A 3-year-old boy is brought to the pediatrician's office during the winter with a 4-day hi… — USMLE Step 2 CK

A $3$ -year-old boy is brought to the pediatrician's office during the winter with a $4$ -day history of high fever, worsening cough, and rapid breathing. The mother reports that he has been less active than usual but continues to drink fluids well. He has no significant past medical history and is up to date on all immunizations. His temperature is $39.2^{\circ}\text{C}$ ( $102.6^{\circ}\text{F}$ ), pulse is $135\text{/min}$ , respirations are $42\text{/min}$ , and blood pressure is $94/60\text{ mm Hg}$ . Oxygen saturation is $96\%$ on room air. He is alert and interactive. Physical examination reveals focal crackles and decreased breath sounds over the left lower lung field. There are no retractions, diffuse wheezing, or stridor. Which of the following is the most appropriate next step in management?

Oral high-dose amoxicillinAnswer
B
Oral azithromycin
C
Oral amoxicillin-clavulanate
D
Intravenous ceftriaxone
E
Inhaled albuterol therapy

Answer

Oral high-dose amoxicillin

The correct answer is oral high-dose amoxicillin. This patient presents with classic signs of community-acquired pneumonia (CAP), including fever, tachypnea, and focal lung findings (crackles and decreased breath sounds). In a fully immunized preschool-aged child (under 5 years of age), typical bacterial pneumonia is overwhelmingly caused by Streptococcus pneumoniae. The patient is hemodynamically stable, well-hydrated, and not hypoxic, meaning outpatient management is safe and appropriate. According to current guidelines, oral high-dose amoxicillin is the first-line empiric therapy for uncomplicated outpatient CAP in this age group.

Step-by-Step Solution

Analyze the clinical presentation.

The patient has a high fever, tachypnea, and focal crackles in the left lower lung field without diffuse wheezing.

These classic findings point to a focal bacterial infection, specifically community-acquired pneumonia (CAP), rather than a viral upper respiratory infection or reactive airway disease.

Determine the most likely pathogen.

Streptococcus pneumoniae is the most common bacterial etiology.

In a fully immunized preschool-aged child (under 5 years old), typical bacterial pneumonia is most frequently caused by S. pneumoniae, whereas atypical pathogens become more common in older children.

Assess disease severity to choose the treatment setting.

The patient is stable for outpatient management.

Despite the fever and tachypnea, the patient has normal oxygen saturation (96%), normal blood pressure, and is tolerating oral fluids well without severe respiratory distress.

Select the appropriate pharmacotherapy.

Oral high-dose amoxicillin.

High-dose amoxicillin (90 mg/kg/day) is the recommended first-line empiric therapy for outpatient management of suspected pneumococcal CAP in children.

Key Concept

First-line empiric antibiotic therapy for typical community-acquired pneumonia in preschool-aged children.

Estimated Time:1m 15s

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