A 54-year-old woman is evaluated in the emergency department for a fever that started 6 ho… — USMLE Step 2 CK

A $54$ -year-old woman is evaluated in the emergency department for a fever that started $6$ hours ago. She is currently hospitalized and undergoing induction chemotherapy for acute myeloid leukemia (AML). She reports mild generalized fatigue but denies cough, shortness of breath, dysuria, abdominal pain, or diarrhea. Her temperature is $38.6^\circ\text{C}$ ( $101.5^\circ\text{F}$ ), blood pressure is $112/72 \text{ mm Hg}$ , pulse is $108/\text{min}$ , and respiratory rate is $16/\text{min}$ . Physical examination reveals a clean and intact right internal jugular central venous catheter site with no surrounding erythema, induration, or tenderness. The lungs are clear to auscultation bilaterally. There are no oral ulcers or skin rashes.

Laboratory studies show:

Parameter	Result
Hemoglobin	$8.4 \text{ g/dL}$
Platelets	$42,000/\text{mm}^3$
Leukocytes	$800/\text{mm}^3$
Neutrophils	$10\%$
Lymphocytes	$85\%$
Eosinophils	$2\%$
Monocytes	$3\%$
Serum creatinine	$0.9 \text{ mg/dL}$

Blood and urine cultures have been obtained. Which of the following is the most appropriate next step in management?

A
Intravenous vancomycin
B
Delay antibiotic therapy until culture results are available
Intravenous cefepimeCevap
D
Oral ciprofloxacin and amoxicillin-clavulanate
E
Intravenous fluconazole

Cevap

Intravenous cefepime

The correct answer is intravenous cefepime. This patient presents with a fever (

38.6^\circ\text{C}

) and an absolute neutrophil count (ANC) of

80/\text{mm}^3

, meeting the diagnostic criteria for neutropenic fever. Patients with an ANC

< 500/\text{mm}^3

have an impaired inflammatory response, meaning a fever may be the only sign of a life-threatening infection. Because the risk of rapid progression to septic shock (particularly from Pseudomonas aeruginosa and other Gram-negative bacilli) is extremely high, empiric broad-spectrum antibiotic therapy must be initiated immediately after blood and urine cultures are obtained. High-risk patients—such as those with hematologic malignancies, anticipated prolonged neutropenia (

> 7

days), or profound neutropenia (ANC

\leq 100/\text{mm}^3

)—require hospitalization and intravenous therapy with an anti-pseudomonal beta-lactam, such as cefepime, meropenem, or piperacillin-tazobactam.

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Calculate the Absolute Neutrophil Count (ANC).

\text{ANC} = \text{Total Leukocytes} \times (\% \text{Neutrophils} + \% \text{Bands})

. For this patient,

\text{ANC} = 800 \times 0.10 = 80/\text{mm}^3

ANC determines the severity of immunosuppression and risk for life-threatening bacterial infections.

Identify the clinical syndrome based on vital signs and lab results.

The patient has a fever (

38.6^\circ\text{C}

) accompanied by an ANC

< 500/\text{mm}^3

, confirming the diagnosis of neutropenic fever.

Neutropenic fever is an oncologic emergency requiring immediate recognition to prevent rapid clinical deterioration.

Risk-stratify the patient to determine the appropriate route and spectrum of antimicrobial therapy.

The patient is undergoing induction chemotherapy for acute myeloid leukemia (AML), placing her at high risk for prolonged, profound neutropenia and severe infections.

High-risk patients require inpatient intravenous therapy, whereas low-risk patients (e.g., solid tumors, stable vitals) may be managed with oral antibiotics.

Select the optimal empiric antimicrobial regimen.

Immediate administration of an empiric intravenous anti-pseudomonal beta-lactam, such as cefepime, meropenem, or piperacillin-tazobactam, is indicated.

Gram-negative bacteremia (particularly Pseudomonas aeruginosa) can cause rapid, fatal septic shock in neutropenic patients without prompt broad-spectrum coverage.

Anahtar Kavram

Neutropenic fever (temperature

\geq 38.3^\circ\text{C}

and ANC

< 500/\text{mm}^3

) in high-risk patients requires immediate empiric therapy with an intravenous anti-pseudomonal beta-lactam (e.g., cefepime, meropenem, or piperacillin-tazobactam) to prevent rapid progression to septic shock.

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