What is the most appropriate next step in managing a patient with a stab wound to the central abdomen, presenting with normotension, and mild hypoxemia?

Management of Central Abdominal Stab Wound with Hemodynamic Stability

Perform FAST (Focused Assessment with Sonography for Trauma) immediately as the next step in management for this hemodynamically stable patient with penetrating abdominal trauma. 1

Rationale for FAST as Initial Diagnostic Step

This patient is hemodynamically stable (systolic BP 116 mmHg, which is ≥90 mmHg per ACR definition), making FAST the appropriate initial imaging modality rather than immediate laparotomy. 1

• FAST can be performed rapidly at bedside (8-10 minutes) to detect hemopericardium, pneumothorax, and free intraperitoneal fluid, which have significant implications for next management steps. 1, 2

• The American College of Radiology specifically recommends FAST to help triage penetrating trauma patients and direct initial bedside and surgical procedures. 1

• FAST has high sensitivity (0.92) and specificity (0.95-1.0) for detecting hemoperitoneum in trauma patients, including those with penetrating injuries. 1, 3

Clinical Algorithm Based on FAST Results

If FAST is Positive (Free Fluid Present):

• Proceed immediately to CT abdomen/pelvis with IV contrast if the patient remains hemodynamically stable to characterize the injury, identify bleeding source, and determine operative versus non-operative management. 4

• Contrast-enhanced CT is critical for accurately characterizing solid organ injuries (liver, spleen, kidney), detecting pseudoaneurysms, vascular injuries, and determining if angioembolization rather than surgery is needed. 4

• If patient becomes unstable during or while awaiting CT, abort imaging immediately and proceed directly to operating room based on positive FAST findings. 4, 2

If FAST is Negative:

• Still proceed to CT with IV contrast in stable patients with penetrating abdominal trauma, as FAST has limited sensitivity for hollow viscus injury, mesenteric injury, and retroperitoneal bleeding. 5, 6

• Knife injuries are typically low-energy with tissue damage only along the wound tract, but depth of penetration and specific organ involvement require CT characterization. 1

Why Other Options Are Inappropriate

DPL (Diagnostic Peritoneal Lavage):

• More invasive and time-consuming than FAST with no advantage in this stable patient. 1
• DPL has been largely replaced by FAST and CT in modern trauma algorithms. 1

CT Scan Immediately:

• While CT is the definitive imaging, FAST should be performed first as it is faster, bedside, and helps triage the urgency of CT versus immediate surgery. 1
• CT is appropriate as the next step after positive FAST in stable patients. 4

Immediate Laparotomy:

• Not indicated in hemodynamically stable patients without confirmed intra-abdominal catastrophe. 1
• Immediate laparotomy is reserved for hypotensive patients (SBP <90 mmHg) with positive FAST who cannot be stabilized with resuscitation. 1
• This patient's BP of 116/58 mmHg indicates hemodynamic stability, making diagnostic imaging appropriate before surgical intervention. 1

Critical Caveats

• Monitor hemodynamic status continuously - any deterioration (SBP <90 mmHg, tachycardia >110 bpm) mandates immediate surgical exploration if FAST is positive. 1, 2

• The mild hypoxemia (O2 92%) requires supplemental oxygen and consideration of pneumothorax on extended FAST (e-FAST), as stab wounds to central abdomen can involve the thoracoabdominal transition. 6, 7

• Every 10-minute delay from admission to laparotomy in unstable patients increases mortality, emphasizing the importance of continuous reassessment during the diagnostic workup. 4, 2

• FAST provides a "yes or no" answer for free fluid presence but does not quantify bleeding or identify specific organ injuries - this requires CT in stable patients. 6