FAST and eFAST protocols: diagnostic techniques to be mastered in emergency medicine

In emergency medicine, rapid and accurate diagnosis is essential for optimal patient care. The FAST(Focused Assessment with Sonography for Trauma) and eFAST(extended FAST) protocols are rapid, non-invasive diagnostic explorations that have revolutionized the diagnostic and prognostic approach to the management of trauma patients. They are based on the use of targeted ultrasound, enabling crucial information to be obtained in real time.

‍

Definition and indications of the FAST and eFAST protocols

The FAST protocol was developed in the early 1990s for the rapid assessment of patients with abdominal trauma. It consists of a targeted ultrasound examination to detect the presence of fluid effusions (blood or free fluid) in the peritoneal cavities. The main aim is to detect life-threatening internal bleeding and guide therapeutic management.

The eFAST protocol, introduced in the early 2000s, is an extension of the FAST protocol. In addition to the areas explored by FAST, it includes assessment of the lungs and heart. eFAST is therefore indicated in situations of polytrauma or abdomino-thoracic trauma, acute respiratory distress or hemorrhagic shock.

‍

FAST and eFAST protocols and steps

Using a low-frequency convex probe (2-5 MHz), the FAST protocol focuses on four anatomical exploration zones, corresponding to specific ultrasound sections:

1. Section through the right upper quadrant of the abdomen:

This is a longitudinal section at the level of the last right ribs, with the probe positioned as posteriorly as possible. It allows visualization of the liver, right kidney and diaphragm, in order to assess the presence of peri-hepatic fluid or blood effusion (hemoperitoneum), in the hepato-renal space (Morrison's lodge) and right pleural or blood effusion (hemothorax).

2. Section through the left upper quadrant of the abdomen:

This longitudinal section is made at the level of the last left ribs, with the probe also positioned posteriorly. It visualizes the spleen, left kidney and diaphragm, and assesses the presence of fluid or blood effusion (hemoperitoneum) in the perisplenic area, splenorenal recess (Koller's pouch), and left pleural or blood effusion (hemothorax).

3. Suprapubic cuts :

Longitudinal and transverse sections above the pubic symphysis. These allow visualization of the bladder and, depending on the patient's sex, the uterus or prostate. The aim is to detect the presence of fluid or blood (hemoperitoneum) in the cul-de-sac of Douglas in women, or in the retrovesical region in men. 

4. Subxyphoid section :

For this cut, the probe is placed under the xiphoid process, oriented towards the patient's head with a slight downward inclination. It is used to assess the presence of free fluid or blood (hemopericardium) in the pericardium, as well as to detect signs of hemorrhagia in the upper intra-abdominal region, particularly at the level of the liver and diaphragm.

The eFAST protocol, which, depending on the school, can be performed with either a phased array probe (1-5 MHz), a high-frequency linear probe (5-12 MHz) or even a low-frequency convex probe (2-5 MHz), adds assessment of the lungs bilaterally to detect fluid/blood effusion (hemothorax) or gas effusion (pneumothorax):

5. Lung sections :

These longitudinal sections are taken in the 2nd - 3rd intercostal space, on the mid-clavicular line, on either side of the thorax. They are used to assess the lungs for signs of pneumothorax or fluid or blood effusion (hemothorax).

‍

Real-life applications of the FAST and eFAST protocols - what the literature says

The FAST and eFAST protocols have demonstrated their usefulness in many clinical situations. 

A retrospective study published in the journal Shock[1] assessed the usefulness of the FAST protocol in 107 children with abdominal trauma. The results showed that FAST had a sensitivity of 88% and a specificity of 97% for detecting intra-abdominal lesions requiring surgical intervention[2].

Another prospective study published in the Journal of Trauma and Acute Care Surgery evaluated the usefulness of eFAST in 200 patients with penetrating trunk injuries. The results showed that eFAST had a sensitivity of 92% and a specificity of 98% for detecting thoracic and abdominal injuries requiring surgical intervention.

With regard to dyspnoea, a study published in theAmerican Journal of Respiratory and Critical Care Medicine [3] assessed the usefulness of thoracic ultrasound (included in eFAST) in 150 patients presenting with acute dyspnoea. The results showed that thoracic ultrasound had a sensitivity of 90% and a specificity of 98% for diagnosing the cause of dyspnea, compared with an initially established clinical diagnosis.

Finally, with regard to targeted ultrasound of the heart, a study published in Critical Care Medicine [4] assessed the usefulness of cardiac ultrasound (included in eFAST) in 20 patients with hemorrhagic shock. The results showed that cardiac ultrasound helped guide hemodynamic resuscitation by identifying patients responsive to volume expansion and detecting cardiac complications.

‍

The benefits of the FAST and eFAST protocols for practitioners

The FAST and eFAST protocols offer several advantages for practitioners:

• Speed: they provide essential diagnostic information in a matter of minutes, which is particularly useful in emergency situations.
• Non-invasive: unlike other imaging examinations (CT scan, MRI), ultrasound does not expose the patient to ionizing radiation, and does not require injection of a contrast medium.
• Reproducibility: They deliver the same reliable results, regardless of the practitioner performing the procedure. Because they are based on standardized protocols with few technical variations. 
• Portability: ultrasound equipment is increasingly compact and can be easily transported to the patient's bedside, improving pre-hospital care.
• Accessibility: ultrasound can be learned relatively quickly, and FAST and eFAST protocols can be performed by non-radiology specialists.

‍

Conclusion

The FAST and eFAST protocols are important diagnostic tools in emergency medicine, enabling trauma patients to be assessed quickly and efficiently. Thanks to their simplicity and reliability, they have helped improve patient management, reducing morbidity and mortality associated with trauma and organ failure.

However, a single FAST and eFAST examination can be misleading, especially if performed too early. Serial testing is therefore recommended to rule out false positives and false negatives [5]. It is crucial that practitioners are well trained in their use and integrate them into their daily diagnostic approach.

The echOpen O1 probe is a great choice if you practice FAST and eFAST protocols. Ultra-portable, affordable and easy to use, its compact design means you can carry it in your pocket right up to the patient's bedside or in pre-hospital situations. Its low cost makes it accessible to healthcare professionals and institutions alike. Finally, its connectivity with a simple smartphone makes it easy to share ultrasound images for remote interpretation.

‍

‍

‍

-

[1] Holmes JF Jr, Chan LS, Kuppermann N, et al. Blunt abdominal trauma in children: value of focused assessment with sonography for trauma (FAST). Shock. 2001;15(5):347-351. doi:10.1097/00024382-200105000-00003

[2] Kirkpatrick AW, Sirois M, Laupland KB, et al. Hand-held thoracic sonography for detecting post-traumatic pneumothoraces: The Extended Focused Assessment with Sonography for Trauma (EFAST). Journal of Trauma and Acute Care Surgery. 2004;57(4):688-695. doi:10.1097/01.ta.0000138437.35883.14

[3] Lichtenstein DA, Meziere G, Biderman P, et al. The role of ultrasound in the diagnosis of acute respiratory failure: the BLUE protocol. American Journal of Respiratory and Critical Care Medicine. 2008;178(2):188-195. doi:10.1164/rccm.200710-1492OC

[4] Volpicelli G, Elbarbary M, Blaivas M, et al. International evidence-based recommendations for point-of-care lung ultrasound. Intensive Care Medicine. 2012;38(4):577-591. doi:10.1007/s00134-012-2513-4

[5] Pancholi K, Patel S, Parikh R, Saxena AK.** Efficacy of Focused Assessment Sonography in Trauma (FAST) in Patients with Blunt Abdominal Trauma. *IRPMS*. 2017 Jan-Mar;2(5):1-8.

‍