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Zorluk: ZorPreoperative and Postoperative Care

A 72-year-old man is evaluated for decreased urine production on the evening of his first postoperative day. Earlier that morning, he underwent an elective open repair of an infrarenal abdominal aortic aneurysm. His medical history is notable for coronary artery disease, ischemic cardiomyopathy with a left ventricular ejection fraction of 35%, and diet-controlled type 2 diabetes mellitus. Over the past 3 hours, urine output via his indwelling urethral catheter has been 12 mL/hr. The catheter was just flushed with sterile saline and is patent. Vital signs include a temperature of 38.1°C (100.6°F), blood pressure of 94/58 mm Hg, heart rate of 114/min, and respiratory rate of 18/min. Pulse oximetry shows 96% on room air. The patient appears lethargic but is easily arousable. Jugular venous pressure is estimated at 3 cm H2O. Lungs are clear to auscultation bilaterally. Cardiac examination reveals a regular, rapid rhythm with no murmurs or S3 gallop. The abdominal dressing is dry and intact; the abdomen is diffusely tender to palpation but lacks rigidity or rebound.

Laboratory studies:
Hemoglobin: 11.2 g/dL
Leukocyte count: 11,500/mm³
Serum sodium: 136 mEq/L
Serum potassium: 4.6 mEq/L
Blood urea nitrogen: 42 mg/dL
Serum creatinine: 1.9 mg/dL (Baseline: 1.1 mg/dL)
Urine sodium: 8 mEq/L
Fractional excretion of sodium (FENa): 0.6%

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

  1. Administration of a balanced crystalloid fluid bolusCevap
  2. B
    Intravenous furosemide administration
  3. C
    Continuous dobutamine infusion
  4. D
    Blood cultures and empirical broad-spectrum antibiotics
  5. E
    Abdominal and pelvic ultrasonography

Cevap

The most appropriate next step is the administration of a balanced crystalloid fluid bolus to treat pre-renal acute kidney injury caused by hypovolemia.
The correct action is to administer a balanced crystalloid fluid bolus. This patient is presenting with oliguria and an acute rise in serum creatinine on postoperative day 1 following a major vascular procedure. The primary diagnostic challenge is distinguishing between pre-renal acute kidney injury (AKI) due to hypovolemia and intrinsic/post-renal causes, particularly given his history of heart failure (EF 35%). The laboratory findings heavily strongly favor a pre-renal etiology: a BUN/creatinine ratio of 22 (normal is ~10-15), a urine sodium of 8 mEq/L (normal is > 40 in intrinsic renal disease), and a Fractional Excretion of Sodium (FENa) of 0.6% (values < 1% indicate the kidneys are appropriately retaining sodium in response to poor perfusion). Furthermore, the physical examination confirms hypovolemia rather than volume overload or isolated pump failure. His jugular venous pressure is low, and his lungs are entirely clear to auscultation without an S3 gallop. In the setting of third-spacing and insensible fluid losses associated with major open abdominal surgery, the patient is severely volume-depleted. He requires prompt, though carefully monitored, intravenous fluid resuscitation to restore renal perfusion and prevent progression to acute tubular necrosis.

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1
Evaluate the cause of postoperative oliguria and acute kidney injury.
The patient's BUN to creatinine ratio is greater than 20:1, urine sodium is < 20 mEq/L, and FENa is < 1%.
These specific laboratory values strongly indicate a pre-renal etiology for the acute kidney injury, typically caused by renal hypoperfusion.
2
Assess the patient's volume status and hemodynamics.
The patient is hypotensive, tachycardic, has a low jugular venous pressure (3 cm H2O), and his lungs are clear to auscultation.
Despite the history of ischemic cardiomyopathy and a low ejection fraction (35%), the physical exam definitively shows intravascular volume depletion rather than fluid overload or cardiogenic shock.
3
Determine the most appropriate immediate intervention.
Volume resuscitation with isotonic intravenous fluids is required.
Restoring intravascular volume will improve renal perfusion and reverse the pre-renal acute kidney injury. The patient's heart failure history necessitates careful monitoring during resuscitation, but it does not contraindicate the needed fluids.

Anahtar Kavram

In patients with a history of heart failure, postoperative oliguria and hypotension must be carefully evaluated with physical exam and urine studies to differentiate hypovolemia (requiring fluid resuscitation) from cardiogenic shock or fluid overload (requiring diuresis or inotropes).
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Preoperative and Postoperative Care

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