Triggers for prophylactic use of platelet transfusions and optimal platelet dosing in thrombocytopenic dogs and cats

Prophylactic platelet transfusions are frequently given to human patients with hypoproliferative thrombocytopenia at a trigger of 10,000/muL in the absence of other risk factors for spontaneous bleeding, and at 20,000/muL in the presence of such factors. The goal for prophylactic transfusion before surgery is to raise the platelet count to 50,000 to 100,000/muL, although surgery has been performed at lower platelet counts without major bleeding. Prophylactic transfusion against spontaneous bleeding is not recommended in disorders of platelet consumption and destruction. Platelet transfusion is performed much less frequently in dogs and cats; thus, firm recommendations are difficult. If an animal can be closely observed for major bleeding and if there is the ability to provide a prompt transfusion, transfusing once bleeding begins is advocated, because this reduces the number of transfusions required. Otherwise, prophylactic transfusion is recommended, applying the triggers recommended for people to dogs and lowering the triggers by 50% for cats. Platelet counts are imprecise at low values and must always be interpreted in conjunction with clinical signs. A dose of 1 unit of platelet-rich plasma or platelet concentrate per 10 kg is recommended, which raises the platelet count by a maximum of 40,000/muL and may be required approximately every 3 days. If fresh whole blood is used, a rule of thumb is to transfuse 10 mL/kg, which raises the platelet count by a maximum of 10,000/muL; transfusions on a daily basis or every other day may be required.