Proposed guidelines for platelet transfusion

The guidelines that follow are proposed to support physicians in their clinical decisions related to the appropriate use of platelet products. They are not intended to provide a rigid prescription for care and do not replace the need to consult with an expert in transfusion medicine. The decision to transfuse platelets should be based on the judgment of the attending physician after careful review of the patient’s condition and clinical situation. The goal is to optimize patient outcomes and to ensure appropriate use of the allogeneic (donor) blood supply. These guidelines apply to platelet transfusion in adults and are generally applicable to children with the exception of neonates.

These guidelines are periodically updated and are available electronically on the British Columbia Provincial Blood Coordinating Office web site (www.bloodlink.bc.ca). Prescribing physicians should refer to the most current version of these guidelines.

General considerations

• Informed consent is required for the transfusion of platelets.
• The cause of thrombocytopenia must be established prior to platelet transfusion. This is critical as platelet transfusions are not indicated in all cases and may be contraindicated for certain conditions, such as heparin-induced thrombocytopenia and thrombotic thrombocytopenic purpura/hemolytic uremic syndrome.
• Once the cause of thrombocytopenia has been established, the decision to transfuse platelets should not be based solely on the patient’s platelet count. The decision to transfuse should be supported by the need to prevent or treat bleeding.
• Platelet transfusion should be given only after the risks associated with transfusion have been considered and only when the benefits outweigh the risks. Risks include the general risks of transfusion. The physician should also keep in mind that the risks of bacterial contamination (1:10 000) and alloimmunization to platelets are increased with platelet transfusion.[1] 
• Strategies should be undertaken to minimize the need to transfuse platelets. For example:
- Investigate, diagnose, and treat previously recognized thrombocytopenia.
- Discontinue anticoagulants and antiplatelet agents before planned surgery.
- Use adjunctive agents in specific situations (e.g., desmopressin, antifibrinolytics).
• Ensure that all other coagulation parameters are checked as well. 
• When platelets are transfused, the reasons for the transfusion should be clearly and accurately recorded in the patient’s chart and in any documentation used in ordering or administering platelets.

Platelet products

Platelets have a shelf life of 5 days and are stored at 20°C to 24°C with continuous gentle agitation.[2] Because platelets have a limited shelf life, platelet products are often in short supply. Most hospitals do not routinely stock platelets, so the transfusion medicine laboratory should be forewarned, whenever possible, of anticipated platelet requirements. Different platelet products exist, of which the most commonly used are as follows:

• Random-donor platelet unit: Each platelet unit contains at least 55 x 109 platelets suspended in 40 to 70 mL of plasma.[2,3] The typical platelet prescription is 10 mL/kg to a maximum of five random-donor platelet units. Note that each platelet unit is derived from a different donor.

• Single-donor apheresis platelet unit: Each apheresis platelet unit contains at least 300 x 109 platelets suspended in 200 to 400 mL of plasma and is derived from a single donor.[2,3] Apheresis platelet units are preferred when a patient becomes refractory to random-donor platelet units, though the use of single-donor apheresis platelet units as first-line platelet products is increasing.

Response to platelet products

Typically one unit of random-donor platelets should increase the platelet count of a 70 kg adult by 5 x 109/L.[3] Response to platelet transfusions should be assessed by obtaining a platelet count 15 minutes to 1 hour posttransfusion and calculating the corrected count increment (CCI) as shown in the Figure .

A CCI of >7.5 at 1 hour after transfusion or >4.5 at 20 to 24 hours after transfusion is considered acceptable. Platelet refractoriness is defined as the failure to achieve an expected CCI after two consecutive transfusion episodes.[4] Patients who are refractory should be assessed further by a transfusion medicine specialist or hematologist.

 Threshold and target platelet levels in the prevention of bleeding

As a general guide, the platelet count thresholds shown in the should in the Table be used for considering platelet transfusion.[4,5] Serious spontaneous bleeding is unlikely to occur at platelet counts >10 x 109/L. More specific recommendations are presented in the following sections.

 For patients undergoing cardiopulmonary bypass surgery

The pathophysiology of platelet dysfunction in cardiopulmonary bypass (CPB) surgery has not been elucidated. Platelet-related bleeding includes microvascular bleeding as indicated by continued oozing from surgical incisions and venous cannulation sites. The platelet count following CPB gives no indication of platelet function. Thus, platelet transfusion may be considered in patients who are experiencing excessive postoperative bleeding and in whom a surgical cause has been excluded. Consideration for transfusion should also be given to those patients who have recently received antiplatelet agents. Intraoperatively, autologous platelet harvest may be used. There is no role for prophylactic platelet transfusion in CPB.[4]

For patients with platelet dysfunction

Acquired causes of platelet dysfunction include the use of antiplatelet agents (e.g., ASA, clopidogrel) and renal disease. The platelet count is less useful in these situations and the decision to transfuse should be based on clinical circumstances. The following recommendations[4] should be implemented in order to avoid platelet transfusion if possible:

• Discontinue drugs with antiplatelet activity.
• Consider the use of desmopressin in patients taking ASA, as well as patients with uremia and other congenital and acquired causes of platelet dysfunction.
• Correct the hematocrit to >0.30 in patients with renal failure; consider the use of desmopressin and dialysis, which also have hemostatic benefits in this situation.
• Use platelet transfusions where the above methods are inappropriate or ineffective.
Patients with congenital platelet dysfunction must be managed in consultation with a hematologist.

 For patients undergoing surgery and invasive procedures

Expert consensus and retrospective case series suggest that a platelet count of >50 x 109/L is sufficient for most invasive procedures, including gastroscopy and biopsy, insertion of indwelling lines, transbronchial biopsy, liver biopsy, laparotomy, or similar procedures.[4,6,7] Platelet counts >100 x 109/L are recommended for neurosurgery or ocular surgery.[4]

For adults and children, most experts recommend platelet counts of >50 x 109/L prior to lumbar puncture as platelet counts <20 x 109/L have been associated with increased risk of hematoma or traumatic tap. No clear minimum platelet count has been identified for the insertion of epidural catheters, with published recommendations ranging from >50 x 80 x 109/L.[4,10,11]

Vaginal delivery can be performed safely with maternal platelet counts >50 x 109/L,[12] as hemostasis after placental separation is largely mechanical.

Bone marrow biopsy can be performed safely without platelet support if adequate surface pressure is applied.[4]

Posttransfusion platelet counts should be obtained before any invasive procedure. Platelets should be available for transfusion if bleeding complications arise.

 For critically ill patients with thrombocytopenia

No specific data exist regarding transfusion thresholds in the critically ill. The following recommendations are extrapolated from data in patients with acute leukemia. For patients who are critically ill with fever, sepsis, or coagulopathy, the platelet count should be maintained above 20 x 109/L. If there is significant bleeding, the platelet count should be maintained above 50 x 109/L.

 For patients with thrombocytopenia due to chronic marrow failure

The role of prophylactic platelet transfusion in patients with chronic stable thrombocytopenia due to myelodysplastic syndrome or aplastic anemia is unclear, as many patients do not experience serious hemorrhagic complications with platelet counts <5 x 10 x 109/L. Long-term prophylactic platelet transfusion is associated with transfusion risks, including alloimmunization. Maintaining a platelet count of >10 x 109/L in patients without other risk factors such as fever or coagulopathy is considered safe. Maintaining a lower threshold of 5 x 109/L or withholding prophylactic transfusion may be appropriate in selected stable patients. Hemorrhage should be treated with platelet transfusion.[4]

 For patients with leukemia or undergoing hematopoietic stem cell transplantation

Patients with acute leukemia (excluding acute promyelocytic leukemia) commonly require platelet transfusion support throughout their treatment course. Several studies have provided evidence that the threshold for prophylactic platelet transfusion can be lowered to 10 x 109/L.[4,13-15] This threshold is similar for hematopoietic stem cell transplantation. If the patient has fever, sepsis, disseminated intravascular coagulopathy, or minor bleeding, the platelet count should be maintained above 20 x 109/L.[4,14,16]

Though there are no specific studies for patients with acute promyelocytic leukemia, patients with this form of leukemia who have a concomitant coagulopathy should receive prophylactic platelet transfusion to maintain a platelet count >20 x 109/L.[4]

 For patients with acute blood loss resulting from trauma

A decrease in the platelet count to 50 x 109/L is expected when red cell concentrates equivalent to two blood volumes have been transfused. In patients with acute bleeding, the platelet count should be maintained above 50 x 109/L.[4,17] If injuries include multiple trauma or CNS injury, published recommendations suggest a target platelet count of 100 x 109/L.[4,18] In practice, however, local experience suggests that a count of 75 x 109/L as a target is more realistically achievable in the context of finite platelet resources.

 For patients with immune thrombocytopenic purpura

Platelet transfusions are often ineffective in immune thrombocytopenic purpura (ITP) and should be reserved for patients with life- or limb-threatening bleeding, in which case platelets should be maintained above 50 x 109/L. Patients with ITP with a platelet count <10 x 109/L should be transfused only in the setting of serious bleeding. In the rare circumstances when platelet transfusion is required in the management of ITP, other therapies such as corticosteroids and/or intravenous immunoglobulin should be given at the same time to enhance platelet survival.[4]

Contraindications

Platelet transfusions are contraindicated in thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS) and heparin-induced thrombocytopenia (HIT) unless there is life- or limb-threatening hemorrhage. Platelet transfusions have been associated with exacerbation of TTP/HUS and arterial thrombosis in HIT.[4]

Competing interests
None declared.

Table. Platelet count thresholds for platelet transfusion.

Figure. Corrected count increment (CCI) calculation.

Yulia Lin, MD, FRCPC, Lynda M. Foltz, MD, FRCPC

Drs Lin and Foltz are senior hematology residents at the University of British Columbia. These guidelines were commissioned by the British Columbia Transfusion Medicine Advisory Group (TMAG). TMAG is a technical, medical, and scientific advisory body to the Ministry of Health in guiding the development of blood program–related policies in British Columbia.