Platelets, or thrombocytes, are tiny blood cell fragments derived from large bone marrow cells called megakaryocytes. When circulating platelets encounter a damaged blood vessel, they clump together and form a platelet plug at the injury site. The platelet plug activates blood proteins called coagulation factors, which interact with the platelets to form a clot and arrest bleeding from the damaged blood vessel. Patients with a severely decreased platelet count, or thrombocytopenia, sometimes require platelet transfusions. A variety of medical conditions can cause thrombocytopenia, necessitating a platelet transfusion.
Massive Bleeding
Patients with high-volume bleeding may require a platelet transfusion to replenish the platelet supply. Bleeding depletes the platelet supply through direct loss and consumption of large numbers of platelets as the body attempts to halt the bleeding through clot formation. A normal platelet count is approximately 150,000 to 400,000 per microliter of blood, according to the National Library of Medicine encyclopedia MedlinePlus. A markedly low platelet count associated with a massive hemorrhage may contribute to ongoing bleeding. Continued bleeding due to a platelet deficiency proves most likely when the platelet count falls below 50,000 per microliter, reports the Southeastern Community Blood Center.
Dramatically Reduced Production of Blood Cells
Patients with aplastic anemia, leukemia and those receiving bone marrow-toxic chemotherapy drugs or preparing for a bone marrow transplant commonly exhibit bone marrow failure--profoundly reduced production of all blood cells. These patients typically exhibit severely diminished platelet counts and may require a platelet transfusion to prevent bleeding. The platelet level at which a platelet transfusion to prevent bleeding proves advisable varies according to the patient's diagnosis, explains the National Institutes of Health Consensus Development Conference Statement on Platelet Transfusion Therapy. In general, patients with a platelet count greater than 20,000 per microliter are unlikely to spontaneously bleed and usually don't require preventative platelet transfusions. The consensus statement notes that patients with impaired platelet production are more likely to require preventative platelet transfusions than patients with thrombocytopenia caused by increased platelet destruction.
Among adult patients with acute leukemia, the American Society of Clinical Oncology generally recommends a preventative platelet transfusion if the platelet count drops below 10,000 per microliter. Leukemia patients with complicating factors may require a platelet transfusion at a higher platelet count.
Brain and Eye Surgery Bleeding
Bleeding from small blood vessels, or microvascular bleeding, can prove dangerous in patients undergoing brain or eye surgery. Surgeons may prefer a preoperative platelet count of 100,000 per microliter or higher for patients undergoing these procedures to help reduce the risk for potentially damaging microvascular bleeding, explains the Southeastern Community Blood Center. Platelet transfusions may be used to raise a patient's platelet count in these circumstances.
References
- MedlinePlus: Platelet Count
- Southeastern Community Blood Center: Indications for Platelet Transfusion Therapy
- National Institutes of Health: Platelet Transfusion Therapy: National Institutes of Health Consensus Development Conference Statement
- American Society of Clinical Oncology: Platelet Transfusion for Patients With Cancer: Clinical Practice Guidelines of the American Society of Clinical Oncology
- "British Journal of Hematology"; Guidelines for the Use of Platelet Transfusions; British Committee for Standards in Haematology, Blood Transfusion Task Force; June 2003
