A. Definition of thrombocytopenia
Significant thrombocytopenia (platelet count <100,000/pL) results in an increased risk of mucosal, skin, and central nervous system bleeding. The risk of bleeding is increased with coincident coagulation factor deficiencies, platelet dysfunction, mucositis, high peripheral blood blast count, fever, recent surgery, sepsis, or other causes of increased platelet turnover.
B. Symptoms of thrombocytopenia
When thrombocytopenia develops gradually, there may be few symptoms or signs. Common symptoms of thrombocytopenia include petechiae, epistaxis, gastrointestinal bleeding, and other mucosal bleeding. More serious bleeding can occur in the central nervous system and can be indicated by retinal hemorrhages.
C. Specific risks of platelet transfusion
The major risks of repeated platelet transfusions are CMV infection, platelet alloimmunization, and sepsis.
Rarely, in very small patients, there is a risk of volume overload when platelet transfusions are infused over a short period of time. The hemoglobin level after platelet transfusion is often lowered because of the fluid shifts. Volume reduction of platelet concentrates is not recommended, as such manipulation will adversely affect platelet function.
D. Options for the correction of thrombocytopenia
Platelet concentrates—AS-1 (Nutricel) or AS-3 (Adsol)— are used as additive solutions to the anticoagulant. Each platelet concentrate unit is approximately 60 mL.
Single-donor platelet apheresis packs are strongly recommended. One unit equals approximately 6 units of random-donor platelets. The units can be split for more efficient use of blood bank resources.
Washed platelet concentrates are not recommended unless the patient has severe allergic reactions.
Discourage directed donations from first-degree relatives. Transfusion may sensitize the child and interfere with an allogeneic bone marrow transplant. It is mandatory if directed donations from relatives are used that the blood be irradiated to prevent graft-versus-host disease.
E. Indications for platelet transfusion
The determination of a thrombocytopenic patient's need for platelet transfusion includes, in addition to the current platelet count and the rate of decrease of the platelet count, an assessment of concomitant factors that may increase the patient's risk of bleeding. The threshold for platelet transfusion may be lower in patients with any of these factors. General guidelines for platelet transfusion are the following.
Any child with a platelet count < 10,000/uL should be given a transfusion.
Children with acute promyelocytic leukemia or acute monocytic leukemia during induction treatment should be given a transfusion to maintain the platelet count above 20,000/uL. Patients with acute lymphoblastic leukemia during induction should have their platelet count kept > 15,000/uL.
Children with brain tumors should have their platelet count maintained > 30,000/uL during radiation therapy and the early phase of chemotherapy.
A child requiring surgery should have a platelet count >50,000/uL but > 100,000/uL for surgery of the eye or brain.
Children requiring a lumbar puncture should have a platelet count > 30,000/uL.
A child requiring an intramuscular injection should have a platelet count > 20,000/uL.
Any child with bleeding, in spite of a normal prothrombin time, partial thromboplastin, and fibrinogen level, whose platelet count is < 60,000/uL should be given a transfusion.
These recommendations are clinically reasonable but not in every circumstance supported by data.
F. Dose of platelet transfusion
Four units of platelet concentrates/m2 or 1 unit/7.5 kg should increase the platelet count by 50,000/uL by 60 minutes after transfusion.
In the actively bleeding patient, attempt to increase the platelet count by at least 40,000/uL.
It is preferable to use Rh-matched platelet units for females; ABO compatibility is recommended for all patients. If using single-donor apheresed platelets with an anti-A or anti-B titer > 1:64 for an A, B, or AB recipient, remove the plasma.
G. Platelet refractoriness
One definition of platelet refractoriness is a post-transfusion increment of < 5000/uL/unit of platelet concentrate/ m2 transfused when measured at 15-60 minutes after transfusion and recurring on more than one occasion.
Treatment options for platelet refractoriness
a. Try treatment with platelet units stored for less than 24
b. Try human leukocyte antigen (HLA)-matched single-
c. Try cross-matching compatible platelets.
d. Intravenous immunoglobulins are unlikely to be of benefit. If tried, the dose of intravenous immunoglobulin is
400 mg/kg/day before the platelet transfusion for up to
9 days. Transfuse the child with platelet concentrates
daily until a safe platelet count is achieved.
e. Consider massive transfusion with random-donor
platelets (to adsorb the antibodies) if the patient is
bleeding seriously and all other therapies have failed.
f. Consider a trial of vinblastine-loaded platelets.
g. Consider a trial of plasmapheresis with immunoadsorption onto staphylococcal protein A column.