - Kell Xk - Kidd - Knops - LW - Lewis - Lutheran - MNS - OK - P - Raph - Rh - Scianna - T-Tn - Xg - Yt - Other Blood products Blood donation - Blood substitutes - Cryoprecipitate - Platelets - Plasma - Red blood cells - Whole blood Retrieved from http://en..org/wiki/Plateletpheresis Categories: Transfusion medicineHidden categories: All articles with statements | Articles with statements since May 2007 Views Article Discussion this page History Personal tools Log in / create account Navigation Main page Contents Featured content Current events Random article Search Go Search Interaction Community portal Recent changes Contact Donate to Help Toolbox What links here Related changes Upload file Special pages Printable version Permanent link Cite this page Languages Polski This page was last modified on 7 August 2008, at 17:17
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