What is the most appropriate initial step in managing a motorcycle accident victim with severe pelvic and back pain, transient hypotension, and free fluid in the lower abdomen on Focused Assessment with Sonography for Trauma (FAST), currently stable with a blood pressure of 100/60?

Management of Trauma Patient with Positive FAST and Borderline Hemodynamic Status

For this motorcycle trauma patient with positive FAST, severe pelvic/back pain, and borderline blood pressure (100/60), the most appropriate initial step is pelvic X-ray (Option A) to rapidly identify pelvic fractures that may be the source of ongoing hemorrhage, followed immediately by CT abdomen/pelvis with IV contrast if the patient remains stable. 1, 2

Hemodynamic Status Assessment

This patient occupies a critical gray zone requiring careful interpretation:

• Blood pressure of 100/60 mmHg represents borderline stability (hemodynamic stability is traditionally defined as systolic BP ≥90 mmHg), but the history of transient hypotension requiring fluid resuscitation indicates ongoing hemorrhage risk 1
• The patient required a 500 mL NS bolus for transient hypotension in the ambulance, suggesting active bleeding that temporarily responded to resuscitation 1
• This clinical picture represents a "responder" who may deteriorate rapidly, requiring immediate identification of the bleeding source 1, 2

Rationale for Pelvic X-ray First

In patients with suspected severe pelvic trauma who are hemodynamically unstable or require urgent interventions to stabilize vital signs, pelvic X-ray should be obtained immediately upon arrival 1:

• Pelvic fractures are a major source of life-threatening hemorrhage in trauma patients with positive FAST and can cause massive retroperitoneal bleeding that appears as free fluid on ultrasound 1
• The combination of severe pelvic/back pain, positive FAST, and borderline hemodynamics strongly suggests pelvic fracture with active bleeding 1
• Pelvic X-ray can be obtained in 1-2 minutes at bedside without transporting the patient, allowing rapid diagnosis and immediate application of definitive hemorrhage control measures 1
• If a pelvic fracture is identified, external pelvic compression with a binder can be applied immediately as a life-saving temporizing measure while preparing for definitive management 1

Why Not the Other Options

Option B (Retrograde urethrogram) is incorrect because:

• Urethral injury evaluation is not the priority in a patient with borderline hemodynamics and positive FAST 1
• Retrograde urethrogram is indicated when urethral injury is specifically suspected (blood at meatus, high-riding prostate, inability to void), but does not address the immediate life-threatening hemorrhage 3

Option C (CT abdomen/pelvis) is the correct next step ONLY if the patient remains hemodynamically stable after pelvic X-ray 1, 2:

• For hemodynamically stable patients, CT provides superior information about specific organ injuries and can guide operative versus non-operative management 2, 4
• However, this patient's borderline status (BP 100/60 after requiring fluid resuscitation) mandates rapid bedside assessment first 1, 2
• The American College of Radiology acknowledges that some trauma systems now perform whole-body CT while continuing resuscitation regardless of hemodynamic status, but emphasize that "the degree of hemodynamic instability and distance to the CT scanner should be accounted for" 1
• If pelvic X-ray is negative and the patient remains stable, proceed immediately to CT with IV contrast 1, 2

Option D (Back MRI) is completely inappropriate because:

• MRI has no role in the acute management of trauma patients with active bleeding 1
• MRI requires prolonged imaging time (30-60 minutes) and is contraindicated in unstable patients 1

Critical Management Algorithm

1. Obtain pelvic X-ray immediately at bedside (1-2 minutes) 1
2. If pelvic fracture identified: Apply pelvic binder around the greater trochanters immediately, activate massive transfusion protocol, and prepare for angiographic embolization or surgical intervention 1
3. If pelvic X-ray negative and patient remains stable (BP ≥100 systolic): Proceed immediately to CT abdomen/pelvis with IV contrast to identify the source of free fluid 1, 2
4. If patient deteriorates at any point (BP <90 systolic despite resuscitation): Abort imaging and proceed directly to operating room for damage control surgery 2, 4

Key Clinical Caveats

Continuous reassessment is mandatory 2, 4:

• Every 10-minute delay from admission to definitive hemorrhage control in unstable patients increases mortality by approximately 1% every 3 minutes 2
• The patient's response to initial fluid resuscitation determines the next step: responders can proceed to CT, transient responders need immediate hemorrhage control, and non-responders require immediate surgery 1, 2

FAST limitations in this scenario 1:

• Positive FAST indicates free fluid but does not differentiate between intraperitoneal blood from solid organ injury versus retroperitoneal hemorrhage from pelvic fracture 1
• FAST has a negative predictive value of 97% in patients with shock, but a positive result requires source identification 1
• Retroperitoneal hematoma from pelvic fracture can generate intra-abdominal effusion visible on FAST 1

Pelvic stabilization is critical 1:

• External pelvic compression should be applied as soon as pelvic fracture is identified, as it can reduce pelvic volume by up to 30% and tamponade venous bleeding 1
• Pelvic binders must be placed around the greater trochanters to be effective 1