1. Correct Answer: C. Hepatorenal, splenorenal, suprapubic, subxiphoid

Rationale: The FAST examination is indicated in patients who are hemodynamically unstable following blunt trauma. The examination allows for rapid assessment for hemoperitoneum and hemopericardium as the cause of hypotension. In addition, solid organ injury may be identified, but the sensitivity is inadequate to exclude these injuries on the basis of ultrasound alone. The FAST examination includes views of the pericardium from the subxiphoid window and the abdomen from the right upper quadrant (hepatorenal), left upper quadrant (splenorenal), and suprapubic (pelvic) windows. Views of the left and right chest are obtained in the eFAST examination to evaluate for pneumothorax and hemothorax. Additional views can be pursued for additional information (e.g., parasternal), but are not part of the traditional FAST examination.

1. Rozyck GS, Oschner MG, Schmidt JA, et al. A prospective study of surgeon performed ultrasound as the primary adjuvant modality for the injured patient assessment. J Trauma. 1995;39(3):492-498.

2. Correct Answer: B. 200 mL

Rationale: It takes approximately 200 mL of free fluid to be reliably detected on ultrasound. A volume smaller than this may be occasionally visible, but is unlikely to be the cause of hemodynamic instability. That said, one should repeat the FAST examination if ongoing bleeding is suspected, as an initial examination may be negative because of a small fluid volume. Also, a positive FAST does not necessarily mean that a patient needs an intervention, since many injuries can be managed nonoperatively.

1. Branney SW, Wolfe RE, Moore EE, et al. Quantitative sensitivity of ultrasound in detecting free intraperitoneal fluid. J Trauma. 1995;39:375-380.

3. Correct Answer: A. Second-third intercostal space, midclavicular line

Rationale: Pneumothoraces tend to be “antidependent,” because the lung tissue is heavier than the pleural airspace. Therefore, evaluation for pneumothorax generally starts anteriorly and apically, at approximately the second or third intercostal space, in the midclavicular line, where a small pneumothorax is most likely to be detected. However, localized pleural disease is possible, so a more thorough examination of the chest is warranted if clinical suspicion is high.

1. Kirkpatrick AW, Sirois M, Laupland K, et al. Hand-held thoracic sonography for detecting post-traumatic pneumothoraces: the extended focused assessment with sonography for trauma (EFAST). J Trauma Inj Infect Crit Care. 2004;57(2):288-295.

4. Correct Answer: D. 86% to 100%

Rationale: The eFAST is composed of the traditional FAST examination with added views of the chest to identify and diagnose pneumothorax and hemothorax. The sensitivity for pneumothorax with this examination approaches 86% to 100%, in contrast with chest x-ray, which has a sensitivity 30% to 80%.

1. Schellenberg M, Inaba K, Bardes JM, et al. The combined utility of extended focused assessment with sonography for trauma and chest x-ray in blunt thoracic trauma. J Trauma Acute Care Surg. 2018;85(1):113-117.

5. Correct Answer: D. >90%

Rationale: Ultrasound is an excellent tool for detecting hemothorax in the trauma patient with blunt and penetrating chest injury. Multiple studies have assessed the utility of ultrasound to detect clinically significant hemothorax and they have shown 100% sensitivity and specificity with no false-negative or false-positive findings.

1. Governatori NJ, Saul T, Siadecki SD, Lewis RE. Ultrasound in the evaluation of penetrating thoraco-abdominal trauma: a review of the literature. Med Ultrason. 2015;17(4):528-534.

6. Correct Answer: C. 60% to 70%

Rationale: An eFAST examination can be used to detect intra-abdominal injury in the blunt and penetrating trauma patient, but the sensitivity for solid organ injury and small-volume hemoperitoneum is significantly less than that for CT scan. With a small volume of fluid (<200 mL), the sensitivity is 60% to 70%, which has been shown over multiple trials. Fortunately, the sensitivity increases with increasing blood volume and is excellent when a hemodynamically significant amount of blood is present in the peritoneum. For this reason, serial reassessment is important if ongoing bleeding is suspected.

The moderate sensitivity may argue against performing eFAST in a hemodynamically stable patient. But, it is important to note that even though the sensitivity is low, the specificity of a positive eFAST is quite high (>90%) in most studies. Hence, a positive eFAST after an abdominal trauma identifies at-risk patients, though it cannot rule out solid organ injury.

1. Branney SW, Wolfe RE, Moore EE, et al. Quantitative sensitivity of ultrasound in detecting free intraperitoneal fluid. J Trauma Inj Infect Crit Care. 1995;39(2):375-380.

2. Dolich MO, McKenney MG, Varela JE, et al. 2,576 Ultrasounds for blunt abdominal trauma. J Trauma Inj Infect Crit Care. 2001; 50(1):108-112.

3. Natarajan B, Gupta PK, Cemaj S, Sorensen M, Hatzoudis GI, Forse RA. FAST scan: is it worth doing in hemodynamically stable blunt trauma patients? Surgery. 2010;148(4):695-701.

7. Correct Answer: B. A 45-year-old woman with BP 85/50 mm Hg after an MVC

Rationale: The FAST and eFAST examinations are noninvasive tests that can be performed concomitantly with resuscitation. The use of ultrasound evaluation is most indicated in a blunt trauma patient who is not stable to transport to CT, to evaluate for intraperitoneal fluid and determine the need for immediate operative intervention. CT is the preferred method of imaging for a stable patient and may provide information about other organ injuries as well. Penetrating trauma patients would be expected to have some degree of fluid in the chest or abdomen (depending on the site of injury), and a negative eFAST examination would not provide adequate reassurance; thus, it would not help clinical decision-making.

1. EAST Practice Management Guidelines Work Group. J Trauma. 2002;53(3):602-615.

8. Correct Answer: A. 2 to 5 MHz curvilinear probe

Rationale: Ultrasound probes penetrate tissue levels according to the frequency (MHz) of the transducer. Higher frequency probes have less penetration, but greater resolution at shallow depths. Lower frequency probes have greater penetration and allow for visualization of deeper structures. The 2 to 5 MHz curvilinear or convex array probe is best used to evaluate deep abdominal structures for injury. The 1 to 5 MHz phased array probe has a smaller footprint and allows for more advanced manipulation of the ultrasound beam, which is best used for pediatric examinations and echocardiography, although it would be a reasonable alternative if the curvilinear array probe was unavailable. The 5 to 12 MHz linear transducer probe is best used for superficial structures and vascular access, as well as evaluation of pneumothorax. The 8 to 13 MHz intracavitary probe is best used for transvaginal and oral evaluations due to its high-resolution images and the shape, which allows it to image from within a body cavity.

1. Enriquez JL, Wu TS. An introduction to ultrasound equipment and knobology. Crit Care Clin. 2014;30(1):25-45.

9. Correct Answer: B. Figure 60.2B

Rationale: In addition to lung sliding seen on real-time B-mode ultrasound, M-mode can be used to detect motion. In normal lung ultrasound, a “seashore sign” is seen, indicating motion of the pleural layers below the chest wall, as seen in Figure 60.2D. The “barcode” or “stratosphere” sign indicates no motion of the pleura or lung, as seen in Figure 60.2B, and is indicative of pneumothorax. B-lines are seen with pulmonary interstitial fluid (Figure 60.2A), and their presence excludes pneumothorax at that location. A dark stripe around the lung can be seen with a pleural effusion or hemothorax (Figure 60.2C).

1. Lichtenstein DA. Lung ultrasound in the critically ill. Ann Intensive Care. 2014;4(1). doi:10.1186/2110-5820-4-1.

10. Correct Answer: C. The eFAST examination has little diagnostic value for hemoperitoneum in this setting

Rationale: The eFAST will detect intra-abdominal or intrathoracic fluid, but is unable to reliably differentiate between types of fluid. Although a hematocrit level may be apparent after blood cells have settled, in the acute setting, blood cannot be reliably differentiated from other fluids. Because of this, the abdominal and posterior thoracic views of the examination may be confounding, and additional clinical information may be necessary to guide management.

1. Maitra S, Jarman R, Halford N, Richards S. When FAST is a FAFF: is FAST scanning useful in non-trauma patients? Ultrasound. 2008;16(3):165-168.