Focused assessment with sonography for trauma (FAST) is now a common diagnostic tool in human and veterinary emergency medicine. Here are three types of veterinary FAST methods that take advantage of the flexibility and accessibility of ultrasound visualization.
1. AFAST
AFAST stands for abdominal focused assessment with sonography for trauma. AFAST is an excellent diagnostic tool to assess veterinary trauma patients. Veterinary professionals and techs can visualize intra-peritoneal blood without invasive or time-consuming tests. Non-radiologists can learn how to perform AFAST to provide immediate assessments in the trauma or acute patient.
Perform AFAST as soon as possible following triage of the patient. You can usually perform AFAST scans while the veterinary patient is being stabilized.
As with all FAST methods, use an ultrasound in B-mode with most probes. Place the animal in the lateral recumbency or right lateral recumbency position. In medically necessary cases, including patients in respiratory distress, scan the veterinary patient while the animal is standing up or in sternal recumbency.
It's not necessary to shave the animal. However, shaving can assist inexperienced ultrasound operators with visualization and interpretation of the ultrasound field.
Scan for AFAST in four places which are as follows:
- Diaphragmatic-hepatic view: caudal to xyphoid process
- Cystocolic view: midline over urinary bladder
- Splenorenal view: over left flank
- Hepatorenal view: over right flank
Scan each of the sites in two planes, ensuring the two planes are oriented at a 90-degree angle to each other. To find blood and other fluid in the ultrasound field, look for black spaces between and adjacent to organs. The black areas are positive for free fluid in the abdomen.
Operators may then rate trauma patients with an abdominal fluid score graded from 0 to 4 depending on the presence of fluid-positive spaces in the ultrasound field. If blood is noted on the AFAST exam, perform serial scans on patients to check for continued fluid accumulation.
AFAST examinations will not always detect signs of penetrating trauma in the abdomen, including puncture wounds and bowel injury. An initial FAST exam may be negative while the patient is actually suffering from an intra-abdominal injury. Always perform full ultrasound scans and other diagnostic tests to check for additional problems in the abdominal areas when patients are stabilized.
2. TFAST
The technique known as TFAST, or thoracic focused assessment with sonography for trauma, continues to evolve as trauma professionals refine the key ultrasound strategies in rapid patient assessment. TFAST basically follows the FAST technique of quickly scanning a specific anatomical region - in this case, the thorax.
Operators scan four places in the thorax region for a rapid assessment of bleeding, punctures, and other issues. The four places scanned in a TFAST examination include:
- Right pericardial views: over the side of the heart
- Left pericardial views: over the side of the heart
- Caudodorsal view: over eighth to ninth intercostal space
- Diaphragmatic-hepatic view: caudal to xyphoid process
In the TFAST exam, look in the diaphragmatic-hepatic view or pericardial view for fluid around the heart that's surrounded by the white line of the pericardium. This is a positive sign for pericardial effusion. For detailed and more advanced TFAST scans, M-mode evaluation offers better visualization of pulmonary conditions in veterinary patients.
Veterinary staff can perform AFAST and TFAST together for more complete assessments of veterinary trauma patients. As with the AFAST exam, the initial thoracic ultrasound assessment of the veterinary patient should be followed up with a complete scan of the thorax.
3. Vet BLUE
Vet BLUE stands for veterinary bedside lung ultrasound. Vet BLUE methodology can be used with trauma, chronic, and acute veterinary patients.
The Vet BLUE technique is a way to easily visualize dry lung versus wet lung using the ultrasound probe. You can see the presence or lack of the Glide Sign (called lung sliding in humans) and A-lines to determine if the lungs are dry or wet.
To perform the Vet BLUE assessment, orient the ultrasound image to show the rib heads at the top middle of the ultrasound field. The rib heads should be viewed as the Gator Sign, where the rib heads become the eyes of the alligator.
Next, find the horizontal white line that would lie over the alligator's nose if it were partially submerged in water. This is the pulmonary-pleural line where the lung should glide over the thoracic wall.
Place the rib head in the middle of the ultrasound field to create the one-eyed Gator, and you should be able to easily visualize the Glide Sign. A-signs without glide indicate pneumothorax, while vertical lung rockets (B-lines) in the inter-costal space view indicate wet lung or edema.
Vet BLUE, AFAST, and TFAST are critical tools in the emergency and acute veterinary setting. As noted above, even non-radiology staff can acquire competent skills using FAST techniques. If your staff is not trained in the technique, invest in FAST training for your emergency veterinary team as soon as possible.
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