Advantages	Disadvantages
• Safe to operator and patient • Rapid • Acceptable in the pregnant patient • Non-invasive • Easily performed/easily learned • Can be performed concurrently with resuscitation • Can be performed in a resuscitation area (i.e. monitored environment) • Repeatable (of particular value in the monitoring of non-operative solid organ injuries) • More cost-effective when compared to DPL or CT • Adult and paediatric applications

Advantages

Disadvantages

• Safe to operator and patient

• Rapid

• Acceptable in the pregnant patient

• Non-invasive

• Easily performed/easily learned

• Can be performed concurrently with resuscitation

• Can be performed in a resuscitation area (i.e. monitored environment)

• Repeatable (of particular value in the monitoring of non-operative solid organ injuries)

• More cost-effective when compared to DPL or CT

• Adult and paediatric applications

• Positive examination requires presence of free intraperitoneal fluid (minimum of 600 mL)

• Cannot determine source of free fluid

• Not reliable for excluding hollow visceral injury

• Not reliable for grading solid organ injuries

• Not reliable for excluding retroperitoneal haemorrhage

• Patient anatomy or pathology may make exam technically difficult (obesity or subcutaneous emphysema)

FAST involves a minimum of four views.

1. The hepatorenal interface (Morison’s pouch) and the right diaphragm. In this view, the transducer is placed at the right midaxillary line between the 11th and 12th ribs. The liver, kidney and diaphragm are viewed. Particular attention is paid to the hepatorenal interface.

2. The splenorenal interface and left diaphragm. In this view, the transducer is placed at the right posteroaxillary line (right side) between the 11th and 12th ribs. The spleen, kidney and diaphragm are viewed. The kidney usually lies more cephalad than on the right.

Table 5.1 Choice of equipment

3. The pouch of Douglas (retrovesical or retrouterine). Ideally the bladder is full. The transducer is placed approximately 1 cm superior to the pubic symphysis. The examination is performed in both transverse and longitudinal planes.

4. Subxiphoid or intercostal views of the pericardium. With a subxiphoid view, the transducer is advanced to the xiphoid process and the beam is directed at the left shoulder. The transducer is variously tilted, swept and rotated to view the pericardial space. An effusion can be suspected when an anechoic area is seen between the liver edge and the right atrium or ventricle. A collapsed right ventricle offers evidence of pericardial tamponade. Clotting blood can be difficult to distinguish from anterior pericardial fat.Other views include the bilateral paracolic gutters.

The applications of FAST are expanding and include penetrating thoracoabdominal trauma and unexplained hypotension in the trauma patient. The use of ultrasound-guided pericardiocentesis offers a safer therapeutic alternative in the presence of pericardial tamponade than traditional ‘blind’ methods.

Abdominal aortic scan

This is an ultrasound scan of the aorta in both transverse and longitudinal planes continuously from the diaphragm to the aortic bifurcation. The study includes measurement of the maximum aortic diameter in both planes.

If an aneurysm is present several additional items need to be assessed, including:

• proximal edge, especially relationship of aneurysm to origin of renal arteries

• distal extent, especially relationship to origin of common iliac arteries

• presence of thrombus

• presence of dissection

• true aneurysmal diameter (outside to outside edge)

• residual lumen diameter

• presence of haematoma surrounding aorta in rupture

• presence of free intraperitoneal fluid.

The presence of an abdominal aortic aneurysm (AAA) on ultrasound in the unstable patient confirms the need for laparotomy.

Indications for ultrasound to detect AAA include presence of syncope, shock, hypotension, abdominal pain, abdominal mass, and flank pain or back pain, especially in the older patient.

OTHER APPLICATIONS

• Pregnancy:

• First trimester pelvic ultrasound to establish the location of the pregnancy and fetal heart rate in the symptomatic pregnant patient or the asymptomatic patient with risk factors for ectopic pregnancy.

• Second and third trimester pelvic ultrasound for detection of fetal cardiac movement, location of placenta and the evaluation of the pregnant trauma patient.

• Echocardiography can be used to assess for pericardial effusion/tamponade, the presence of cardiac mechanical activity in cardiac arrest and pulmonary embolus. Rapid identification of these pathologies may lead to potentially life-saving interventions.

• Biliary ultrasound—cholecystitis and cholelithiasis are best imaged with ultrasound.

• Renal ultrasound—ultrasound images the kidneys well and can be a sensitive bedside test for hydronephrosis.

• Assessment of above-calf deep venous thrombosis.

• Procedural uses (see Table 5.3). This includes use for vascular access, drainage of pleural effusions and performance of lumbar puncture. Ultrasound may localise the percutaneous insertion/incision site before the procedure or may provide real-time guidance of the procedure with needle, catheter or other device.

• Localisation of foreign bodies.

Table 5.3 Procedural applications for emergency department ultrasound

Application	Strengths and uses	Limitations
	Body habitus Anticoagulation Lack of anatomic or palpable landmarks

Vessels may be difficult to visualise without Doppler technology Bladder size and aspiration

Avoids dry taps

Avoids urethral–catheterisation

Abscess location and aspiration Soft tissue infection without clear fluctuance Other sonolucent structures Thoracocentesis and paracentesis Localisation of fluid and avoidance of viscera Pericardiocentesis Foreign body localisation Excellent visualisation in fluid and uniform surrounding tissue Lumbar puncture Arthrocentesis