Page 485 - Hematology_ Basic Principles and Practice ( PDFDrive )

406 Part IV Disorders of Hematopoietic Cell Development

unrecognized. The ultimate benefits of definitive therapies such as treatment of serious hemorrhage should include correction of severe
transplantation or immunosuppression will be unrealized if the patient anemia and RBC transfusions.
succumbs to an early clinical catastrophe. A haphazard transfusion Modern transfusion practice has made platelets readily available
policy increases the risk of graft rejection after BM transplantation, and safe to administer. Other than cost and convenience, the major
but an overly conservative approach to transfusion can jeopardize problem related to platelet transfusions is the development of alloim-
the patient’s life and increase morbidity. Supportive management munization in the recipient. The life span of the transfused platelet
therefore requires meticulous attention to the daily problems that in the circulation is dramatically shortened by host antibodies, almost
occur as a consequence of pancytopenia and appreciation of their always directed to HLA-A and HLA-B antigens. Alloimmunization
impact on the ultimate possibilities for cure or amelioration of AA. is suggested by poor recovery of the 1-hour posttransfusion platelet
AA can be cured by replacement of stem cells, by BM transplantation, count and confirmed by finding specific HLA antibodies in serum.
and by immunosuppressive therapy. Androgens and hematopoietic Refractoriness can often be overcome by selection of HLA-matched
growth factors have secondary roles (see box on Treatment Algorithm donors. Alloimmunization can be prevented or delayed by the use of
in Aplastic Anemia). single-donor platelets rather than pooled platelets, and by physical
leukocyte depletion, by filtration or ultraviolet treatment of blood
Supportive Management products. Avoidance of platelet transfusions except when there is
active bleeding is another alternative to prevent alloimmunization,
but the dose relationship between exposure to different donors’
Bleeding platelets and the probability of developing refractoriness are not
clearly established.
Bleeding was historically a common symptom in AA, and death from Prophylactic transfusion of platelets is not standard but neverthe-
hemorrhage occurred frequently in the premodern era. Platelet less frequent in practice. The primary indication for platelet prophy-
transfusions have substantially improved survival in patients with this laxis is to prevent intracranial hemorrhage, but the risk of this
disease. Measurable correction of the platelet count by transfusion complication in the chronically thrombocytopenic patient, although
almost always alleviates the minor mucocutaneous bleeding common real, is low. Prophylactic platelet transfusions have not been shown
in thrombocytopenic patients. Major bleeding is usually not caused to alter patient survival. Nevertheless the beneficial effects of avoiding
by thrombocytopenia alone, and other explanations for massive bleeding complications and improving the quality of life justifies their
hemorrhage should be sought. The bleeding time improves after use. Although the 20,000 platelets/µL value has long been used to
erythrocyte transfusion in patients with anemia, and there is a strong trigger transfusion, many reports have suggested little difference in
inverse correlation between the hematocrit and bleeding. The the risk of bleeding over a wide range of platelet counts between 5000

Treatment Algorithm in Aplastic Anemia

Acquired aplastic anemia

Blood counts

Severe disease Moderate disease

Age Clinical status

Children-young adults Older adults TX-dependent Adequate
blood count

ATG + CSA
HLA typing ATG Observation

Sibling match No family donor Blood count Responders Non-responders
improvement
at 3-6 months
BMT ATG + CSA CSA; androgens

Non-responders Responders Non-responders

Allogeneic BMT; Follow for relapse, Allogeneic BMT;
androgens, 2nd IS late clonal disease androgens, 2nd IS
Algorithm-based selection of treatment for patients with aplastic anemia. ATG, antithymocyte globulin; BMT, bone marrow transplantation; CSA, cyclosporine A; HLA, human
leukocyte antigen; IS, immunosuppression; TX, treatment.