Editing Plateletpheresis (section)

==Platelet transfusion==
[[Platelet transfusion]]s are traditionally given to patients undergoing [[chemotherapy]] for [[leukemia]], [[multiple myeloma]], those with [[aplastic anemia]], [[AIDS]], hypersplenism, [[idiopathic thrombocytopenic purpura]] (ITP), [[sepsis]], bone marrow transplant, [[radiation treatment]], [[organ transplant]] or surgeries such as [[cardiopulmonary bypass]]. Platelet transfusions should be avoided in those with [[thrombotic thrombocytopenic purpura]] (TTP) because it can worsen neurologic symptoms and [[Acute kidney injury|acute renal failure]], presumably due to creation of new thrombi as the platelets are consumed. It should also be avoided in patients with [[heparin-induced thrombocytopenia]] (HIT) or [[disseminated intravascular coagulation]] (DIC).{{cn|date=December 2021}}

In adults, platelets are recommended in those who have levels less than 10,000/μL, or less than 20,000/μL if a [[central venous catheter]] is being placed, or less than 50,000/μL if a [[lumbar puncture]] or major surgery is required.<ref>{{cite journal|last1=Kaufman|first1=RM|last2=Djulbegovic|first2=B|last3=Gernsheimer|first3=T|last4=Kleinman|first4=S|last5=Tinmouth|first5=AT|last6=Capocelli|first6=KE|last7=Cipolle|first7=MD|last8=Cohn|first8=CS|last9=Fung|first9=MK|last10=Grossman|first10=BJ|last11=Mintz|first11=PD|last12=Sesok-Pizzini|first12=DA|last13=Shander|first13=A|last14=Stack|first14=GE|last15=Webert|first15=KE|last16=Weinstein|first16=R|last17=Welch|first17=BG|last18=Whitman|first18=GJ|last19=Wong|first19=EC|last20=Tobian|first20=AA|title=Platelet Transfusion: A Clinical Practice Guideline From the AABB|journal=Annals of Internal Medicine|date=11 November 2014|pmid=25383671|doi=10.7326/M14-1589|volume=162|issue=3|pages=205–13|s2cid=13276003 |doi-access=}}</ref>

===Whole blood platelets===
[[File:Platelets collected by using apheresis.jpg|thumb|right|Platelets collected by using [[apheresis]] at an [[American Red Cross]] donation center]]
Not all platelet transfusions use platelets collected by automated apheresis.  The platelets can also be separated from donations of [[whole blood]] collected in a traditional [[blood donation]], but there are several advantages to separating the platelets at the time of collection.  The first advantage is that the whole-blood platelets, sometimes called "random" platelets, from a single donation are not numerous enough for a dose to give to an adult patient.  They must be pooled from several donors to create a single transfusion, and this complicates processing and increases the risk of [[transfusion-transmitted infection|diseases]] that can be spread in transfused blood, such as [[human immunodeficiency virus]].{{Citation needed|date=July 2011}}

Collecting the platelets from a single donor also simplifies [[human leukocyte antigen]] (HLA) matching, which improves the chance of a successful transfusion.  Since it is time-consuming to find compatible donors for HLA-matched transfusions, collecting a full dose from a single donor is more practical than finding multiple compatible donors.{{cn|date=December 2021}}

Plateletpheresis products are also easier to test for bacterial contamination, a leading cause of transfusion-associated deaths.{{Citation needed|date=July 2011}}  Pooling of whole blood platelets is often done in an "open" system where the platelet containers are connected in a way that could expose the platelets to air, and pooled platelets must be transfused promptly so that any contamination does not have time to grow.{{cn|date=December 2021}}

Problems with apheresis include the expense of the equipment used for collection. Whole blood platelets also do not require any additional donor recruitment, as they can be made from blood donations that are also used for [[packed red blood cells]] and [[blood plasma|plasma]] components.{{cn|date=December 2021}}

===Thrombocytopenia due to underproduction===
Recipients in this category include those undergoing chemotherapy, those with [[myelophthisic anemia]], [[AIDS]], or with [[aplastic anemia]]. If indicated, transfusions (one thrombapheresis 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 and 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.{{cn|date=December 2021}}

===Immune thrombocytopenia===
Recipients in this category include those with idiopathic thrombocytopenic purpura 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. Platelet transfusion may be used in emergency bleeding situations where the platelets could be used by the body before the immune system destroys them.

===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 factor VIIa|recombinant human factor VIIa]]{{medcn|date=July 2021}} since the underlying cause are antibodies to platelet [[Glycoprotein IIb/IIIa|glycoproteins IIb/IIIa]].

===Cardiopulmonary bypass surgery===
[[Cardiopulmonary bypass surgery]] can result in destruction of a large proportion of the patient's platelets and may render the remaining viable platelets dysfunctional. The indications for transfusion in such patients is controversial. General guidelines recommend not transfusing patients prophylactically but only when they are bleeding excessively, while also giving desmopressin.{{cn|date=December 2021}}

===Drug-induced platelet dysfunction===
The most common of these is [[aspirin]], and its similar drug class, the [[NSAIDs]]. Other anti-platelet 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.