Procedures

Focused Assessment with Sonography in Trauma Procedure

Background

1. Definition
   • The purpose of the Focused Assessment with Sonography in Trauma Procedure (FAST) is to rapidly evaluate a trauma patient with ultrasound scan
     • FAST Scan can be completed within 5 minutes
2. Synopsis
   • Evaluation of blunt trauma with ultrasound (US) has been described > 30 years
     • Phrase first coined in 1996
     • Focus of exam is to detect free fluid
       • Hemopericardium / tamponade
       • Hemoperitoneum
     • Minimum amount of fluid detectable in FAST scan: 200-250 cc
     • Aids in determining need for emergent surgery
   • Solid organ injury detection is beyond scope of FAST
     • Solid organ injury can be inferred by hemoperitoneum
   • Suggestions
     • 5° of Trendelenburg improves sensitivity
     • Probe should be 3.5-5 MHz
     • Time to complete scan: 4-6 min
3. Sensitivity and Specificity
   • Sensitivity:
     • Hemoperitoneum: 82-98%
     • Parenchymal injury: 41-69%
     • Hemopericardium: 80-100%
     • Hemothorax: 96%
     • Predicting need for surgery for abdominal injury: 81-90%
   • Specificity:
     1. Hemoperitoneum: 88-100%
     2. Parenchymal injury: 88-100%
     3. Hemopericardium: 96.3-97%
     4. Hemothorax: 99%
     5. Predicting need for surgery for abdominal injury: 88-95%

Indications

1. Blunt trauma with suspected intraperitoneal injury
2. Blunt trauma with shock out of proportion to injuries
3. Blunt trauma in patient who is:
   • Unconscious
   • Paralyzed
   • Altered mental status
     • Intoxicated
   • About to be anesthetized for other injuries
     • Orthopedic

Contraindications

1. If it would delay/negatively impact a clinically obvious emergent operative intervention

Basic Views

1. Perihepatic (RUQ) (View image)
   • Assesses:
     • Hepatorenal interface and right chest (View image)
       • Hepatorenal interface = Morison's pouch (View image)
   • Probe in anterior axillary line over lower intercostal spaces (8-11)
   • Indicator toward patient's head and directed at right posterior axilla
   • Window should include liver, kidney, diaphragm interface (View image)
   • Look for fluid in Morison's pouch: anechoic (black) stripe
     • Minimum amount of fluid detectable in Morison's pouch:
       • 50-100cc in controlled studies
       • 250-400cc in 10% of ultrasonographers
       • 400-700c in all ultrasonographers
   • Look for fluid in the subdiaphragmatic space
   • Move probe cephalad to view above diaphragm, check for fluid
   • Move probe caudal to look in paracolic gutter for fluid
2. Perisplenic (LUQ)
   • Assesses:
     • The splenorenal recess: between inferior margin of spleen and inferior pole of left kidney
     • Splenorenal interface and left chest (View image)
   • Probe in anterior axillary line over lower intercostal spaces (8-11)
   • Indicator toward patient's head and directed at left posterior axilla
   • The spleen and kidney should be visualized from the diaphragm to the inferior tip of the spleen
     • Window should include spleen, kidney, diaphragm interface (View image)
   • Perisplenic window is technically more difficult than perihepatic
   • Look for fluid in splenorenal interface: anechoic (black) stripe (View image)
   • Look for fluid in subdiaphragmatic space
   • Move probe cephalad to view above diaphragm, check for fluid
   • Move probe caudal to look in paracolic gutter for fluid
3. Subxiphoid
   • Detects:
     • Fluid accumulates initially in the inferior-posterior portion of the pericardial space (supine trauma patient)
       • Pericardial fluid (View image)
   • Probe in epigastric/subxiphoid, aim indicator towards right arm
   • Aim footprint toward patient's right shoulder
   • Depress abdomen to get true subcostal view
   • This window should show left lobe of liver and 4 chambers of heart
   • If bowel gas is interfering
     • Shift probe to patient's right
     • Use liver as US window to heart
   • Look for fluid as anechoic stripe between hyperechoic pericardium (View image)
   • Look for RA and RV diastolic collapse: evidence of tamponade
4. Pelvic
   • Assesses:
     • Rectovesical/rectouterine space; most inferior-posterior reflection of peritoneum
     • Free fluid next to bladder (View image)
   • Probe in suprapubic midline abdomen just superior to pubic symphysis
   • Aim indicator towards patient's head
   • Rock transducer superior and inferior
   • Visualize the bladder
   • Look for fluid as anechoic stripe or space posterior/cephalad to bladder
   • In females look for fluid posterior to the uterus
5. EFAST
   • Incorporation of thoracic imaging coupled with FAST exam
     • Has been referred to as an Extended FAST exam (EFAST)
     • Assesses for the presence of a hemothorax or a pneumothorax
   • Hemothorax: best assessed by visualizing inferior-posterior pleural cavity (supine patient)
     • Often visualized in routine views of Morrison's pouch but may require moving US transducer superior one intercostal space
   • Pneumothorax: best assessed in supine patient with curvilinear, linear, or phased-array transducer
     • High-frequency linear transducer used to image vascular structures is ideal but not required
     • Place transducer on anterior chest wall in area bounded by anterior axillary line, clavicle, nipple, and sternum (about the 3rd or 4th interspace)
     • Start with transducer on midclavicular line between nipple and clavicle
     • Move transducer within area to obtain best image possible
     • Position transducer perpendicular to adjacent ribs to visualize intercostal space
       • Visualize interface between parietal and visceral pleura ⇒ hyperechoic white line
       • Visualize normal sliding of pleura during respirations (i.e., to-and-fro movement)
         • Known as “sliding-lung” sign (absent in a pneumothorax)
     • M-mode: “sea-shore” sign ⇒ normal chest wall-lung interface
       • Pneumothorax ⇒ horizontal echogenic lines ⇒ loss of "sea-shore" sign

Clinical Algorithms

1. FAST- Oriented Algorithm
   • FAST scan done on all patients
     • Hemodynamically STABLE
       • Negative FAST Scan
         • Serial Exams or CT scan
       • Positive FAST Scan
         • To OR / CT
     • Hemodynamically UNSTABLE
       • Negative FAST Scan
         • Other extra- abdominal source
         • DPL
       • Positive FAST Scan
         • To OR
2. Hemodynamics - Oriented Algorithm
   • Hemodynamically STABLE
     • YES
       • CT and/or Serial Exams (+/- FAST)
     • NO
       • FAST Scan Positive
         • YES
           • To OR for Laparotomy
         • NO
           • Other extra- abdominal source
           • DPL

References

1. In: Tintinalli JE, Ma OJ, et al; (eds). Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 9th ed., McGraw-Hill, 2020; Chapter 263
2. Reichman EF (ed). Reichman's Emergency Medicine Procedures, 3rd ed., McGraw-Hill Education, 2019; Chapter 8
3. Bloom BA, Gibbons RC. Focused Assessment eith Sonography for Trauma. StatPearls [Internet]. Available at: https://www.ncbi.nlm.nih.gov/books/NBK470479/. [Accessed May 2023]
4. Rowland-Fisher A, Reardon RF. Focused Assessment with Sonography in Trauma (FAST). ACEP online. Available at: https://www.acep.org/sonoguide/basic/fast. [Accessed May 2023]
5. Savatmongkorngul S, Wongwaisayawan S, Kaewlai R. Focused assessment with sonography for trauma: current perspectives. Open Access Emerg Med. Jun 20, 2017;9:57-62
6. Bode PJ, Niezen RA, van Vugt AB, Schipper J. Abdominal ultrasound as a reliable indicator for conclusive laparotomy in blunt abdominal trauma. J Trauma 1993;34(1):27-31
7. Scalea TM, Rodriguez A, Chiu WC, Brenneman FD, Fallon Jr. WF, Kato K, et al. Focused Assessment with Sonography for Trauma (FAST): results from an international consensus conference. J Trauma 1999;46(3):466-472
8. Ingeman JE, Plewa MC, Okasinski RE, King RW, Knotts FB. Emergency physician use of ultrasonography in blunt abdominal trauma. Acad Emerg Med 1996;3(10):931-937
9. Rozycki GS, Ochsner MG, Schmidt JA, Frankel HL, Davis TP, Wang D, et al. A prospective study of surgeon-performed ultrasound as the primary adjuvant modality for injured patient assessment. J Trauma 1995;39(3):492-498
10. Rose JS. Ultrasound in abdominal trauma. Emergency Medicine Clinics of North America, Aug 2004;22(3)

Contributor(s)

1. Ballarin, Daniel, MD
2. Ho, Nghia, MD

Updated/Reviewed: May 2023