From the Guidelines
To increase the platelet count by 20,000/μL, a dose of 0.25 to 0.35 × 10¹¹ platelets per 10 kg body weight is recommended, which is approximately half of the standard unit of platelets. This recommendation is based on the most recent and highest quality study available, which suggests that 1 unit of platelets per 10 kg body weight will raise the platelet count by approximately 50,000/μL 1. Given that the desired increase is 20,000/μL, which is less than the expected increase from a standard unit, a partial unit might be sufficient. However, in clinical practice, platelets are generally transfused as complete units. The actual increase in platelet count should be assessed with a post-transfusion platelet count, typically performed 1 hour after transfusion. Factors that may reduce the expected increment include fever, sepsis, splenomegaly, DIC, certain medications, and immune-mediated platelet destruction. Platelets should be ABO-compatible when possible and transfused promptly after being obtained from the blood bank, as they have a short shelf life of only 5-7 days. Some studies suggest using a rough estimate of an absolute increment of 2,000/unit of PC or 10,000/transfusion of apheresis platelets to be equivalent to a CCI of 5,000 1. However, the most recent study provides a more precise calculation based on body weight and platelet dose 1. It is essential to note that the effectiveness of monitoring and acting on post-transfusion platelet counts has not been formally studied, but it is a consensus among experts that patients remain at risk of hemorrhagic events if the post-transfusion counts are still at or below the platelet value used to trigger the initial transfusion 1.
Some key points to consider when transfusing platelets include:
- The dose of platelets required to achieve a desired increase in platelet count
- The need for ABO-compatible platelets when possible
- The importance of assessing the actual increase in platelet count after transfusion
- The potential factors that may reduce the expected increment
- The short shelf life of platelets and the need for prompt transfusion after obtaining from the blood bank. The most recent study provides the most accurate and up-to-date information on the dose of platelets required to increase the platelet count by 20,000/μL 1.
From the Research
Platelet Transfusion Dose
To increase the platelet count by 20,000/µL, the required dose of platelets for a transfusion can be estimated based on the following evidence:
- A study published in 1995 2 suggests that each 1 x 10(11) platelets transfused will increase the blood platelet count approximately 10 x 10(9)/L per each square meter of patient body surface area.
- Based on this calculation, a dose of 3 x 10(11) platelets is estimated to increase the platelet count by approximately 20 x 10(9)/L (or 20,000/µL) for a patient with a body surface area of 2.0 m2.
- However, the same study notes that this dose may be inadequate to control bleeding in most thrombocytopenic adult patients, and recommends adjusting the dose based on body size.
- Another study published in 1998 3 found that high doses of platelets (6-8 x 10(11) platelets) led to a significantly better platelet increment (52 x 10(9)/L) compared to medium doses (4-6 x 10(11) platelets), which resulted in a platelet increment of 33 x 10(9)/L.
- The optimal dose of platelets for transfusion may vary depending on the patient's clinical status, body size, and other factors, and further research is needed to determine the most effective dose for increasing platelet count by 20,000/µL.
Key Considerations
Some key considerations when determining the required dose of platelets for transfusion include:
- Patient body size and surface area
- Pre-transfusion platelet count
- Clinical status and presence of bleeding or other complications
- Availability of platelet concentrates and donor exposure
- Potential risks and benefits of platelet transfusion, including refractoriness, hemolysis, acute lung injury, and bacterial sepsis 4