A 68-year-old male is evaluated in the intensive care unit on postoperative day 2 followin… — USMLE Step 2 CK

A $68$ -year-old male is evaluated in the intensive care unit on postoperative day $2$ following an emergent open repair of a ruptured abdominal aortic aneurysm. During the procedure, he received $8\text{ L}$ of crystalloid and $6$ units of packed red blood cells. The patient remains intubated and mechanically ventilated. Over the past $4$ hours, his urine output has dropped to $5\text{ mL/hr}$ . Current vital signs include a temperature of $38.1^\circ\text{C}$ ( $100.6^\circ\text{F}$ ), blood pressure of $82/50\text{ mmHg}$ , and heart rate of $124/\text{min}$ . The ventilator is alarming for high peak airway pressures, which have increased from $24\text{ cm H}_2\text{O}$ to $48\text{ cm H}_2\text{O}$ since the morning. Central venous pressure is $19\text{ mmHg}$ . Physical examination reveals a tightly distended, firm abdomen and bilateral basilar crackles. Laboratory studies demonstrate a serum creatinine of $2.7\text{ mg/dL}$ (baseline $1.0\text{ mg/dL}$ ) and a leukocyte count of $15,500/\mu\text{L}$ . Which of the following is the most appropriate next step in management?

Measurement of intravesical pressureAnswer
B
Intravenous administration of furosemide
C
Transport for computed tomography of the abdomen
D
Initiation of empiric broad-spectrum antibiotics
E
Insertion of a nasogastric tube for decompression

Answer

Measurement of intravesical pressure

The patient exhibits classic signs of abdominal compartment syndrome (ACS), a known complication of massive volume resuscitation, particularly following aortic surgery or major trauma. The elevated intra-abdominal pressure compresses intra-abdominal organs and venous structures, causing acute kidney injury (oliguria, rapidly rising creatinine). The pressure also transmits across the diaphragm into the chest cavity, leading to elevated intrathoracic pressure. This pathophysiologic shift decreases venous return to the heart (resulting in hypotension and tachycardia), increases peak airway pressures on the ventilator, and causes basilar atelectasis (crackles) while falsely elevating central venous pressure (CVP). The most appropriate next step to confirm the diagnosis is measuring intravesical (bladder) pressure, which provides an accurate reflection of intra-abdominal pressure. A pressure

>20\text{ mmHg}

with new organ dysfunction confirms ACS, necessitating decompressive laparotomy.

Step-by-Step Solution

Identify the primary clinical syndrome from the vital signs and physical exam findings.

The patient has a tense abdomen, oliguria, hypotension, elevated peak airway pressures, and falsely elevated CVP following massive volume resuscitation.

Recognizing this triad of abdominal, renal, and cardiopulmonary dysfunction is necessary to suspect abdominal compartment syndrome (ACS).

Analyze the pathophysiology connecting the symptoms.

Increased intra-abdominal pressure compresses the renal veins (causing oliguria) and pushes the diaphragm cephalad into the thoracic cavity. This increases intrathoracic pressure, driving up peak airway pressures, falsely elevating CVP, and decreasing venous return (causing hypotension).

Understanding the mechanical transmission of pressure explains why the patient appears to be in cardiogenic shock (high CVP, crackles) when they are actually experiencing obstructive shock.

Select the appropriate diagnostic intervention for the suspected condition.

The standard diagnostic test for ACS is the measurement of intra-abdominal pressure, which is most accurately and safely estimated via a bladder catheter (intravesical pressure).

A pressure

>20\text{ mmHg}

combined with new organ dysfunction confirms the diagnosis of ACS, dictating the need for a decompressive laparotomy.

Key Concept

Abdominal compartment syndrome is characterized by intra-abdominal hypertension leading to multiorgan dysfunction (renal failure, respiratory compromise, hypotension), diagnosed via intravesical pressure measurement.

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic