Focused assessment with sonography for trauma

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"FAST scan" redirects here. For the stroke-related mnemonic, see FAST (stroke). For Fast-scan television, see Amateur television.
Focused assessment with sonography in trauma, a.k.a. FAST
Ultrasound image of a normal spleen that may be seen in part of the eFAST
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Focused assessment with sonography in trauma (commonly abbreviated as FAST) is a rapid bedside ultrasound examination performed by surgeons, emergency physicians, and paramedics as a screening test for sources of abnomral vitals including low blood pressure and fast heart rate such as blood around the heart (pericardial effusion) or abdominal organs (hemoperitoneum) after trauma.[1][2] The exam can also be expanded through the extended FAST (E-FAST) which includes additional ultrasound views to assess for pneumothorax or blood in the lungs(hemothorax) .[3][4] FAST exam is a low risk and efficient test that may be useful prior to conducting more sensitive tests such as CT in a stable trauma patient. CT remains the gold standard for diagnosing free fluid, ruptures and lacerations.[5]

Before the evolution of ultrasound and it's rapid availability in hospitals, surgeons and emergency physicians used Diagnostic Peritoneal Lavage (DPL) which is an invasive procedure to diagnose hemoperitoenum.[5] In the 1990s the FAST exam using the ulstrasound became widely popular after advacement in Europe that showed the specificty around 98% while also allowing for faster and cheaper diagnosis of trauma patients, particularly unstable who may not be able to make it to the CT.[5]

The four classic areas that are examined for free fluid (blood) are the perihepatic space (including Morison's pouch or the hepatorenal recess), perisplenic space, pericardium, and the pelvis.[6] With this technique it is possible to identify the presence of moderate to large amounts of intraperitoneal or pericardial free fluid, which in the setting of trauma, will usually be due to bleeding.The FAST exam is poor at detecting smaller amounts of free fluid with the sensitivity of ultrasound around 85% with 150mL of fluid making it useful for quick evaluation of trauma patients but not the gold standard.[5]

Indications

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Reasons a FAST or eFAST would be performed would be:

  1. Blunt abdominal trauma [3]
  2. Penetrating abdominal trauma [3]
  3. Blunt thoracic trauma [3]
  4. Penetrating thoracic trauma [3]
  5. Undifferentiated shock/unexplained hypotension (low blood pressure)[3]
  6. Ectopic pregnancy [7]

Contraindications

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Since the FAST/E-FAST is performed with ultrasound, there is very little risk to the patient as ultrasounds only emit sound waves and record the echo to create a picture rather than radiation.[8] Therefore, there are few contraindications or harms to the patient. The most common relative contraindication would be delay of more accurate imaging or definitive care such as surgical intervention in the hemodynamically unstable patient.[3]

There are some limitations of the FAST exam including user error, early bleeding, retroperitoneal (posterior) bleeding and body habitus.[9]

Extended FAST

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The E-FAST allows for the assessment of a patient's lungs by adding vies of the lungs using sonography to the FAST exam. This allows for the detection of a collapsed lung known as a pneumothorax with the absence of normal ‘lung-sliding’ and ‘comet-tail’ artifact seen on the ultrasound. Compared with supine chest radiography, bedside sonography has superior sensitivity (49–99% versus 27–75%), similar specificity (95–100%), and can be performed in under a minute, this making it well suited to settings without immediate access to more accurate investigations such as CT scanning.[10] Several recent prospective studies have validated its use in the setting of trauma resuscitation, and have also shown that ultrasound can provide an accurate estimation of pneumothorax size.[11][12] Although radiography or CT scanning is generally feasible, immediate bedside detection of a pneumothorax confirms what are often ambiguous physical findings in unstable patients.[13] In addition, in the patient undergoing positive-pressure ventilation, the detection of an unknown pneumothorax prior to CT scanning may hasten treatment and subsequently prevent development of a tension pneumothorax, a deadly complication if not treated immediately, and deterioration while in the CT scanner.[14]

Components of the examination

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During a FAST exam typically a curvilinear probe is chosen due to its ability to obtain good images of organs and deeper areas.[15] When viewing the lungs in the E-FAST a linear probe is preferred due to the increase in frequency allowing better images of superficial organs.[15] Next the components of the exam include:

1. Right upper abdomen: Called the perihepatic area and views an area called Morison's pouch in between the liver and kidney.[15]

2.  Left upper abdomen: The perisplenic view that is the area between the spleen and the left kidney.[15]

3. Pelvic: Views of the bladder in 2 orientations allows for view of free fluid around the bladder or injury to the bladder from blunt trauma.[15]

4. Cardiac: Views are obtained subxiphoid which allow for viewing if there is fluid around the heart and its motion.[15]

In the E-FAST the lung views are added using the linear probe to determine if there is a collapsed lung(pneumothorax) or fluid in the lung (pleural effusion/hemothorax).[16]

Findings

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Lung sliding to rule out pneumothorax

E-FAST allows the emergency physician or a surgeon the ability to determine whether a patient has a pneumothorax, hemothorax, pleural effusion efficiently without needing CT scanners. The exam allows for visualization of the organs and spaces where free fluid may pool due to injury. Few radiographic signs are important in the visualization of fluid in a trauma. These include the stratosphere sign, the sliding or seashore sign, and the sinusoid sign.

Stratosphere sign or Barcode sign is an ultrasound finding usually in an E-FAST examination that shows a presence of a collapsed lung also known as a pneumothorax.[17] The sign is an imaging finding using a linear ultrasound probe in between the 4th and 5th rib in the anterior clavicular line using the motion tracing (M-Mode) of the machine.[17] This finding is seen in the "M-mode" tracing as pleura and lung being indistinguishable as a row of lines and is fairly reliable for diagnosis of a pneumothorax.[17] Even though the stratospheric sign can be an indication of pneumothorax its absence is not reliable to rule out pneumothorax as definitive diagnosis usually requires X-ray or CT of thorax.[18][19][20]

Seashore sign using M mode on ultrasound showing the moving lung and absence of pneumothorax

Seashore sign is another E-FAST finding in the lungs using "M-mode" that depicts the echogenicity of the lung next to the linear appearance of the visceral pleura that surrounds the lungs.[17][18] This sign is a normal finding indicating no pneumothorax.[17]

B-lines or "comet trails" are echogenic bright linear reflections beneath the pleura that are usually lost with any air between the probe and the lung tissue and therefore whose presence with seashore sign indicates absence of a pneumothorax.[18][20]

Sinusoid sign is another M-mode finding indicating presence of fluid in the lungs also known as a pleural effusion.[17][18] Due to the cyclical movement of the lung in inspiration and expiration, the motion-time tracing (M-mode) ultrasound shows a sinusoid appearance between the fluid and the line of tissue.[17][18] This finding indicates possible fluid in the lungs (pleural effusion), accumulation of debris from infection (empyema), blood in pleural space (hemothorax).[18][19]

Advantages

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FAST is less invasive than diagnostic peritoneal lavage which was previously used more frequently, involves no exposure to radiation and is cheaper compared to computed tomography (CT). However, compared with CT, FAST cannot accurately rule out life-threatening injuries and is of limited value in settings where CT is readily available.[21]

Numerous studies have shown FAST is useful in evaluating trauma patients.[22][23][24][25] It also appears to make emergency department care more efficient and improve access to critically ill patients.[26][27]

  • Negative FAST but full stomach[28]
  • Negative FAST but full stomach[28]
  • Negative FAST but full stomach[28]

Interpretation

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FAST Algorithm

FAST is most useful in trauma patients who are hemodynamically unstable to guide surgical interventions. A positive FAST result is defined as the appearance of a dark ("anechoic") strip in the dependent areas of the peritoneum indicating free fluid or blood. In the right upper quadrant this typically appears in Morison's Pouch (between the liver and kidney).[15] This location is most useful as it is the place where fluid will collect with a supine patient. In the left upper quadrant, blood may collect anywhere around the spleen (perisplenic space).[15] In the pelvis, blood generally pools behind the bladder (in the rectovesicular space).[15] A positive result suggests hemoperitoneum; often CT scan will be performed if the patient is stable[29] or if unstable will be taken for a laparotomy.

In those with a negative FAST result, a search for extra-abdominal sources of bleeding may still need to be performed. FAST cannot reliably rule out all bleeding or life-threatening injury including posterior sources or small amounts that cannot be detected by ultrasound.

The value of FAST in situations where there is rapid access to CT or surgical intervention is limited, as a positive FAST requires either further investigation in the stable patient, or an operation in the unstable patient. A negative FAST cannot rule out injury.

See also

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References

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  1. ^ "Ultrasound in Trauma - The FAST Exam Focused Assessment with Sonography in Trauma". www.sonoguide.com. Archived from the original on 2008-09-14.
  2. ^ "Austere and Prehospital Ultrasound – The College of Remote & Offshore Medicine". Retrieved 2024-03-06.
  3. ^ a b c d e f g Bloom, Benjamin A.; Gibbons, Ryan C. (2022). "Focused Assessment with Sonography for Trauma". StatPearls. StatPearls Publishing. PMID 29261902.
  4. ^ Mallinson, T (2024). Prehospital & Emergency Ultrasound: Logbook & Guide. London, England: Caladrius Press. ISBN 978-1917521062.
  5. ^ a b c d Savoia, Paulo; Jayanthi, Shri Krishna; Chammas, Maria Cristina (April 2023). "Focused Assessment with Sonography for Trauma (FAST)". Journal of Medical Ultrasound. 31 (2): 101–106. doi:10.4103/jmu.jmu_12_23. ISSN 0929-6441. PMC 10413405. PMID 37576415.
  6. ^ Savatmongkorngul, Sorravit; Wongwaisayawan, Sirote; Kaewlai, Rathachai (2017-07-26). "Focused assessment with sonography for trauma: current perspectives". Open Access Emergency Medicine. 9: 57–62. doi:10.2147/OAEM.S120145. PMC 5536884. PMID 28794661.
  7. ^ Boyd, Jeremy; Melton, Myles; Rupp, Jordan; Ferre, Robinson (2021). "Trauma ultrasound". The Atlas of Emergency Medicine (5th ed.). McGraw-Hill.
  8. ^ "Ultrasound". National Institute of Biomedical Imaging and Bioengineering.
  9. ^ Wang, Pei-Hsiu; Lin, Hao-Yang; Chang, Po-Yuan; Lien, Wan-Ching (July 2021). "Focused Assessment with Sonography for Trauma". Journal of Medical Ultrasound. 29 (3): 151–153. doi:10.4103/jmu.jmu_128_21. ISSN 0929-6441. PMC 8515623. PMID 34729321.
  10. ^ Kirkpatrick AW, Sirois M, Laupland KB, et al., J Trauma, 2004;57(2):288–95.
  11. ^ Zhang M, Liu ZH, Yang JX, et al., Crit Care, 2006;10(4):R112.
  12. ^ Blaivas M, Lyon M, Duggal SA, Acad Emerg Med, 2005;12(9):844–9.
  13. ^ Netherton, Stuart; Milenkovic, Velimir; Taylor, Mark; Davis, Philip J. (November 2019). "Diagnostic accuracy of eFAST in the trauma patient: a systematic review and meta-analysis". CJEM. 21 (6): 727–738. doi:10.1017/cem.2019.381. ISSN 1481-8035. PMID 31317856.
  14. ^ Davis JA, et al. Critical Diagnosis in Bedside Ultrasonography. Diagnostics & Imaging. 2007.
  15. ^ a b c d e f g h i Desai, N.; Harris, T. (February 2018). "Extended focused assessment with sonography in trauma". BJA Education. 18 (2): 57–62. doi:10.1016/j.bjae.2017.10.003. ISSN 2058-5357. PMC 7807983. PMID 33456811.
  16. ^ [1], Patel D, Lewis K, Peterson A, Hafez M. Extended Focused Assessment with Sonography for Trauma (EFAST) Exam. J Med Ins.; (299.6) doi:https://jomi.com/article/299.6
  17. ^ a b c d e f g Department of Radiodiagnosis, SLBS Medical College, Mandi (HP), India; Bhoil, Rohit; Ahluwalia, Ajay; Department of Radiodiagnosis, SLBS Medical College, Mandi (HP), India; Chopra, Rajesh; Department of CTVS, IGMC Shimla (HP), India; Surya, Mukesh; Department of Radiodiagnosis, SLBS Medical College, Mandi (HP), India; Bhoil, Sabina; Department of Cardiac Anaesthesia, IGMC Shimla (HP), India (2021-08-16). "Signs and lines in lung ultrasound". Journal of Ultrasonography. 21 (86): e225 – e233. doi:10.15557/JoU.2021.0036. PMC 8439137. PMID 34540277.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  18. ^ a b c d e f Christopher P. Holstege; Alexander B. Baer; Jesse M. Pines; William J. Brady (2011). Visual Diagnosis in Emergency and Critical Care Medicine. Wiley-Blackwell. pp. 95–7. ISBN 9781444397987.
  19. ^ a b Christoph T. Bolliger; F. J. F. Herth; P. Mayo; T. Miyazawa; J. Beamis (2009). Clinical chest ultrasound: from the ICU to the bronchoscopy suite. Karger Publishers. pp. 86–8. ISBN 9783805586429.
  20. ^ a b Steven G. Rothrock (M.D.) (2009). Tarascon Adult Emergency Pocketbook. Tarascon. p. 144.
  21. ^ Rozycki G, Shackford S (1996). "Ultrasound, what every trauma surgeon should know". J Trauma. 40 (1): 1–4. doi:10.1097/00005373-199601000-00001. PMID 8576968.
  22. ^ Dolich MO, McKenney MG, Varela JE, Compton RP, McKenney KL, Cohn SM (Jan 2001). "2,576 ultrasounds for blunt abdominal trauma". Journal of Trauma. 50 (1): 108–12. doi:10.1097/00005373-200101000-00019. PMID 11231679.
  23. ^ Farahmand N, Sirlin CB, Brown MA, Shragg GP, Fortlage D, Hoyt DB, Casola G (May 2005). "Hypotensive patients with blunt abdominal trauma: performance of screening US". Radiology. 235 (2): 436–43. doi:10.1148/radiol.2352040583. PMID 15798158.
  24. ^ Sirlin CB, Brown MA, Andrade-Barreto OA, Deutsch R, Fortlage DA, Hoyt DB, Casola G (Mar 2004). "Blunt abdominal trauma: clinical value of negative screening US scans". Radiology. 230 (3): 661–8. doi:10.1148/radiol.2303021707. PMID 14990832.
  25. ^ Moylan M, Newgard CD, Ma OJ, Sabbaj A, Rogers T, Douglass R (Oct 2007). "Association between a positive ED FAST examination and therapeutic laparotomy in normotensive blunt trauma patients". Journal of Emergency Medicine. 33 (3): 265–71. doi:10.1016/j.jemermed.2007.02.030. PMID 17976554.
  26. ^ Melniker LA, Leibner E, McKenney MG, Lopez P, Briggs WM, Mancuso CA (Sep 2006). "Randomized controlled clinical trial of point-of-care, limited ultrasonography for trauma in the emergency department: the first sonography outcomes assessment program trial". Annals of Emergency Medicine. 48 (3): 227–35. doi:10.1016/j.annemergmed.2006.01.008. PMID 16934640.
  27. ^ Ollerton JE, Sugrue M, Balogh Z, D'Amours SK, Giles A, Wyllie P (Apr 2006). "Prospective study to evaluate the influence of FAST on trauma patient management". Journal of Trauma. 60 (4): 785–91. doi:10.1097/01.ta.0000214583.21492.e8. PMID 16612298.
  28. ^ a b c "UOTW #18 - Ultrasound of the Week". Ultrasound of the Week. 17 September 2014. Retrieved 27 May 2017.
  29. ^ Scalea T, Rodriguez A, Chiu W, Brenneman F, Fallon W, Kato K, McKenney M, Nerlich M, Ochsner M, Yoshii H (1999). "Focused Assessment with Sonography for Trauma (FAST): results from an international consensus conference". Journal of Trauma. 46 (3): 466–72. doi:10.1097/00005373-199903000-00022. PMID 10088853.
Further reading
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