Febrile neutropenia

Febrile neutropenia is a common condition that requires an organized approach and awareness of how this situation differs from fever in the immunocompetent patient.

Neutropenia:
Textbook definition of neutropenia as absolute neutrophil count (ANC) below 1000. A more practical definition is below 500, because this is when risk of serious infection increases significantly. At below 100, there is a high risk of invasive infections and spontaneous bacteremias.

Fever:
Single oral temperature of 38.3 or higher, or multiple readings of 38.0 or higher.

Clinical consequences of febrile neutropenia are dictated by
1) severity of neutropenia
2) duration

A source of infection is found in only 30-40% of cases. When a source is found, the most common sites are
1) Skin (mucosal or perianal)
2) Bacteremia (line-related or spontaneous)
3) Pulmonary

This leads to the following usual culprit organisms:
Bacteria:
GP- (staph aureus, coag-neg staph, strep viridans, enterococcus). NB- GPs more likely if pt was on FN prophyaxis (usu. fluoroquinolone). These usually originate from skin/lines
GN- aerobes (e. coli, enterobacter, pseudomonas, klebsiella). These usually originate from GI/hospital env't
NB- FN pts are not at higher risk for anaerobes, encapsulated, or intracellular organsms.

Fungi:
Candida- albicans, others; aspergillus- usu with prolonged neutropenia; mucor

Viral:
Not at particular risk because intracellular; HSV may reactivate, but this is more from "stress" than neutropenia.

Tx: 1) cover common organisms 2) modify regimen for suspected source or specific deficits (eg. add vanco if suspected line infection; add anaerobic coverage if suspect c. diff, typhlitis, sinusitis or periodontal, perirectal; add azith/levo if pneumonia, acyclovir, nystatin or fluco for mucositis)

Possible initial regimens: Pip-tazo alone; cefazolin + tobra; carbapenems, others...

Some guidelines on duration of therapy
If patient is afebrile in 3-5d, treat for usual duration for source identified.
If ANC is over 500 for 48h, consider stopping Abx if source not found
If patient remains febrile and neutropenic for over 3-5d, consider broadening antibiotics (if applicable) and / or adding antifungal empirically

Low risk FN
If all of these conditions are met, may treat orally at home with close followup:
1) hemodynamically stable
2) normal CXR
3) no medical comorbidities
4) normal mental status
5) expected duration of neutropenia less than 10d.
6) access to medical care 24/7
7) not weekend
8) no focus of infection identified

Oral regimen: Amoxicillin-clavulin and ciprofloxacin PO

Links:
Click here for IDSA febrile neutropenia guidelines
Click here for evidence behind low risk outpatient treatment described above