While the FAST scan has been validated only in hemodynamically unstable blunt trauma patients, it has become a standard tool in the trauma bay and Emergency Department (ED) in most trauma patients.4 It is now considered an adjunct to the primary survey in Advanced Trauma Life Support (ATLS) guidelines, ninth edition.5 It has also come into use for hemodynamically stable patients and penetrating trauma in the deployed setting where CT scans are not readily available. If positive, these scans provide quick information that can aid trauma surgeons in triaging patients, either to the Operating Room (OR) or to further imaging. FAST in combat trauma has a sensitivity of only 56% and specificity of 98%.6 Routine use of the FAST in trauma patients allows for a consistent evaluation strategy while maintaining the skills of providers. A negative FAST cannot be relied upon to rule out injury, especially in penetrating trauma.

Diagnostic Peritoneal Lavage (DPL)

In the absence of a CT scanner, DPL should be considered in determining need for laparotomy in trauma patients. It has largely been supplanted by the FAST exam (and is considered an optional skill in the current edition of ATLS). DPL remains the most sensitive test for hollow viscus injury and mesenteric injury, and retains its usefulness in the unstable patient with a negative or equivocal FAST exam. DPL is 100% accurate for intra abdominal injury in these patients.7 One must consider the additional time that this diagnostic test may require, and should not delay immediate surgical intervention in patients that have mechanisms concerning for intra-abdominal trauma and remain unstable despite resuscitative measures.8

Role of the Radiologist

At the Role 3, properly trained providers including radiologists, surgeons and emergency physicians, can perform and interpret FAST scans in the ED on a hand held portable US device. The utility of radiologists performing the exams would be to free up emergency providers and surgeons to either perform other assessments or interventions, or care for additional patients in the trauma bays. While in the trauma bay, the radiologist would also be available to provide preliminary interpretations of the portable chest x-ray/pelvis exams on the digital portable machines. However, once CT scans begin to be obtained on the trauma patients, the emergency physicians and surgeons would primarily perform the FAST scans and interpret plain radiographs at the bedside.

Equipment

The examination is performed with a portable hand-held machine most commonly using a standard 3-7 MHz curved array US probe. A phased array probe is also acceptable, and occasionally is preferred if cardiac or pulmonary imaging is necessary. Real-time imaging is performed without the necessity of saving static images.

Standard Examination

The standard FAST examination is focused on evaluating for the presence of free intraperitoneal fluid in:

1. The right upper quadrant between the liver and kidney,

2. The left upper quadrant between the spleen and kidney, and;

3. The pelvis at the level of the bladder.

4. An evaluation for cardiac activity and hemopericardium/tamponade should also be performed by placing the probe in the subxiphoid location and aiming towards the patients left shoulder.4

Additional Examinations

The cardiac portion of the exam can rapidly identify cardiac injury, evaluate cardiac function and give information about the success of resuscitation.9 In the case of massive exsanguination; the examination should be rechecked for free fluid after blood is given. A clot identified within a ventricle indicates prolonged asystole and may aid in the decision to terminate efforts. Pneumothorax or hemothorax may also be identified by placing the probe along the chest wall and looking for the presence of lung sliding. Loss of sliding implies the possible presence of a pneumothorax.10