Empiric Antimicrobial Therapy in the Febrile Granulocytopenic Patient

Abstract

In the normal individual, about 100 billion polymorphonuclear leukocytes (neutrophils) enter the bloodstream daily from the bone marrow. About half of the intravascular neutrophils are adherent (marginated) to the endothelium of small vessels and the remainder are circulating. Without unusual disturbances, the half-life of the intravascular neutrophil is about six hours. Although the number of circulating neutrophils seems enormous, it represents only 5% of the total body content of these cells, the major portion residing in the bone marrow.It is remarkable that quantitation of polymorphonuclear leukocytes in a drop of peripheral blood can be highly predictive of an individual's resistance and response to infectious diseases, especially those caused by bacteria. Neutrophil activity is complex and its role in host defense is dependent upon factors other than quantity. Nevertheless, when the absolute neutrophil count is maintained at values less than 1000/cu mm, increased susceptibility to infection occurs and is at a rate that is inversely proportional to the neutrophil count. When the count is decreased to values of 500 neutrophils/cu mm or less, the frequency of serious bacterial infection reaches a point where special attention must be directed to the patient at the earliest sign of infection.