Focused Assessment with Sonography in Trauma (FAST): An Overview

Traumatic injuries are one of the leading causes of death, and intraperitoneal bleeds occur in approximately 12% of blunt traumas [1]. A quick assessment of trauma and detection of intraperitoneal fluid is increasingly essential in trauma patients’ assessment. The implementation of point-of-care ultrasound (POCUS) has had a significant impact on patient management, especially in a trauma setting. POCUS is easy to use at the bedside, non-invasive and inexpensive.

The Focused Assessment with Sonography in Trauma (FAST) is an ultrasound protocol used to assess hemoperitoneum and hemopericardium [2]. The FAST protocol is sensitive and specific for detecting intraperitoneal free fluid. According to previous studies, sensitivity ranges from 75-100%, and specificity ranges from 88-100% [3]. The FAST exam is rapid and can be completed in less than 5 minutes. It also has multiple advantages, including decreased time to interventions like surgery and length of stay at the hospital [4]. The Extended FAST (eFAST) protocol, which involves examinations of each hemithorax for hemothorax and pneumothoraces, has recently been introduced by several institutions [2].

Regions Examined

The FAST exam assesses the pericardium and multiple potential spaces within the peritoneal cavity for free fluid. The patient is often assessed in the supine position.

The right flank or right upper quadrant (RUQ) view assesses the hepatorenal recess (also known as Morrison’s pouch), as well as the right paracolic gutter, the hepato-diaphragmatic area, and the caudal edge of the left liver lobe [2]. The pericardial view, also known as the subcostal or the subxiphoid, is usually assessed next. The liver is commonly used as a sonographic window of the heart to evaluate pericardium. Ultrasound can detect little pericardial fluid with sensitivity and specificity approaching 100% [5]. The pericardial view also helps to differentiate between pleural and pericardial effusions and visualize right ventricular collapse during diastole [2]. Next, the left upper quadrant (LUQ) is used to visualize the splenorenal recess, the subphrenic space and the left paracolic gutter. If the eFAST protocol is being conducted, the RUQ and LUQ views are also used to examine the left and right hemithorax. Lastly, the pelvic or the suprapubic view is used to assess for free fluid in the rectovesical pouch in males and rectouterine and vesicouterine pouches in women [2]. The bladder acts as a sonographic window for this view.

Complications

While there are no complications related to the FAST exam itself, the use of ultrasound does have some limitations, one of which is the requirement for at least 150-200 cc of intraperitoneal fluid for an ultrasound to be able to detect. This can lead to false negatives when free fluid is in fact present [6]. False positives in the FAST exam may also occur and can be due to the presence of ascites, pre-existing pleural or pericardial effusions unrelated to the trauma, ruptured ovarian cysts or ruptured ectopic pregnancies [2]. Healthcare workers should be aware that POCUS and the FAST protocol have limitations dependent on the provider’s experience and the patient’s body habitus.   

Further Reading and Free Online Course

References

  1. Poletti, P. A., Mirvis, S. E., Shanmuganathan, K., Takada, T., Killeen, K. L., Perlmutter, D., Hahn, J., & Mermillod, B. (2004). Blunt abdominal trauma patients: can organ injury be excluded without performing computed tomography?. The Journal of Trauma57(5), 1072–1081. https://doi.org/10.1097/01.ta.0000092680.73274.e1
  2. Bloom, B. A., & Gibbons, R. C. (2020). Focused Assessment with Sonography for Trauma. https://www.ncbi.nlm.nih.gov/books/NBK470479/
  3. Brenchley, J., Walker, A., Sloan, J. P., Hassan, T. B., & Venables, H. (2006). Evaluation of focussed assessment with sonography in trauma (FAST) by UK emergency physicians. Emergency Medicine Journal23(6), 446–448. https://doi.org/10.1136/emj.2005.026864
  4. Melniker, L. A., Leibner, E., McKenney, M. G., Lopez, P., Briggs, W. M., & Mancuso, C. A. (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 Medicine48(3), 227–235. https://doi.org/10.1016/j.annemergmed.2006.01.008
  5. Mandavia, D. P., Hoffner, R. J., Mahaney, K., & Henderson, S. O. (2001). Bedside echocardiography by emergency physicians. Annals of emergency medicine38(4), 377–382. https://doi.org/10.1067/mem.2001.118224
  6. Von Kuenssberg Jehle, D., Stiller, G., & Wagner, D. (2003). Sensitivity in detecting free intraperitoneal fluid with the pelvic views of the FAST exam. The American journal of emergency medicine21(6), 476–478. https://doi.org/10.1016/s0735-6757(03)00162-1
Cite this article as: Maryam Bagherzadeh, Canada, "Focused Assessment with Sonography in Trauma (FAST): An Overview," in International Emergency Medicine Education Project, September 20, 2021, https://iem-student.org/2021/09/20/sonography-in-trauma-fast/, date accessed: October 18, 2021

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