)One can get a clue as to whether bleeding is due to a platelet disorder or a coagulation factor disorder by the characteristics and location of the bleeding. : 815, Table 39-4  All of the following suggest platelet bleeding, not coagulation bleeding: the bleeding from a skin cut such as a razor nick is prompt and excessive, but can be controlled by pressure; spontaneous bleeding into the skin which causes a purplish stain named by its size: petechiae, purpura, ecchymoses; bleeding into mucous membranes causing bleeding gums, nose bleed, and gastrointestinal bleeding; menorrhagia; and intraretinal and intracranial bleeding. Excessive numbers of platelets, and/or normal platelets responding to abnormal vessel walls, can result in venous thrombosis and arterial thrombosis. The symptoms depend on the site of thrombosis. Tests of function
Bleeding time
Bleeding time was first developed as a test of platelet function by Duke in 1910. Dukes test measured the time taken for bleeding to stop from a standardized wound in the ear lobe which was blotted every 30 seconds. The normal time for bleeding to stop was less than 3 minutes. More modern techniques are now used. A normal bleeding time reflects sufficient platelet numbers and function, plus normal microvasculature. Multiple electrode aggregometry
In multiple electrode aggregometry, anticoagulated whole blood is mixed with saline and a platelet agonist in a single-use cuvette with two pairs of electrodes. The increase in impedance between the electrodes as platelets aggregate onto them, is measured and visualized as a curve.
Oral agents
Aspirin
Clopidogrel
Cilostazol
Ticlopidine
Ticagrelor
Prasugrel

Drugs that stimulate platelet production
Thrombopoietin mimetics
Desmopressin
Factor VIIa

Intravenous agents
Abciximab
Eptifibatide
Tirofiban
Others: oprelvekin, romiplostim, eltrombopag, argatroban

Therapy with platelets
Transfusion
Indications
Platelet transfusion is most frequently used to correct unusually low platelet counts, either to prevent spontaneous bleeding (typically at counts below 10×109/L) or in anticipation of medical procedures that will necessarily involve some bleeding. For example, in patients undergoing surgery, a level below 50×109/L is associated with abnormal surgical bleeding, and regional anaesthetic procedures such as epidurals are avoided for levels below 80×109/L. Platelets may also be transfused when the platelet count is normal but the platelets are dysfunctional, such as when an individual is taking aspirin or clopidogrel. Finally, platelets may be transfused as part of a massive transfusion protocol, in which the three major blood components (red blood cells, plasma, and platelets) are transfused to address severe hemorrhage. Platelet transfusion is contraindicated in thrombotic thrombocytopenic purpura (TTP), as it fuels the coagulopathy. Collection
Platelets are either isolated from collected units of whole blood and pooled to make a therapeutic dose, or collected by platelet apheresis: blood is taken from the donor, passed through a device which removes the platelets, and the remainder is returned to the donor in a closed loop. The industry standard is for platelets to be tested for bacteria before transfusion to avoid septic reactions, which can be fatal.