A 6-year-old boy is brought to the emergency department by his parents due to a new-onset … — USMLE Step 2 CK

A $6$ -year-old boy is brought to the emergency department by his parents due to a new-onset fever and a mild cough that started earlier today. The patient was diagnosed with acute lymphoblastic leukemia (ALL) $4$ months ago and is currently receiving maintenance chemotherapy. His last chemotherapy cycle was $10$ days ago. His temperature is $39.4^\circ\text{C}$ ( $102.9^\circ\text{F}$ ), pulse is $125/\text{min}$ , respirations are $24/\text{min}$ , and blood pressure is $95/60 \text{ mmHg}$ . On physical examination, the child appears pale and mildly lethargic but is easily rousable. Lung auscultation is clear bilaterally without wheezing or crackles. There is a central venous port in the right upper chest with no surrounding erythema or induration.

Laboratory studies show:
Leukocyte count: $800/\mu\text{L}$
- Neutrophils: $15\%$
- Lymphocytes: $80\%$
- Monocytes: $5\%$
Hemoglobin: $9.2 \text{ g/dL}$
Platelet count: $85,000/\mu\text{L}$

Which of the following is the most appropriate next step in the management of this patient?

Obtain blood cultures and immediately initiate empiric broad-spectrum intravenous antibioticsCevap
B
Withhold systemic antimicrobial therapy until blood and sputum culture sensitivities are finalized
C
Administer inhaled bronchodilators and oral corticosteroids for an acute reactive airway exacerbation
D
Initiate immediate intravenous furosemide for suspected chemotherapy-induced acute decompensated heart failure
E
Administer the live-attenuated intranasal influenza vaccine to prevent worsening respiratory viral illness

Cevap

Obtain blood cultures and immediately initiate empiric broad-spectrum intravenous antibiotics.

The correct step is to immediately obtain blood cultures and start empiric broad-spectrum intravenous antibiotics. This patient has febrile neutropenia, defined as a single oral temperature

\ge 38.3^\circ\text{C}

(

101.0^\circ\text{F}

) or a sustained temperature

\ge 38.0^\circ\text{C}

(

100.4^\circ\text{F}

) for over

1

hour, accompanied by an absolute neutrophil count (ANC)

< 500/\mu\text{L}

. This patient's ANC is calculated as total WBC multiplied by the percentage of neutrophils (

800/\mu\text{L} \times 0.15 = 120/\mu\text{L}

). Because neutropenic patients lack an adequate cellular immune response, typical signs of localized infection (like abscess formation or pulmonary infiltrates) are often absent, and bacterial infections (especially Gram-negative pathogens like *Pseudomonas aeruginosa*) can rapidly progress to fatal septic shock. Therefore, prompt blood cultures followed by immediate anti-pseudomonal beta-lactam therapy (e.g., cefepime, piperacillin-tazobactam, or meropenem) is mandatory.

Adım Adım Çözüm

Calculate the Absolute Neutrophil Count (ANC).

ANC = Total WBC

\times

(% Neutrophils + % Bands) =

800 \times 0.15 = 120/\mu\text{L}

Determining the ANC is required to identify if the patient has severe neutropenia (defined as ANC

< 500/\mu\text{L}

Combine the ANC calculation with the patient's vital signs.

The patient has a fever of

39.4^\circ\text{C}

(

102.9^\circ\text{F}

) and an ANC of

120/\mu\text{L}

Fever in the presence of severe neutropenia meets the criteria for febrile neutropenia, which is a life-threatening oncologic emergency.

Determine the initial management for febrile neutropenia.

Immediate acquisition of blood cultures followed by the administration of empiric broad-spectrum intravenous antibiotics (e.g., cefepime, meropenem, or piperacillin-tazobactam).

Patients with severe neutropenia lack the inflammatory cells to localize infection, making them highly susceptible to rapid progression to septic shock, particularly from Gram-negative organisms like Pseudomonas aeruginosa.

Anahtar Kavram

Febrile Neutropenia Management

Soru

Cevap

Adım Adım Çözüm

Anahtar Kavram

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