Chapters 30 and 31 provide more detailed discussions of infections in the immunocompromised patient.
ESSENTIALS OF DIAGNOSIS
In patients with neutropenia, infection is a medical emergency.
Although sometimes attributable to other causes, the presence of fever, defined as a single temperature greater than 38.3°C (101°F) or a temperature of greater than 38°C (100.4°F) for longer than 1 hour, must be assumed to be due to an infection.
Many patients with disseminated neoplasms have increased susceptibility to infection. In some patients, this results from impaired defense mechanisms (eg, acute leukemia, Hodgkin lymphoma, plasma cell myeloma, chronic lymphocytic leukemia); in others, it results from the myelosuppressive and immunosuppressive effects of cancer chemotherapy or a combination of these factors. Complicating impaired defense mechanisms are the frequent presence of indwelling catheters, impaired mucosal surfaces, and colonization with more virulent hospital-acquired pathogens.
The source of a neutropenic febrile episode is determined in about 30% of cases through blood, urine, or sputum cultures. The bacterial organisms accounting for the majority of infections in cancer patients include gram-positive bacteria (coagulase-negative Staphylococcus, Staphylococcus aureus, Streptococcus pneumoniae, Corynebacterium, and streptococci) and gram-negative bacteria (Escherichia coli, Klebsiella, Pseudomonas, Enterobacter). Gram-positive organism infections are more common, but gram-negative infections are more serious and life-threatening. The risk of bacterial infections rises when the neutrophil count is below 500/mcL (0.5 × 109/L); the risk markedly increases when the count falls below 100/mcL (0.1 × 109/L) or when there is a prolonged duration of neutropenia, typically greater than 7 days.
A thorough physical examination should be performed. However, routine DREs should be avoided unless symptoms suggest a rectal abscess or prostatitis. If a DRE is necessary, antibiotics should be administered first. Appropriate cultures (eg, blood, sputum, urine and, if indicated, cerebrospinal fluid) should always be obtained. Two sets of blood cultures should be drawn before starting antibiotics; if the patient has an indwelling catheter, one of the cultures should be drawn from the line. A chest radiograph should also be obtained.
Empiric antibiotic therapy needs to be initiated within 1 hour of presentation and following the collection of blood cultures in the febrile neutropenic patient. The choice of antibiotics depends on a number of different factors including the patient’s clinical status and any localizing source of infection. If the patient is clinically well, monotherapy with an intravenous beta-lactam with anti-Pseudomonas activity (cefepime, ceftazidime, imipenem/cilastatin, piperacillin/tazobactam) should be started (see Infections in the Immunocompromised Patient, Chapter 30). If the patient is clinically ill with hypotension or hypoxia, an intravenous aminoglycoside or fluoroquinolone should be added for “double” gram-negative bacteria coverage. If there is a strong suspicion of a gram-positive organism, such as from S aureus catheter infection, intravenous vancomycin can be given empirically. Low-risk ...