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The Focused Assessment with Sonography for Trauma (FAST) exam aids in the diagnosis of abnormal fluid or air collection in the torso
The Focused Assessment with Sonography for Trauma (FAST) exam aids in the diagnosis of abnormal fluid or air collection in the torso. The FAST exam is suitable for both blunt and penetrating injuries in people of all ages.
What are the pros and cons of the FAST exam?
Advantages
- Can be completed quickly sometimes in less than one minute
- Can be repeated as many times as necessary.
- Helps monitor patient health or detect the progression of injuries
- Does not use ionizing radiation like a computed tomography (CT) scan (an important consideration in susceptible populations such as children and pregnant women)
- Results in faster transport of hemodynamically unstable patients to the operating room and earlier use of blood transfusion, hence accelerating patient care
Disadvantages
- User-dependent, meaning an experienced user may detect a small amount of free fluid that a beginner user might miss
- Cannot detect organ damage right away and instead examines the presence or absence of free fluid
- Does not directly measure the retroperitoneum and therefore not intended to estimate potential blood loss in that area
- Limited by variables such as obesity, intestinal gas, and subcutaneous emphysema
- May wrongly interpret pre-existing medical problems (ascites, pleural effusions, and fluid from a burst ovarian cyst) as the result of trauma, requiring surgical intervention when none was necessary
- May wrongly attribute minor physiologic free fluid, such as that seen in a female patient of childbearing age, to trauma
- Negative results do not rule out significant harm; negative results in an unstable patient may require further resuscitation in the trauma center until the patient is stable enough for a CT scan
When is the FAST exam used for traumatic torso injuries?
Damage from trauma is one of the indications for a FAST exam of the torso, but it is not the sole indication.
There are no categorical contraindications, but FAST exams have limitations, including the inability to detect free fluid in some injured children, patients with mesenteric injury, and patients with isolated penetrating peritoneal injury. The presence of fluid in the peritoneum for physiological causes, such as ovarian cyst rupture, as well as pathologic ones, such as individuals with ascites, may limit the diagnosis of free traumatic fluid in the peritoneum.
Free fluid from other sources apart from trauma, pericardial cysts, pre-existing pericardial fluid, and pre-existing pleural disease are all considered contraindications for a FAST exam in traumatic torso injury.
What does the research say about the FAST exam in traumatic torso injuries?
Emergency ultrasonography has been shown in studies to reduce the number of CT scans in traumatic abdominal injuries. There has, however, been no systematic study of the FAST exam's efficacy in penetrating torso trauma.
According to this research, the FAST exam can identify free intraperitoneal blood pericardial free fluid after penetrating torso trauma. The prevalence of a positive FAST exam after penetrating injuries, on the other hand, ranged from 24.2%-56.3%. The FAST exam is a highly specific (94.1%-100%) but not very sensitive (28.1%-100%) diagnostic tool for penetrating trauma.
To summarize, a positive FAST exam indicates a high risk of intra-abdominal damage and should necessitate an exploratory laparotomy. A negative initial FAST exam after penetrating trauma, on the other hand, should elicit further diagnostic tests.
The FAST exam in pediatric emergency care does not improve the care of stable patients with traumatic torso trauma, increases the detection of missed intra-abdominal injuries or reduces the length of stay in the emergency department or hospital charges. The study's findings do not support the usual use of the FAST exam in the pediatric emergency department.