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One common definition of thrombocytopenia requiring emergency treatment is a platelet count below 50,000/μL. [5] Thrombocytopenia can be contrasted with the conditions associated with an abnormally high level of platelets in the blood – thrombocythemia (when the cause is unknown), and thrombocytosis (when the cause is known). [6] [7]
Unmatched platelets, however, are often used due to the unavailability of matched platelets. [3] They are given by injection into a vein. [4] Side effects can include allergic reactions such as anaphylaxis, infection, and lung injury. [2] Bacterial infections are relatively more common with platelets as they are stored at warmer temperatures. [2]
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 10 9 /L (150,000 platelets per mm³). [2] One unit has greater than 3×10 11 platelets. Therefore, it takes 2 liters of blood having a platelet count of 150,000/mm³ to produce one unit of platelets.
Two giant platelets (stained purple) are visible in this image from a light microscope (40×) from a peripheral blood smear surrounded by red blood cells. One normal platelet can be seen in the upper left side of the image (purple) and is significantly smaller in size than the red blood cells (stained pink). Specialty: Hematology
Thrombotic thrombocytopenic purpura (TTP) is a blood disorder that results in blood clots forming in small blood vessels throughout the body. [2] This results in a low platelet count, low red blood cells due to their breakdown, and often kidney, heart, and brain dysfunction. [1]
Reactive thrombocythemia is the most common cause of a high platelet count. It accounts for 88% to 97% of thrombocythemia cases in adults, and near 100% in children. In adults, acute infection, tissue damage, chronic inflammation and malignancy are the common causes of reactive thrombocythemia. Usually, one or more of these conditions is ...
EDTA-dependent agglutination. In some individuals, clinically insignificant antibodies may cause in vitro agglutination of platelets. As a result of platelet clumping, platelet counts reported by automated counters may be much lower than the actual count in the blood because these devices cannot differentiate platelet clumps from individual cells.
Post-transfusion purpura (PTP) is a delayed adverse reaction to a blood transfusion or platelet transfusion that occurs when the body has produced alloantibodies to the allogeneic transfused platelets' antigens. These alloantibodies destroy the patient's platelets leading to thrombocytopenia, a rapid decline in platelet count. [1]