FAST Exam

See Also

Subcostal Echocardiogram View (Subxiphoid Echocardiogram View)
Right Intercostal Oblique Ultrasound View
Right Coronal Ultrasound View
Left Intercostal Oblique Ultrasound View
Left Coronal Ultrasound View
Suprapubic Ultrasound View (Long Axis or Longitudinal View)
Lung Ultrasound for Pneumothorax (Sliding Lung Sign, Lung Point)
Emergency Echocardiography
Ultrasound

Background

FAST Exam typically takes 2-4 minutes depending on level of experience
1. May take as little as 10 seconds for each of the 7 views
FAST Exam is an integral part of the Trauma Primary Survey
1. In some centers, FAST Exam is performed in place of auscultation of lungs and heart as part of the Primary Survey
Chest evaluation is the highest yield portion of the FAST Exam
1. Chest findings are immediately actionable without further testing (although CT Chest may be performed)
  1. Pleural Effusion Test Sensitivity approaches 100%
  2. Pericardial Effusion and Cardiac Tamponade Test Sensitivity approaches 100%
  3. Pneumothorax evaluation Test Sensitivity approaches 100%
2. Contrast with identification of abdominal free fluid for which Test Sensitivity varies from 22-85%
  1. FAST Exam will miss early or slow intraabdominal Hemorrhage
  2. Often requires CT Abdomen for definitive diagnosis

Precautions

Repeat serial FAST Ultrasound exams
1. Initial scan often misses important findings (typically due to haste of completing full survey)
Pleural Effusion and Hemothorax (right and left intercostal views)
1. Air in lung normally obscures lung and diaphragm appearance
2. Pleural Effusion and Hemothorax by contrast appear black, anechoic and enhance the lung boundary
Abdominal FAST Exam is most helpful when positive (see efficacy below)
1. FAST Exam is at best, a "rule-in" test to direct emergent surgical management in acute significant Trauma
  1. Identifies large volumes of intraabdominal blood
  2. Morrison's Pouch (right coronal) is most useful view and most likely site to identify intraabdominal blood
    1. Test Sensitivity increases when performed with patient in Trendelenburg position (may replace left coronal and suprapubic views)
    2. If positive in Trendelenburg position, but negative when supine, may quantify as smaller volume of blood
2. FAST Exam should NOT be used as a "rule-out" test (esp. Abdominal Trauma) to replace definitive imaging
  1. A negative FAST Exam does not have adequate Test Sensitivity (especially in blunt Trauma) to reassure
  2. A negative FAST Exam should not dissuade CT Abdomen or exploratory surgery in Abdominal Trauma
Complelety visualize common areas of missed fluid pockets
1. Right Coronal Ultrasound View
  1. Lower tip of the liver (follow morrison's pouch medially and inferiorly)
2. Suprapubic Ultrasound View
  1. Fluid pocket is superior (screen left) and deep to Bladder in long axis (probe indicator 12:00)
3. Left Coronal Ultrasound View
  1. Fluid will collect superficial to Spleen (instead of between Kidney and Spleen)
Modifications for children
1. RUQ (Morrison's Pouch) and LUQ (Splenorenal) views are anterior in children (compared with adults)
  1. Position probe at mid-axillary line for RUQ and LUQ in children

Efficacy

FAST Exam is operator dependent for identifying free fluid
1. Only 10% of fast users detect <400 cc free fluid on FAST Exam
  1. Branney (1995) J Trauma 39(2): 375-80 +PMID:7674411 [PubMed]
2. Skilled ultrasonagraphers can detect down to 100 cc free fluid (200 cc on average)
  1. Von Kuenssberg (2003) Am J Emerg Med 21(6):476-8 [PubMed]
Free fluid in Penetrating Trauma
1. Test Sensitivity varies from 50-80%
Free Fluid in Blunt Abdominal Trauma
1. Stable Patient Test Sensitivity: 22%
2. Unstable Patient Test Sensitivity: 28%
3. Test Sensitivity when CT showed free fluid: 35%
4. Carter (2014) Injury 46(5):817-21 +PMID:25498329 [PubMed]

Preparation
Ultrasound

Transducer selection
1. Low frequency probe (deeper penetration): 3-5 MHz Curved Linear Probe
Transducer indicator positioning is based on the patient's body as a clock face
1. Head: 12:00
2. Left hand: 3:00
3. Feet: 6:00
4. Right hand: 9:00
Transducer orientation
1. Use long access (12:00) positioning for most views of Abdomen and chest
  1. Exception: Subcostal or subxiphoid view
  2. Rotation of probe along rib margins to reduce rib shadowing is typically needed
2. Rotating probe slightly into oblique orientation may decrease rib shadowing
Patient position
1. Abdominal views are best obtained with patient flat (supine) or in trendeleburg position