Blood is composed of a mixture of cells, suspended in a fluid called plasma. Red Cells carry oxygen around the body to the organs and tissue. White Cells fight 'invaders' such as harmful bacteria and help prevent infection. Plasma is the liquid part of blood. It contains proteins, salts and 'clotting factors' that help to prevent or stop bleeding.
Platelets are very small fragments of cells.
Platelets work with the clotting factors in plasma to form a mesh or 'plug' to stop or prevent bleeding . When a patient undergoes chemotherapy or radiotherapy to treat cancer or leukaemia, that treatment can destroy the patient's bone marrow. Bone marrow is the 'orchard' within the bones where blood cells form. Until the bone marrow recovers, the patient will be at risk of severe bleeding due to a lack of platelets in his or her bloodstream. During this recovery period, which may take several weeks the patient may need to receive platelet transfusions to maintain satisfactory numbers of platelets in circulation, or to stop actual bleeding.