Platelet Depletion Blood disorders such as essential thrombocytosis (a disease in which the body produces a surplus of platelets) and some forms of leukemia can produce excess platelets, also known as thrombocytes. Platelets are colorless cells that form blood clots to heal wounds and control bleeding. Adhering to torn blood vessels, they create a plug and slow the loss of blood. The apheresis machine removes excess platelets and returns the rest of the blood to the body. Reducing excess platelets helps prevent stroke and heart attack.