USS in Trauma

Abdominal

FAST
Most use in unstable pts
- especially non-responders who need urgent identification of bleeding sources.
Hepatorenal space most sensitive (80% sensitive in pts in shock)
- next is LUQ splenorenal view (60%)
- then pelvis (40%)
- may be enhanced by repeating after an interval and having pt in Trendelenburg if tolerated.
Limited by patient habitus, subcut emphysema, low sensitivity for retroperitoneal injuries.

What if +ve?
Stable? --> CT
Unstable? --> OR

Technique
Rapid sequential view of abdo.
1. Pericardial sac;
- subxiphoid directed to L shoulder
- optimize US gain settings (intracardiac blood should be anechoic)
2. RUQ; Morrison's pouch
- look for anechoic density.
- over R inferior ribs angle probe between ribs to obtain view
- probe in posterior axillary line
3. LUQ: splenorenal fossa
- over L lower ribs, best if patient can breathe deep and hold.
- place just behind posterior axillary line
4. Bladder: pouch of douglas
- transverse and longitudinal plane
- evaluates for pelvic bleeding.
- more accurate if there is a full bladder.

Negative fast should be followed by a more definitive test if stable ie. CT

Other Abdo US in Trauma
Can show free air; loss of peritoneal sliding
Trajectory of penetrating wounds; direction and depth.

Thoracic

Pleural Spaces
Lungs essentially impervious to USS due to high acoustic density of air.
But good for pleural space, where trouble often lies.

Pleural sliding

Normal lung movements create sliding
Demonstration useful to exclude pneumothorax.
May be superior to AXR, where small pneumothoraces can be missed (but; clinical value of this?)
If absent: non-specific
- apnoea, pneumothorax, pleural fusion, death
--> move medially until sliding shown; confirms pneumo and also shows its extent.

Comet-tail artifacts
Lung field pathology radiating into lung field
Show fluid in lung, e.g. pulmonary contusion
Requires experience to detect.

Technique
Begin mid-clavicular line, 4-5th rib spae.
Visualize and confirm hyerechoic pleural interface and assess lung sliding
Repeat in contralateral chest.

"Extended FAST"
For detecting haemothorax
Place in mid-axillary line over lower ribs
Demonstrate liver and spleen relation to overlying diaphragm (a bright hyperechoic line)
Dependent fluid collections appear dark.

Cardiac
Not a part of routine FAST, but useful in the right hands
Can show tamponade
Dilated vs empty heart, flat vena cava, or gross contractility.
Can estimate Ventricular Function with experience.
Can distinguish PEA from pseudo-PEA (weak contractions; aortic pressure recordable; barely elsewhere).