A 74-year-old man is evaluated in the surgical intensive care unit on postoperative day 2 … — USMLE Step 2 CK

A 74-year-old man is evaluated in the surgical intensive care unit on postoperative day 2 following an open repair of an infrarenal abdominal aortic aneurysm. During the surgery, the inferior mesenteric artery was noted to be patent but was ligated to facilitate placement of the synthetic aortic graft. The patient's past medical history is significant for hypertension, hyperlipidemia, and coronary artery disease. Two hours ago, he began complaining of severe, escalating left lower quadrant abdominal pain. Over the last 30 minutes, he has become increasingly lethargic and less responsive. Current vital signs show a temperature of $38.9^\circ\text{C}$ ( $102.0^\circ\text{F}$ ), blood pressure of $76/40 \text{ mmHg}$ , heart rate of $134/\text{min}$ , and respiratory rate of $24/\text{min}$ . Physical examination reveals a tensely distended abdomen with diffuse guarding, severe rebound tenderness, and absent bowel sounds. Laboratory studies show:

Leukocyte count: $24,000/\text{mm}^3$
Serum lactate: $9.4 \text{ mmol/L}$ (normal: $0.5-2.2 \text{ mmol/L}$ )
Arterial blood gas:
$pH$ : $7.12$
$pCO_2$ : $30 \text{ mmHg}$
$pO_2$ : $88 \text{ mmHg}$

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

Emergent exploratory laparotomyCevap
B
CT angiography of the abdomen and pelvis
C
Flexible sigmoidoscopy and broad-spectrum antibiotics
D
Obtaining blood cultures, urinalysis, and portable chest radiograph
E
Administration of intravenous furosemide and dobutamine

Cevap

Emergent exploratory laparotomy

The correct answer is emergent exploratory laparotomy. This patient is presenting with acute transmural colonic infarction resulting in peritonitis and septic shock. During an open abdominal aortic aneurysm (AAA) repair, the inferior mesenteric artery (IMA) is often ligated. If collateral blood flow from the superior mesenteric artery is insufficient, ischemic colitis occurs. While mild ischemic colitis involves only the mucosa and presents with self-limiting abdominal pain and bloody diarrhea, transmural infarction presents with peritoneal signs (guarding, severe rebound tenderness), profound lactic acidosis, and hemodynamic instability. In a patient with definitive peritonitis and shock, immediate surgical exploration to resect the necrotic bowel is life-saving. Any diagnostic delay for imaging or endoscopy is strictly contraindicated.

Adım Adım Çözüm

Identify the risk factor for ischemia based on the surgical history.

The patient underwent an open abdominal aortic aneurysm (AAA) repair with ligation of a patent inferior mesenteric artery (IMA).

Ligation of the IMA predisposes the patient to colonic ischemia if collateral circulation via the marginal artery of Drummond or the arc of Riolan is inadequate.

Analyze the acute clinical presentation and physical examination.

The patient developed severe left lower quadrant pain progressing to a rigid abdomen with rebound tenderness, fever, and leukocytosis.

These are classic peritoneal signs indicating that the colonic ischemia has progressed to transmural bowel infarction and likely perforation.

Assess the patient's hemodynamic status and laboratory values.

The patient is in profound shock (blood pressure

76/40 \text{ mmHg}

, heart rate

134/\text{min}

, profound lactic acidosis with lactate

9.4 \text{ mmol/L}

Transmural infarction leads to massive fluid shifts, bacterial translocation, and overwhelming septic shock.

Determine the definitive next step in management based on stability and abdominal exam.

Immediate exploratory laparotomy is required.

Hemodynamically unstable patients with an acute surgical abdomen (peritonitis) require emergent operative intervention for source control; diagnostic imaging or endoscopic delays are strictly contraindicated.

Anahtar Kavram

Patients with acute transmural colonic infarction presenting with peritonitis and hemodynamic instability require emergent exploratory laparotomy.

Soru

Cevap

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