A 56-year-old man is admitted to the hospital with a 2-day history of diffuse abdominal pa… — USMLE Step 2 CK

A 56-year-old man is admitted to the hospital with a 2-day history of diffuse abdominal pain, nausea, and progressive lethargy. He has a history of alcohol-associated cirrhosis and portal hypertension. On presentation, his temperature is $38.2^\circ\text{C}$ ( $100.8^\circ\text{F}$ ), blood pressure is $105/65\text{ mmHg}$ , heart rate is $98/\text{min}$ , and respiratory rate is $20/\text{min}$ . Physical examination shows scleral icterus, spider angiomata, and moderate abdominal distension with shifting dullness. There is diffuse abdominal tenderness but no rebound or guarding. Bowel sounds are hypoactive. Asterixis is present. Arterial blood gas analysis on room air reveals the following:

Parameter	Value
pH	$7.31$
$\text{pCO}_2$	$31\text{ mmHg}$
$\text{pO}_2$	$85\text{ mmHg}$
$\text{HCO}_3^-$	$15\text{ mEq/L}$

Diagnostic paracentesis is performed, and ascitic fluid analysis shows:

Parameter	Value
Total protein	$1.1\text{ g/dL}$
Total leukocyte count	$400/\text{mm}^3$
Neutrophils	$70\%$
Glucose	$65\text{ mg/dL}$

Gram stain of the fluid shows no organisms.

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

Intravenous cefotaximeCevap
B
Intravenous piperacillin-tazobactam and vancomycin
C
Nasogastric tube insertion and bowel rest
D
Intravenous sodium bicarbonate
E
Increase doses of oral furosemide and spironolactone

Cevap

Intravenous cefotaxime is the most appropriate next step because the absolute neutrophil count in the ascitic fluid confirms the diagnosis of spontaneous bacterial peritonitis.

The correct answer is intravenous cefotaxime. This patient with cirrhosis presents with fever, abdominal pain, altered mental status, and a fully compensated metabolic acidosis. His ascitic fluid analysis reveals an absolute neutrophil count (ANC) of

400 \times 0.70 = 280/\text{mm}^3

. An ascitic fluid ANC

\geq 250/\text{mm}^3

is diagnostic for spontaneous bacterial peritonitis (SBP). Because SBP is associated with high mortality, empiric antibiotic therapy must be initiated immediately after fluid collection, without waiting for culture results. The treatment of choice is a third-generation cephalosporin, such as intravenous cefotaxime or ceftriaxone, which effectively covers the most common causative organisms (e.g., Escherichia coli, Klebsiella pneumoniae, and Streptococcus pneumoniae).

Adım Adım Çözüm

Calculate the absolute neutrophil count (ANC) in the ascitic fluid.

The ANC is

400 \times 0.70 = 280/\text{mm}^3

An ANC

\geq 250/\text{mm}^3

is the diagnostic threshold for spontaneous bacterial peritonitis (SBP).

Evaluate the arterial blood gas using Winter's formula to interpret the acid-base status.

Expected

\text{pCO}_2 = 1.5 \times 15 + 8 = 30.5 \pm 2\text{ mmHg}

. Measured is

31\text{ mmHg}

, confirming full respiratory compensation.

To rule out a superimposed respiratory acid-base disorder and determine if targeted acid-base therapy (e.g., bicarbonate) is needed.

Select the appropriate targeted empiric pharmacotherapy for SBP.

Intravenous cefotaxime (or ceftriaxone) should be initiated.

Third-generation cephalosporins provide optimal empiric coverage for the enteric organisms that typically cause SBP, balancing high efficacy with appropriate antibiotic stewardship.

Anahtar Kavram

Diagnosis and empiric management of Spontaneous Bacterial Peritonitis (SBP)

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Cevap

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