Platelets or thrombocytes are small, irregularly-shaped fragments of cells that are derived from megakaryocytes, which are stem cells. The average lifespan of a platelet is between 8 and 12 days. Platelets play a fundamental role in blood coagulation or clotting and are a natural source of growth factors. They circulate in the blood of mammals and are involved in hemostasis, which leads to the formation of blood clots. In a healthy adult, the normal range for a platelet count is 150,000 - 450,000 K/ul.
Indication
The indication for transfusion is if the patient has a platelet count below 30,000 K/ul or one that is below 100,000 K/ul if the patient is undergoing a surgical procedure. If there is massive hemorrhage or bleed, regardless of platelet count, a patient may be transfused with platelets to help stop the bleeding.
Types of Donors
Platelets may come from one donor or from several different donors. If a single donor is used, the entire collection is in one bag. Platelet donations that come from several donors are considered random platelets. These are normally pooled together into one bag before they are given to the patient. An anticoagulant is necessary to avoid the blood clotting in the bag.
Compatability
When possible, platelets should be ABO identical with the recipient when possible. That means the donated platelets should have the same exact blood type as the patient. Rh negative recipients should receive Rh negative platelets when possible, particularly when it is a woman of child bearing age. Consider giving Rhogam (Rh immune globulin) if Rh positive platelets should need to be administered to these females. Platelets of unmatched types may still be given in an emergency if that is all that is available but doing so leads to shortened platelet survival.
Dosing
A typical patient is given one bag of platelets at a time. That bag may contain a single donor pheresis or the platelets of between four and ten different individuals. If there are several donors, the bag of platelets is considered to be pooled random platelets. These will be given to treat patients with low platelet counts or to treat bleeding, this may be repeated to maintain target platelet count.
Response
The recipient should have their platelet count measured somewhere from ten minutes to three hours after transfusing. This is done to see if the transfusion was successful. Usually, you expect an adult platelet count should increase in increments of 10,000 per bag of platelets given. A child's platelet count will most likely increase more than 10,000 per bag. Response to platelet transfusion is adversely affected by fever, sepsis, enlarged spleens, severe bleeding, and certain drugs, i.e. amphotercin B In these cases, the platelet count may not elevate after transfusion at all.
Contraindications
Platelets transfusion should be administered to patients who have automimmune platelet disorders. These patients should only receive platelets in the case of a life threatening hemorrhage.
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