Rationale:

• Platelet transfusions may be used to treat hemorrhage in patients with thrombocytopenia.
• Decisions regarding the use of platelet transfusions must be based on an assessment of risk vs. benefit.
• Risks associated with platelet transfusions include alloimmunization, transmission of infection, allergic reactions, and transfusion-related acute lung injury.
• Potential benefits of platelet transfusions include reducing the morbidity associated with minor hemorrhage and reducing the morbidity and mortality resulting from major hemorrhage.

Evidence:

• A protocol for aggressive management of children with dengue shock syndrome was initiated in January 2000, and outcomes (duration of ventilation, pediatric ICU stay, incidence of ARDS, and ICU and hospital mortality) were compared before and after initiation of the protocol. The investigators found that transfusion of platelets based on platelet counts alone was not beneficial (103).
• Of 114 patients with severe dengue viral infections seen in Malaysia, 24 had severe hemorrhage, and 92 had no hemorrhage. Platelet counts were not predictive of bleeding. Duration of shock (OR, 2.1) and low-normal hematocrit at the time of shock (OR, 0.7) were risk factors for severe hemorrhage (104).
• A prospective study of children with dengue and severe thrombocytopenia found that platelet infusions did not alter outcome when significant bleeding was not present (105).
• The British Society for Haematology has provided guidance that concurs with the Consensus Conference on Platelet Transfusion (106) and the guidelines of the American Society of Clinical Oncology (107).
• According to the American Society of Clinical Oncology guidelines, a threshold of 10 × 10⁹/L is as safe for patients with additional risk factors as higher levels. Risk factors include sepsis, concurrent use of antibiotics, and other abnormalities of hemostasis (107).
• According to the Consensus Conference on Platelet Transfusion, a threshold of 5 × 10⁹/L may be appropriate for patients without any risk factors if there are concerns that alloimmunization could lead to platelet refractoriness. Accurate counting of low numbers of platelets may create difficulties when trying to reduce the threshold to <10 × 10⁹/L (106).

Comments:

• One adult therapeutic dose should increase the platelet level by at least 20 × 10⁹/L, provided the patient is not refractory.
• When platelets are used therapeutically to treat active bleeding, a larger dose may be indicated. The dose and frequency of administration depends on the individual circumstances, and it is not possible to give general advice.
• There is no consensus on a target platelet count, but aiming to maintain the platelet count >50 × 10⁹/L, as in massive blood loss, is reasonable (106).