When bleeding from a wound suddenly occurs, the platelets gather at the wound and attempt to block the blood flow. The mineral calcium, vitamin K, and a protein called fibrinogen help the platelets to form a clot.A normal platelet count in a healthy person is between 150,000 and 400,000 per mm3 of blood. Normal platelet counts are not a guarantee of adequate function. In some states the platelets, while being adequate in number, are dysfunctional.By using a special method called platelet aphaeresis, whole blood is separated into components, and the platelets are removed. The clinical response to platelet transfusion can be assessed by measuring the increment in platelet concentration achieved in the patient's blood.The complications of platelet transfusion most frequently result from contaminating leukocytes, red cells, plasma proteins and microorganisms.