الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 143 |  |  |
| | | from | 143 | | |
Abstract
Platelets are produced from fragmentation of bone marrow cells known as megakaryocytes. Normally, the platelet count is 150,000 to 400,000 per μl. Platelets have a life span of 5 to 9 days. Extra or reserve platelets are stored in the spleen and released at the time of need.
Platelets play a major role in hemostasis. This is achieved by formation of thrombi when damage to the endothelium of blood vessels occurs. Both increase or decrease in platelet count can cause life threatening consequences. Variable laboratory tests are used to assess platelet count as well as platelet function.
Platelet disorders lead to defects in primary hemostasis characterized by prolonged bleeding time, petechiae and purpura.
Thrombocytopenia is caused by either increased destruction or decreased production of platelets. Increased destruction can be caused by immune mechanism (e.g: immune thrombocytopenia, Gestational thrombocytopenia, post-transfusion purpura… etc) or increased consumption (e.g: Thrombotic thrombocytopenic purpura).
Functional disorders of platelets are rare and most of them are mild (e.g: vWD, Bernard-Soulier syndrome, Glanzmann thrombasthenia… etc).
Platelets are obtained by two different methods: platelet concentrates from whole blood or apheresis platelets and have very short half life, typically 5 days. Platelets are stored under constant agitation at 20-240C. The importance of ABO blood group system compatibility in platelet transfusion is a subject of ongoing debate.
Prophylactic use of platelet concentrates is possible in severe cases of thrombocytopenia and preoperatively. The need for platelet concentrates in the presence of thrombocytopenia or functional defects of platelets, depends on the presence or absence of coagulation disorders, ongoing treatments, as well as the clinical condition of the patient.
Like other blood components, platelet transfusions have achieved a high degree of safety as far as transmission of viral diseases is concerned. However, transfusion of platelet concentrates is accompanied by a high frequency of febrile and anaphylactoid reactions. In rare cases, recipients of platelet concentrates are threatened by severe reactions as septic complications due to bacterial contamination of platelet concentrates, transfusion-related acute lung injury and severe anaphylactic episodes