From the Guidelines
The FAST (Focused Assessment with Sonography for Trauma) scan is a rapid bedside ultrasound examination used to detect free fluid in trauma patients, primarily looking for internal bleeding in the peritoneal and pericardial cavities. This examination is particularly valuable in hemodynamically unstable trauma patients as it can quickly identify the need for surgical intervention without delaying care. The FAST scan consists of four standard views: the pericardial view to check for cardiac tamponade, the right upper quadrant (Morrison's pouch) to examine the hepatorenal space, the left upper quadrant to assess the splenorenal recess, and the suprapubic view to evaluate for free fluid in the pelvis. The extended FAST (eFAST) adds lung views to detect pneumothorax.
Key Components of FAST Scan
- Pericardial view to check for cardiac tamponade
- Right upper quadrant (Morrison's pouch) to examine the hepatorenal space
- Left upper quadrant to assess the splenorenal recess
- Suprapubic view to evaluate for free fluid in the pelvis
- Extended FAST (eFAST) adds lung views to detect pneumothorax
Diagnostic Accuracy of FAST Scan
The sensitivity of FAST scan ranges from 73-88% for detecting intraperitoneal fluid, with specificity around 98-100% 1. However, it's essential to note that FAST cannot reliably detect solid organ injuries without free fluid and may miss bowel or diaphragmatic injuries, so negative results don't exclude significant trauma in all cases. The diagnostic performance of FAST scan remains inferior to the intrahospital FAST, and its feasibility may be impeded by poor conditions, obesity, and low operator experience 1.
Clinical Application of FAST Scan
The FAST scan should be performed within minutes of patient arrival and can be completed in less than 5 minutes by a trained provider. It is a valuable addition to available diagnostic resources in the care of patients with time-sensitive or emergency conditions such as acute thoracic and abdominal trauma 1. The FAST scan can be used to rapidly triage multiple victims in mass casualty situations and can be performed on patients with spinal immobilization and with portable equipment, allowing it to be used in remote or difficult clinical situations 1.
Limitations of FAST Scan
The negative result of a very early performance may not rule out slowly accumulating intra-abdominal free fluid, and a retroperitoneal haematoma can generate intra-abdominal effusion, in particular in the case of patients with complex pelvic injury 1. Therefore, the FAST scan should be used in conjunction with other diagnostic modalities and clinical judgment to ensure accurate diagnosis and management of trauma patients.
From the Research
Definition and Purpose of FAST Scan
- A Focused Assessment with Sonography for Trauma (FAST) scan is a limited ultrasound examination primarily aimed at identifying the presence of free intraperitoneal or pericardial fluid 2.
- The purpose of FAST is to identify free fluid, which necessarily means blood in acute trauma patients, and to help determine the need for further evaluation or operative intervention 2, 3.
Diagnostic Accuracy and Reliability
- The sensitivity, specificity, and accuracy of FAST in detecting free fluid have been reported to be 77.27%, 100%, and 79.16%, respectively, when compared with contrast-enhanced computed tomography (CECT) scans 2.
- The sensitivity and specificity of FAST have also been reported to be 62% and 96%, respectively, in potentially unstable patients as judged by objective hemodynamic parameters 4.
- A negative initial FAST in hemodynamically unstable patients cannot reliably exclude intraabdominal bleeding, and additional diagnostic tests should be performed to exclude intraperitoneal hemorrhage 4.
Clinical Applications and Limitations
- FAST is a useful tool in trauma evaluation to identify intraabdominal fluid early in unstable patients, but its actual value in the diagnostic and treatment pathway of patients with blunt abdominal trauma remains questionable 5.
- The role of FAST in trauma management has evolved over the years, and it is now part of a more comprehensive study of the abdomen, heart, chest, and inferior vena cava 6.
- FAST has limitations, including operator dependence, lack of standardization around education, and variations in practice, quality, and audit 5.