Platelets and RBCs are more radioresistant because they are terminally differentiated, have no nuclei, and are therefore not mitotically active. It is their precursor cells in the marrow that are sensitive to IR, but because of their life cycle, thrombocytopenia and anemia may not manifest for weeks. Therefore, infusions of platelets or packed RBCs are not required in the first 72 hours unless they are needed to maintain hemostasis and oxygen delivery owing to blood loss and ongoing hemorrhage from concomitant trauma. However, if the patient's estimated dose is greater than 2 Gy, HLA antigen typing should be performed as soon as possible (e-mail communication, W. Navarro, MD, May 2011). Further, if the patient's dose is greater than 2 Gy, colony-stimulating factors (CSFs), filgrastim (a granulocyte CSF), or sargramostim (a granulocyte-macrophage CSF) should be started as soon as possible,
12 as should prophylactic antimicrobial drugs. As the patient becomes more neutropenic (<500 cells/mm
3), and especially with profound neutropenia (<100 cells/mm
3), a careful search for any infection should be conducted and specific foci of infection treated adequately. Serologic testing should be done immediately for herpes simplex virus and cytomegalovirus. If the patient has a positive history of either of these infectious diseases, prophylaxis should be initiated with acyclovir or ganciclovir, respectively. Other antimicrobial drugs should be considered for
Candida and resistant species of
Candida, as well as
Aspergillus and
Pneumocystis jirovecii. Recommendations may be found in the Infectious Disease Society of America guidelines for febrile neutropenic patients.
13 Consultation with an infectious disease specialist should always be considered.
13 The World Health Organization (WHO) Consultancy gives a weak evidence-based recommendation for prophylaxis with a fluoroquinolone.
12,13 Streptococcus viridans bacteremia is another potential infectious disease in these patients. Clinically, patients may exhibit infection, petechiae, epistaxis, bleeding from gums, and hemorrhage. The bone marrow will show aplastic anemia, almost void of cells. Consultation with hematopathology or a bone marrow transplant center such as the Radiation Injury Treatment Network should be considered. Dainiak et al
12 provide an excellent review of recommendations for the use of cytokines and stem cell transplants for the nonhematopathologist.
12