Yesterday we went over a case of pancytopenia in an elderly woman, found to have severely hypocellular bone marrow consistent with a diagnosis of aplastic anemia. Below are the main teaching points from the discussion:
Prophylactic Platelets Transfusion: To prevent spontaneous bleeding in high risk patients.
- Transfuse if platelets <10
- Avoid prophylactic platelet transfusion in patients with consumptive platelet disorders like DIC or TTP unless they are undergoing invasive procedures requiring platelet transfusion
- Consider transfusing at a higher platelet number if:
- patient had a previous spontaneous bleed at a certain platelet count above 10
- coexisting inflammation, infection, and fever (some sources suggest a platelet goal of 20-30 for septic patients)
Platelet Transfusion for Bleeding Patients: To aid in hemostasis
- Transfuse with a platelet goal of >50
- If there is CNS bleeding, transfuse with a platelet goal of >100
- Platelet transfusions should be given to bleeding patients with consumptive platelet disorders such as DIC or TTP
Aplastic anemia is a rare disorder with a high mortality if left untreated. In essence, it is the asymptomatic autoimmune destruction of hematopoietic stem cells in the bone marrow, leading to severe pancytopenia and its associated complications. Medications, radiation, toxic chemicals, viral infections, autoimmune disorders, pregnancy, anorexia nervosa, and paroxysmal nocturnal hemoglobinuria can all trigger this autoimmune process, in theory by altering our stem cells in such a way that our immune system attacks them. Here is the illness script for aplastic anemia:
An important note about antithymocyte globulin is that it is a polyclonal antibody to human T cells manufactured from horse serum (or alternatively, rabbit serum). It must be given with prednisone and premedication with acetaminophen and diphenhydramine to reduce the risk of serum sickness. Skin testing for hypersensitivity to horse serum prior to administration is recommended.
When caring for our aplastic anemia patients, early evaluation for stem cell transplant is important. If they are eligible for transplant and a donor search is initiated, it is important to avoid any unnecessary transfusions to decrease sensitization for host antigens and reduce risk of future transplant rejection.