Focused assessment with sonography for trauma
Encyclopedia
Focused Assessment with Sonography for Trauma (commonly abbreviated as FAST) is a rapid bedside ultrasound
examination performed by surgeon
s and emergency physician
s as a screening test for blood around the heart (pericardial tamponade) or abdominal organs (hemoperitoneum
) after trauma
.
The four areas that are examined for free fluid are the perihepatic space (also called Morison's pouch or the hepatorenal recess), perisplenic
space, pericardium
, and the pelvis. With this technique it is possible to identify the presence of intraperitoneal or pericardial free fluid. In the context of traumatic injury, this fluid will usually be due to bleeding.
with the absence of normal ‘lung-sliding’ and ‘comet-tail’ artifact (seen on the ultrasound screen). Compared with supine chest radiography, with CT or clinical course as the gold standard, bedside sonography has superior sensitivity
(49–99 versus 27–75%), similar specificity
(95–100%), and can be performed in under a minute. Several recent prospective
studies have validated its use in the setting of trauma resuscitation, and have also shown that ultrasound can provide an accurate estimation of pneumothorax size. Although radiography or CT scanning is generally feasible, immediate bedside detection of a pneumothorax confirms what are often ambiguous physical findings in unstable patients, and guides immediate chest decompression
. In addition, in the patient undergoing positive-pressure ventilation, the detection of an otherwise ‘occult’ pneumothorax prior to CT scanning may hasten treatment and subsequently prevent development of a tension pneumothorax, a deadly complication if not treated immediately, and deterioration in the radiology
suite (in the CT scanner).
, involves no exposure to radiation and is cheaper compared to computed tomography
, but achieves a similar accuracy.
Numerous studies have shown FAST is useful in evaluating trauma patients. It also appears to make emergency department
care faster and better. However, some authorities still have not accepted its use.
. In the right upper quadrant this typically appears in Morison's Pouch
(between the liver
and kidney
). In the left upper quadrant, blood may collect anywhere around the spleen
(perisplenic space). In the pelvis, blood generally pools behind the bladder
(in the rectovesicular space or Pouch of Douglas
). A positive result suggests hemoperitoneum; often CT scan will be performed if the patient is stable or a laparotomy
if unstable. In those with a negative FAST result, a search for extra-abdominal sources of bleeding may still need to be performed.
Medical ultrasonography
Diagnostic sonography is an ultrasound-based diagnostic imaging technique used for visualizing subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions...
examination performed by surgeon
Surgeon
In medicine, a surgeon is a specialist in surgery. Surgery is a broad category of invasive medical treatment that involves the cutting of a body, whether human or animal, for a specific reason such as the removal of diseased tissue or to repair a tear or breakage...
s and emergency physician
Emergency physician
An emergency physician is a physician who works at an emergency department to care for acutely ill patients. The emergency physician is a specialist in advanced cardiac life support , trauma care such as fractures and soft tissue injuries, and management of other life-threatening situations.In...
s as a screening test for blood around the heart (pericardial tamponade) or abdominal organs (hemoperitoneum
Hemoperitoneum
Hemoperitoneum is the presence of blood in the peritoneal cavity. The blood accumulates in the space between the inner lining of the abdominal wall and the internal abdominal organs. Hemoperitoneum is generally classified as a surgical emergency; in most cases, urgent laparotomy is needed to...
) after trauma
Physical trauma
Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
.
The four areas that are examined for free fluid are the perihepatic space (also called Morison's pouch or the hepatorenal recess), perisplenic
Spleen
The spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system. In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells and holds a reserve of blood in case of hemorrhagic shock...
space, pericardium
Pericardium
The pericardium is a double-walled sac that contains the heart and the roots of the great vessels.-Layers:...
, and the pelvis. With this technique it is possible to identify the presence of intraperitoneal or pericardial free fluid. In the context of traumatic injury, this fluid will usually be due to bleeding.
Extended FAST
The extended FAST (eFAST) allows for the examination of both lungs by adding bilateral anterior thoracic sonography to the FAST exam. This allows for the detection of a pneumothoraxPneumothorax
Pneumothorax is a collection of air or gas in the pleural cavity of the chest between the lung and the chest wall. It may occur spontaneously in people without chronic lung conditions as well as in those with lung disease , and many pneumothoraces occur after physical trauma to the chest, blast...
with the absence of normal ‘lung-sliding’ and ‘comet-tail’ artifact (seen on the ultrasound screen). Compared with supine chest radiography, with CT or clinical course as the gold standard, bedside sonography has superior sensitivity
Sensitivity
Stimulus|Sensitivity may refer to:* Sensitivity , the ability to react to a stimulus* Sensitivity , the strength of physical or emotional reaction in people* Sensitivity , variations in process dynamics and control systems...
(49–99 versus 27–75%), similar specificity
Specificity
Specificity may refer to:* Being specific * Specificity , the proportion of negatives in a binary classification test which are correctly identified...
(95–100%), and can be performed in under a minute. Several recent prospective
Prospective
Prospective literally means "looking forward". It can also refer to an event that is likely or expected to happen in the future. For example, a prospective student is someone who is considering attending a school — typically a high school student who is seriously considering applying to a...
studies have validated its use in the setting of trauma resuscitation, and have also shown that ultrasound can provide an accurate estimation of pneumothorax size. Although radiography or CT scanning is generally feasible, immediate bedside detection of a pneumothorax confirms what are often ambiguous physical findings in unstable patients, and guides immediate chest decompression
Chest tube
A chest tube is a flexible plastic tube that is inserted through the side of the chest into the pleural space. It is used to remove air or fluid , or pus from the intrathoracic space...
. In addition, in the patient undergoing positive-pressure ventilation, the detection of an otherwise ‘occult’ pneumothorax prior to CT scanning may hasten treatment and subsequently prevent development of a tension pneumothorax, a deadly complication if not treated immediately, and deterioration in the radiology
Radiology
Radiology is a medical specialty that employs the use of imaging to both diagnose and treat disease visualized within the human body. Radiologists use an array of imaging technologies to diagnose or treat diseases...
suite (in the CT scanner).
Advantages
FAST is less invasive than diagnostic peritoneal lavageDiagnostic peritoneal lavage
Diagnostic peritoneal lavage is a procedure where, after application of local anesthesia, a vertical skin incision is made one third of the distance from the umbilicus to the pubic symphysis. The linea alba is divided and the peritoneum entered after it has been picked up to prevent bowel...
, involves no exposure to radiation and is cheaper compared to computed tomography
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
, but achieves a similar accuracy.
Numerous studies have shown FAST is useful in evaluating trauma patients. It also appears to make emergency department
Emergency department
An emergency department , also known as accident & emergency , emergency room , emergency ward , or casualty department is a medical treatment facility specialising in acute care of patients who present without prior appointment, either by their own means or by ambulance...
care faster and better. However, some authorities still have not accepted its use.
Interpretation
FAST is most useful in trauma patients who are hemodynamically unstable. A positive FAST result is defined as the appearance of a dark ("anechoic") strip in the dependent areas of the peritoneumPeritoneum
The peritoneum is the serous membrane that forms the lining of the abdominal cavity or the coelom — it covers most of the intra-abdominal organs — in amniotes and some invertebrates...
. In the right upper quadrant this typically appears in Morison's Pouch
Morison's pouch
The hepatorenal recess or subhepatic recess is the space that separates the liver from the right kidney. As a potential space, the recess is not filled with fluid under normal conditions. However, fluid can collect in this space in circumstances where the abdomen fills with fluid, such as...
(between the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
and kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
). In the left upper quadrant, blood may collect anywhere around the spleen
Spleen
The spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system. In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells and holds a reserve of blood in case of hemorrhagic shock...
(perisplenic space). In the pelvis, blood generally pools behind the bladder
Bladder
Bladder usually refers to an anatomical hollow organBladder may also refer to:-Biology:* Urinary bladder in humans** Urinary bladder ** Bladder control; see Urinary incontinence** Artificial urinary bladder, in humans...
(in the rectovesicular space or Pouch of Douglas
Pouch of Douglas
The rectouterine pouch is the extension of the peritoneal cavity between the rectum and back wall of the uterus in the female human body....
). A positive result suggests hemoperitoneum; often CT scan will be performed if the patient is stable or a laparotomy
Laparotomy
A laparotomy is a surgical procedure involving a large incision through the abdominal wall to gain access into the abdominal cavity. It is also known as coeliotomy.- Terminology :...
if unstable. In those with a negative FAST result, a search for extra-abdominal sources of bleeding may still need to be performed.
External links
- eMedicine: Blunt abdominal trauma
- FAST exam tutorial
- The FAST examination from Trauma.org, includes tutorial videos.