A 54-year-old man presents to the emergency department with a 5-day history of high fever,… — USMLE Step 2 CK

A $54$ -year-old man presents to the emergency department with a $5$ -day history of high fever, productive cough with rust-colored sputum, and sharp right-sided chest pain that worsens with deep inspiration. He has no significant past medical history other than a $20$ -pack-year smoking history.

His temperature is $38.9^\circ\text{C}$ ( $102.0^\circ\text{F}$ ), blood pressure is $122/78\text{ mm Hg}$ , pulse is $110/\text{min}$ , and respiratory rate is $24/\text{min}$ . Pulse oximetry shows $92\%$ on room air.

Physical examination reveals dullness to percussion and decreased breath sounds over the right lower lung field. A chest radiograph demonstrates a right lower lobe consolidation with a moderate-sized, free-flowing right-sided pleural effusion.

A diagnostic thoracentesis is performed, and pleural fluid analysis yields the following results:

Test	Result
Appearance	Turbid
$\text{pH}$	$7.12$
Glucose	$28\text{ mg/dL}$
Protein	$4.5\text{ g/dL}$ (Serum: $6.0\text{ g/dL}$ )
Lactate dehydrogenase (LDH)	$1200\text{ U/L}$ (Serum: $200\text{ U/L}$ )
Gram stain	Gram-positive diplococci

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

Chest tube placement and targeted intravenous antibioticsAnswer
B
Intravenous piperacillin-tazobactam and daily chest radiographs
C
Intravenous furosemide and noninvasive positive pressure ventilation
D
Intravenous sodium bicarbonate infusion and repeat thoracentesis
E
Systemic corticosteroids and inhaled bronchodilators

Answer

The correct management is chest tube placement and targeted intravenous antibiotics.

The correct answer identifies that this patient has a complicated parapneumonic effusion. A parapneumonic effusion is considered 'complicated' (meaning it is highly unlikely to resolve with antibiotics alone) if it meets any of the following criteria:

\text{pH} < 7.20

, glucose

< 60\text{ mg/dL}

, or direct evidence of microbes (positive Gram stain or culture). This patient meets all three criteria. The standard of care for a complicated parapneumonic effusion or frank empyema is prompt chest tube placement for drainage (source control) combined with targeted intravenous antibiotics based on the Gram stain.

Step-by-Step Solution

Evaluate the pleural fluid using Light's criteria to determine if it is an exudate or transudate.

The pleural fluid-to-serum protein ratio is

4.5/6.0 = 0.75

(

> 0.5

) and the LDH ratio is

1200/200 = 6.0

(

> 0.6

). The fluid is highly exudative.

Differentiating exudate from transudate narrows the differential diagnosis; exudates typically result from local pleural inflammation or infection.

Assess the specific biochemical and microbiological characteristics of the exudative fluid.

The fluid has a

\text{pH}

7.12

, glucose of

28\text{ mg/dL}

, and a positive Gram stain showing Gram-positive diplococci.

These findings specifically define a complicated parapneumonic effusion (or empyema), which behaves like an abscess in the pleural space.

Determine the appropriate therapeutic intervention for a complicated parapneumonic effusion.

The patient requires immediate pleural space drainage (chest tube thoracostomy) along with pathogen-directed antibiotics.

Antibiotics alone cannot adequately penetrate and clear a highly inflamed, acidic, and loculated pleural space infection; mechanical drainage is mandatory for source control.

Key Concept

Patients with pneumonia who develop a pleural effusion with a

\text{pH} < 7.20

, glucose

< 60\text{ mg/dL}

, or positive Gram stain/culture have a complicated parapneumonic effusion (empyema) requiring immediate chest tube drainage and antibiotics.

Estimated Time:1m 15s

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