A 68-year-old woman is evaluated in the emergency department for a 2-day history of fever,… — USMLE Step 3

A $68$ -year-old woman is evaluated in the emergency department for a $2$ -day history of fever, chills, right-sided flank pain, and nausea. Her medical history is significant for a mechanical mitral valve replacement $4$ years ago, paroxysmal atrial fibrillation, and recurrent urinary tract infections. Her medications include warfarin and metoprolol. Two months ago, she was hospitalized for pyelonephritis, and blood and urine cultures at that time grew Klebsiella pneumoniae confirmed to be an extended-spectrum beta-lactamase (ESBL) producer.

Upon arrival, her temperature is $39.2^{\circ}\text{C}$ ( $102.6^{\circ}\text{F}$ ), blood pressure is $88/54\text{ mmHg}$ , pulse is $118/\text{min}$ and irregularly irregular, and respiratory rate is $22/\text{min}$ . Physical examination reveals marked right costovertebral angle tenderness.

Laboratory results:
Leukocyte count: $18,500/\text{mm}^3$
Serum creatinine: $2.4\text{ mg/dL}$ (baseline $0.8\text{ mg/dL}$ )
INR: $3.2$
Urinalysis: $3+$ leukocyte esterase, positive nitrites, $>50\text{ WBCs/hpf}$

The patient receives a $30\text{ mL/kg}$ intravenous bolus of lactated Ringer solution. Repeat blood pressure is $112/68\text{ mmHg}$ . Blood and urine cultures are obtained. Which of the following is the most appropriate next pharmacologic intervention?

Intravenous meropenemCevap
B
Intravenous ceftriaxone
C
Intravenous ciprofloxacin
D
Oral nitrofurantoin
E
Oral vitamin K

Cevap

Intravenous meropenem

The correct pharmacologic intervention is intravenous meropenem. This patient presents with sepsis secondary to acute pyelonephritis and acute kidney injury. Her recent history of infection with an extended-spectrum beta-lactamase (ESBL)-producing organism places her at high risk for a recurrent ESBL infection. Carbapenems, such as meropenem, ertapenem, and imipenem, are the standard-of-care empiric therapy for severe, life-threatening infections caused by ESBL-producing Enterobacteriaceae. Since she has already responded appropriately to initial fluid resuscitation, the immediate administration of a guideline-concordant intravenous antibiotic is the critical next step.

Adım Adım Çözüm

Diagnose the acute clinical presentation.

The patient has urosepsis secondary to acute pyelonephritis, complicated by acute kidney injury (AKI).

Fever, CVA tenderness, hypotension, leukocytosis, and pyuria confirm the diagnosis and the need for immediate, broad-spectrum intravenous antibiotics following fluid resuscitation.

Analyze microbiological risk factors.

The patient has a known history of infection with ESBL-producing Klebsiella pneumoniae.

Prior colonization or infection with ESBL organisms is the strongest predictor for recurrent ESBL infection, mandating empiric coverage with a carbapenem (e.g., meropenem, ertapenem).

Evaluate comorbid conditions and current medications against therapeutic options.

The patient has a mechanical mitral valve with a therapeutic INR (

3.2

), and acute kidney injury.

This rules out interventions that would cause dangerous drug-drug interactions (e.g., fluoroquinolones potentiating warfarin), interventions contraindicated by renal failure (e.g., nitrofurantoin), and unnecessary reversal of anticoagulation.

Anahtar Kavram

Empiric antibiotic selection for urosepsis must account for past resistant isolates (e.g., utilizing carbapenems for known ESBL history) while strictly avoiding agents contraindicated by the patient's comorbidities (AKI) or current pharmacotherapy (warfarin).

Tahmini Süre:1m 30s

Soru

Cevap

Adım Adım Çözüm

Anahtar Kavram

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