Focused assessment with sonography for trauma

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 abnormal vitals including low blood pressure and fast heart rate such as blood around the heart (pericardial effusion) or abdominal organs (hemoperitoneum) after trauma. 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). 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.

Before the evolution of ultrasound and its rapid availability in hospitals, surgeons and emergency physicians used Diagnostic Peritoneal Lavage (DPL) which is an invasive procedure to diagnose hemoperitoneum. In the 1990s the FAST exam using the ultrasound became widely popular after advancement in Europe that showed the specificity 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.

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. 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.