A 48-year-old man comes to the emergency department due to a 5-day history of fever, right… — USMLE Step 2 CK

A $48$ -year-old man comes to the emergency department due to a $5$ -day history of fever, right-sided chest pain that worsens with deep breathing, and a productive cough with foul-smelling sputum. He has a history of alcohol use disorder. Temperature is $39.2^\circ\text{C}$ ( $102.6^\circ\text{F}$ ), blood pressure is $110/70$ mm Hg, pulse is $112$ /min, and respiratory rate is $24$ /min. Pulse oximetry is $94\%$ on room air.

Physical examination reveals poor dentition. Lung auscultation demonstrates decreased breath sounds, dullness to percussion, and decreased tactile fremitus over the lower right lung field.

Chest radiograph shows a large right-sided pleural effusion with loculations.

Diagnostic thoracentesis yields turbid pleural fluid with the following analysis:

Parameter	Pleural Fluid	Serum
Protein	$4.8$ g/dL	$6.2$ g/dL
Lactate dehydrogenase (LDH)	$1050$ U/L	$180$ U/L
Glucose	$28$ mg/dL	$110$ mg/dL
pH	$7.12$	$7.40$
Leukocytes	$25,000/\text{mm}^3$ ( $85\%$ neutrophils)	$8,500/\text{mm}^3$

Gram stain of the fluid shows many polymorphonuclear leukocytes but no organisms are seen. The patient is promptly started on intravenous ampicillin-sulbactam.

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

Placement of a thoracostomy tubeAnswer
B
Administration of intravenous furosemide
C
Broadening of antimicrobial therapy to intravenous vancomycin and cefepime
D
Administration of intravenous sodium bicarbonate
E
Continuation of current therapy with clinical observation

Answer

Placement of a thoracostomy tube

This patient's presentation of fever, foul-smelling sputum, and poor dentition strongly suggests aspiration pneumonia caused by anaerobic oral flora, which has subsequently led to a large, loculated pleural effusion. Application of Light's criteria confirms an exudative effusion (pleural-to-serum protein ratio

> 0.5

and LDH ratio

> 0.6

). Furthermore, the pleural fluid analysis demonstrates a pH of

7.12

and a glucose level of

28

mg/dL. In the setting of pneumonia, a parapneumonic effusion is considered 'complicated' if it exhibits a pH

< 7.20

, a glucose level

< 60

mg/dL, or if bacteria are visualized on Gram stain. Complicated parapneumonic effusions and empyemas (frank pus in the pleural space) require urgent mechanical drainage via a thoracostomy tube. Intravenous antibiotics alone cannot effectively penetrate the acidic, loculated environment to achieve adequate source control.

Step-by-Step Solution

Identify the primary clinical syndrome.

Aspiration pneumonia leading to a loculated pleural effusion.

The patient has a history of alcohol use disorder, poor dentition, foul-smelling sputum, and a right lower lung consolidation with effusion.

Analyze the pleural fluid using Light's criteria.

The fluid is an exudate.

The pleural-to-serum protein ratio is

4.8/6.2 = 0.77

(

> 0.5

) and the LDH ratio is

1050/180 = 5.8

(

> 0.6

Determine if the effusion is complicated.

The effusion is a complicated parapneumonic effusion or early empyema.

The pleural fluid analysis reveals a pH of

7.12

(

< 7.20

) and a glucose level of

28

mg/dL (

< 60

mg/dL).

Select the appropriate definitive management.

Placement of a thoracostomy tube (chest tube).

Antibiotics alone cannot effectively penetrate the loculated, acidic environment of a complicated effusion; mechanical source control is required.

Key Concept

Complicated parapneumonic effusions and empyemas are characterized by a pleural fluid pH

< 7.20

, glucose

< 60

mg/dL, or a positive Gram stain/culture. They require urgent mechanical drainage via a thoracostomy tube in addition to appropriate intravenous antibiotics.

Estimated Time:1m 30s

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