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The use of focused ultrasonography has now become an extension of the physical examination of the trauma patient. Performed in the trauma room by properly trained and credentialed staff, it allows the timely diagnosis of potentially life-threatening haemorrhage and is a decision-making tool to help determine the need for transfer to the operating room, CT scanner or angiography suite.
Ultrasound was first utilised for the examination of trauma patients in the 1970s in Europe, where its qualities for being a noninvasive, rapid, safe, accurate and repeatable bedside assessment were first appreciated. It's uptake in North America and the United Kingdom did not occur until the 1990s. Since that time a considerable body of data has been produced to support its use in the assessment of the trauma patient.
Focused Assessment with Sonography for Trauma (FAST) is a limited ultrasound examination directed solely at identifying the presence of free intraperitoneal or pericardial fluid. In the context of traumatic injury, free fluid is usually due to haemorrhage and contributes to the assessment of the circulation.
The Focused Assessment with Sonography for Trauma is a rapid, bedside, ultrasound examination performed to identify intra-peritoneal haemorrhage or pericardial tamponade.
FAST examines four areas for free fluid:
- Perihepatic & hepato-renal space
FAST assessment is indicated in trauma patients who give a history of abdominal trauma, are hypotensive, or are unable to provide a reliable history because of impaired consciousness due to head injury or drugs. FAST is an adjunct to the ATLS primary survey and therefore follows the performance of the ABCs. The ultrasound machine should be immediately available in the trauma room and its use should not interfere with the on-going assessment and management of the patient.
Small, portable ultrasound machines are now available which are highly appropriate to the trauma room environment. Standard FAST assessment is carried out using a curvilinear 2.5 or 3.5MHz probe.
How to perform the FAST examination
The hepatorenal space (pouch of Rutherford-Morison) is the most dependent part of the upper peritoneal cavity and small amounts of intra-peritoneal fluid may collect in this region first. Blood shows as a hypoechoic black stripe between the capsule liver and the fatty fascia of the kidney. The probe is placed in the right mid- to posterior axillary line at the level of the 11th and 12th ribs.
|Probe position for RUQ||Hepatorenal view|
|No free fluid||Fluid in hepatorenal space|
The left upper quadrant examination visualises the spleen and perisplenic areas. The transducer is placed on the left posterior axillary line region between the 10th and 11th ribs.
|Probe position for LUQ|
|No free fluid||Perisplenic free fluid|
The pelvic examination visualises the cul-de-sac: the Pouch of Douglas in females and the rectovesical pouch in the male. It is the most dependent portion of the lower abdomen and pelvis, hence where fluid will collect. The transducer is placed midline just superior to the symphysis pubis.
|Probe position for pelvis|
|No free fluid||Pelvic free fluid|
Pericardial sub-xiphoid scan
The pericardial examination screens for fluid between the fibrous pericardium and the heart, and hence possible cardiac tamponade. The transducer is placed just to the left of the xiphisternum and angled upwards under the costal margin.
|Probe position for pericardium||Pericardial view|
|Normal pericardium||Pericardial fluid|