Infections in the Neutropenic Patient

Patients receiving cancer chemotherapy are at high risk for developing neutropenia and severe infections when their neutrophil count is depressed. There is no strict definition of neutropenia, but this term is used to define an absolute neutrophil count ≤1500 cells down to an absolute neutrophil count ≤500 cells/mL. Fever in the neutropenic patient is defined as a single temperature of >38.3°C or a temperature of >38.0°C over at least 30 minutes to 1 hour. However, some neutropenic patients do not mount a fever, and the presence of hypotension and hypothermia may be the presenting feature of infection. Over the years, different approaches have been developed to address the clinical entity of fever and neutropenia. Some research has looked at preventing neutropenia with the use of colony-stimulating factors. Other research has focused on preventing infection in the neutropenic patient; still others have looked at the empiric use of antimicrobials to treat infections when fever occurs. In this chapter, I focus on these three approaches as well as the main causes of infections in these severely immunocompromised individuals. CAUSES OF INFECTION IN THE NEUTROPENIC PATIENT Gram-Negative Organisms Enteric gram-negative organisms play a significant role in the morbidity and mortality due to infection in our neutropenic patients. These include Escherichia coli, Klebsiella spp., and Enterobacter spp. among others. These organisms can gain entry into the bloodstream and lead to serious infections as a result of mucosal damage and the ability of the organism to disseminate.