A 56-year-old man is brought to the emergency department 25 minutes after he was involved in a high-speed motor vehicle collision where he was the unrestrained passenger. He has severe lower abdominal and pelvic pain. On arrival, he is alert and oriented. His pulse is 95/min, respirations are 22/min, and blood pressure is 106/62 mm Hg. Examination shows severe tenderness to palpation over the lower abdomen and over the left anterior superior iliac spine. There is no limb length discrepancy. Application of downward pressure over the pelvis shows no springy resistance or instability. Rectal examination is unremarkable. A focused assessment with sonography shows no free fluid in the abdomen. There is no blood at the urethral meatus. Placement of a Foley catheter shows gross hematuria. An x-ray of the pelvis shows a fracture of the left pelvic edge. Which of the following is the most appropriate next step in management?

External fixation of the pelvis

A 41-year-old man is admitted to the emergency room after being struck in the abdomen by a large cement plate while transporting it. On initial assessment by paramedics at the scene, his blood pressure was 110/80 mm Hg, heart rate 85/min, with no signs of respiratory distress. On admission, the patient is alert but in distress. He complains of severe, diffuse, abdominal pain and severe weakness. Vital signs are now: blood pressure 90/50 mm Hg, heart rate 96/min, respiratory rate 19/min, temperature 37.4℃ (99.3℉), and oxygen saturation of 95% on room air. His lungs are clear on auscultation. The cardiac exam is significant for a narrow pulse pressure. Abdominal examination reveals a large bruise over the epigastric and periumbilical regions. The abdomen is distended and there is diffuse tenderness to palpation with rebound and guarding, worst in the epigastric region. There is hyperresonance to percussion in the epigastric region and absence of hepatic dullness in the right upper quadrant. Aspiration of the nasogastric tube reveals bloody contents. Focused assessment with sonography for trauma (FAST) shows free fluid in the pelvic region. Evaluation of the perisplenic and perihepatic regions is impossible due to the presence of free air. Aggressive intravenous fluid resuscitation is administered but fails to improve upon the patient’s hemodynamics. Which of the following is the next best step in management?

Diagnostic peritoneal lavage (DPL)

A 24-year-old man is brought by ambulance to the emergency department after a motor vehicle accident. He was the front seat driver in a head on collision. He is currently unconscious. The patient’s past medical history is only notable for an allergy to amoxicillin as he developed a rash when it was given for a recent upper respiratory infection 1 week ago. Otherwise, he is a college student in good health. The patient is resuscitated. A FAST exam is notable for free fluid in Morrison’s pouch. An initial assessment demonstrates only minor bruises and scrapes on his body. After further resuscitation the patient becomes responsive and begins vomiting. Which of the following is the most likely diagnosis?

Rupture of the inferior vena cava

A 17-year-old adolescent male is brought to the emergency department by fire and rescue after being struck by a moving vehicle. The patient reports that he was running through his neighborhood when a car struck him while turning right on a red light. He denies any loss of consciousness. His temperature is 99.0°F (37.2°C), blood pressure is 88/56 mmHg, pulse is 121/min, respirations are 12/min, and SpO2 is 95% on room air. The patient is alert and oriented to person, place and time and is complaining of pain in his abdomen. He has lacerations on his face and extremities. On cardiac exam, he is tachycardic with normal S1 and S2. His lungs are clear to auscultation bilaterally, and his abdomen is soft but diffusely tender to palpation. The patient tenses his abdomen when an abdominal exam is performed. Bowel sounds are present, and he is moving all 4 extremities spontaneously. His skin is cool with delayed capillary refill. After the primary survey, 2 large-bore IVs are placed, and the patient is given a bolus of 2 liters of normal saline. Which of the following is the best next step in management?

Focused Abdominal Sonography for Trauma (FAST) exam

A 33-year-old man is brought to the emergency department because of trauma from a motor vehicle accident. His pulse is 122/min and rapid and thready, the blood pressure is 78/37 mm Hg, the respirations are 26/min, and the oxygen saturation is 90% on room air. On physical examination, the patient is drowsy, with cold and clammy skin. Abdominal examination shows ecchymoses in the right flank. The external genitalia are normal. No obvious external wounds are noted, and the rest of the systemic examination values are within normal limits. Blood is sent for laboratory testing and urinalysis shows 6 RBC/HPF. Hematocrit is 22% and serum creatinine is 1.1 mg/dL. Oxygen supplementation and IV fluid resuscitation are started immediately, but the hypotension persists. The focused assessment with sonography in trauma (FAST) examination shows a retroperitoneal fluid collection. What is the most appropriate next step in management?

Take the patient to the OR for an exploratory laparotomy

Perform an MRI scan of the abdomen and pelvis

CT of the abdomen and pelvis with contrast

Obtain a retrograde urethrogram

Perform a diagnostic peritoneal lavage

A 35-year-old male is brought into the emergency department for a trauma emergency. The emergency medical services states that the patient was wounded with a knife on his upper left thigh near the inguinal ligament. Upon examination in the trauma bay, the patient is awake and alert. His physical exam and FAST exam is normal other than the knife wound. Large bore intravenous lines are inserted into the patient for access and fluids are being administered. Pressure on the knife wound is being held by one of the physicians with adequate control of the bleeding, but the physician notices the blood was previously extravasating in a pulsatile manner. His vitals are BP 100/50, HR 110, T 97.8, RR 22. What is the next best step for this patient?

Coagulation studies and blood typing/crossmatch

Tourniquet of proximal lower extremity

A 56-year-old man is brought to the emergency department after falling 16 feet from a ladder. He has severe pain in both his legs and his right arm. He appears pale and diaphoretic. His temperature is 37.5°C (99.5°F), pulse is 120/min and weak, respirations are 26/min, and blood pressure is 80/50 mm Hg. He opens his eyes and withdraws in response to painful stimuli and makes incomprehensible sounds. The abdomen is soft and nontender. All extremities are cold, with 1+ pulses distally. Arterial blood gas analysis on room air shows: pH 7.29 PCO2 33 mm Hg PO2 65 mm Hg HCO3- 15 mEq/L A CT scan shows displaced fractures of the pelvic ring, as well as fractures of both tibiae, the right distal radius, and right proximal humerus. The patient undergoes emergent open reduction and is admitted to the intensive care unit. Which of the following best indicates inadequate fluid resuscitation?

Urine output of 25 mL in 3 hours

Capillary refill time of 3 seconds

Focused Assessment with Sonography in Trauma (FAST) for USMLE Step 3: High-Yield Surgery Lessons

FAST Fundamentals - Trauma's First Look

Goal: Rapid bedside ultrasound to detect free fluid (hemoperitoneum, hemopericardium) in hypotensive trauma patients.
Core Views (4 Ps):
- Pericardial (subxiphoid)
- Perihepatic (Morison's Pouch)
- Perisplenic
- Pelvic (suprapubic)
eFAST adds bilateral anterior thoracic views to screen for pneumothorax.

eFAST scan windows on a torso

⭐ FAST is highly specific for intraperitoneal fluid but can miss bowel/mesenteric injuries and retroperitoneal bleeds.

The 4 Views - A Quick Tour

A standardized sequence to rapidly identify hemoperitoneum or pericardial effusion.

1. RUQ (Hepatorenal / Morison's Pouch):
- Probe at right mid-axillary line (8th-11th intercostal space).
- Visualizes potential space between liver and right kidney.
⭐ Most sensitive view for intraperitoneal free fluid in a supine patient.
2. Subxiphoid (Pericardial):
- Probe inferior to xiphoid, aimed at the left shoulder.
- Crucial for identifying pericardial effusion/tamponade.
3. LUQ (Splenorenal):
- Probe at left posterior-axillary line (6th-9th intercostal space).
- Examines the space between the spleen and left kidney.
4. Suprapubic (Pelvic):
- Probe superior to pubic symphysis (transverse & sagittal planes).
- Visualizes rectovesical pouch (males) or Pouch of Douglas (females).

FAST exam probe positions and corresponding sonoanatomy

Interpreting Findings - Fluid, Air, & Action

FAST exam: Free fluid in Morison's pouch

Fluid (Blood): Appears anechoic (black). Accumulates in dependent areas.
- Key sites: Perihepatic (Morison's pouch), perisplenic, pelvic (Pouch of Douglas), pericardial.
Pneumothorax (eFAST):
- Present: Normal "lung sliding" (shimmering pleura) & "comet tail" artifacts.
- Absent: No lung sliding; "stratosphere" or "barcode" sign on M-mode.

⭐ In a hemodynamically stable patient, a positive FAST doesn't automatically mean surgery. A follow-up CT scan is crucial to quantify the volume of hemoperitoneum and grade the solid organ injury, guiding potential non-operative management.

Clinical Algorithm - The Decision Tree

⭐ A key limitation: FAST does not reliably visualize retroperitoneal, diaphragmatic, or bowel injuries. A negative FAST in a stable patient with a high-risk mechanism or persistent abdominal pain still warrants a CT scan.

The FAST exam is a rapid bedside ultrasound to detect hemoperitoneum or pericardial effusion in trauma.

It assesses four key windows: hepatorenal (Morison's pouch), splenorenal, subxiphoid (pericardial), and suprapubic (pelvic).

A positive FAST in an unstable patient is an indication for an immediate exploratory laparotomy.

Key limitation: It has poor sensitivity for retroperitoneal, solid organ, or diaphragmatic injuries.

For stable patients, a CT scan is the gold standard, especially if the FAST is equivocal or negative with high suspicion.

The eFAST adds bilateral thoracic views to detect pneumothorax or hemothorax.

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