my notes--platelet guidelines

Platelet Transfusion Guidelines

Name: Platelets

Major Products Available:

Platelets (Random donor platelets - RDP)

Platelets Pooled

Platelets Pheresis (Single donor platelets - SDP)

These products can be leukoreduced, washed, and/or irradiated.

Description/Contents: RDP are separated from whole blood by differential centrifugation. SDP are harvested from a single donor by hemapheresis. One unit of RDP contains at least 5.5x10¹⁰ platelets, typically 7.5x10¹⁰ platelets. Pooled RDP are typically prepared from 4-6 units of RDP. One unit of SDP contains at least 3x10¹¹platelets, typically 4x10¹¹ platelets. Platelets are suspended in donor plasma, unless washed. Volume is specified on the label.

Indications:

• Prevention/treatment of non-surgical bleeding due to thrombocytopenia.

If possible, prior to transfusion the reason for thrombocytopenia should be established. When thrombocytopenia is caused by marrow failure, the following transfusion triggers are considered appropriate:

• If platelet count is <10,000/mL and no additional abnormalities exist.

• If platelet count is between 10,000 and 20,000/mL and coagulation abnormalities exist or there are extensive petechiae or ecchymoses.
• If the patient is bleeding at sites other than skin and platelet count is <40-50,000/m L.
• Patients with accelerated platelet destruction with significant bleeding (such as autoimmune thrombocytopenia or drug-induced thrombocytopenia).

The endpoint should be cessation of bleeding, since an increment in platelet count is not likely to be achieved. Prophylactic transfusion is not indicated in these disorders.

• Prior to surgical and major invasive procedures when the platelet count is <50,000/ mL.

During neurosurgical and ophthamologic procedures some authorities recommend that the platelet count be maintained between 70,000 and 100,000/mL.

• Bleeding with qualitative platelet defect documented by history and/or laboratory tests.

The cause should be identified and corrected, if possible, prior to surgery. Platelet transfusion is indicated only if the defect cannot be otherwise corrected: for example, a congenital platelet abnormality. Consultation with the blood bank physician is recommended in these situations.

• Diffuse microvascular bleeding after cardiopulmonary bypass or massive transfusion.
  

Platelet count and coagulation studies should be performed prior to the transfusion to guide subsequent therapy. During surgery on patients with quantitative or qualitative platelet defects, the adequacy of hemostasis in patients should be evaluated by the assessment of microvascular bleeding. 

Platelet transfusion should be avoided in thrombotic thrombocytopenic purpura, heparin-induced thrombocytopenia, and post-transfusion purpura, except in cases of life-threatening hemorrhage.

Dosage and administration: Compatibility testing is not required. Platelet concentrate products should be ABO identical where possible because platelet increments may be higher. If not possible, good clinical results are usually obtained with ABO mismatched platelets. In this case, transfusion of large quantities of ABO incompatible plasma may lead to a positive direct antiglobulin test and, rarely, clinically significant red cell destruction. Rh compatibility is important but not always possible. Post-exposure prophylaxis with anti-Rh immune globulin should be considered following Rh positive platelet product transfusions to Rh negative women who may have children in the future.

A typical platelet transfusion dose is 1 SDP or 4-5 pooled RDP. This should raise the platelet count of a typical 70 kg man approximately 30,000-50,000/mL. Platelet count increments after transfusion may be lower than expected in the presence of certain medications, fever, splenomegaly, infection, or alloimmunization to HLA or specific platelet antigens. Consult the Blood Bank/Transfusion Medicine physician or Hematologist in such cases.

Alternative Therapy: DDAVP (desmopressin) may improve the platelet functional defect in uremia. It also raises von Willebrand factor levels in mild-moderate von Willebrand's disease, which may improve platelet function. Pharmacologic agents such as aprotinin may reduce major surgical bleeding and thereby avoid the dilutional thrombocytopenia characteristic of massive transfusion. Some of these agents may also have a direct effect on improving platelet function.