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KEY POINTS

KEY POINTS

  • Medical diagnostic ultrasound imaging most often uses transducer frequencies between 2.5 and 10 MHz (1 megahertz = 1 million cycles per second).

  • For the focused assessment with sonography for trauma (FAST) examination, either a sector- or convex-shaped transducer (low frequency: 2.5–5.0 MHz) is used to visualize the pericardial space and relatively deep regions in the abdominal cavity (hepatorenal fossa, splenorenal recess, pelvis).

  • A negative FAST examination in the hypotensive patient with blunt trauma, particularly one with a pelvic fracture, should be followed by a second FAST examination in 15 to 30 minutes or a diagnostic peritoneal aspiration.

  • The primary goal in the thoracic component of the extended FAST examination is to detect a pneumothorax or hemothorax in the pleural cavity.

  • The assessment of intravascular volume status during resuscitation can be estimated by measuring the diameter and collapsibility of the inferior vena cava using ultrasound.

  • The ultrasound diagnosis of acute calculous cholecystitis is made by visualizing cholelithiasis, thickening of the wall of the gallbladder, and the presence of pericholecystic fluid.

  • The ultrasound diagnosis of acute appendicitis is made by visualizing an enlarged appendix with an appendicolith, lack of compressibility and diameter under compression of greater than 6 mm, and increased blood flow in the appendiceal wall.

  • A high-frequency linear transducer is used to confirm the presence of a soft tissue infection or abscess and allow for percutaneous drainage.

  • Cardiac goal-directed ultrasound includes the subxiphoid, parasternal long-axis, parasternal short-axis, and apical four-chamber views.

  • During ultrasound-guided catheterization of the internal jugular vein, the transverse view is used to identify puncture of the vessel, whereas the longitudinal view is beneficial to localize the needle tip and wire.

INTRODUCTION

Ultrasound is routinely incorporated into the workup of patients with a variety of trauma, critical care, or emergency surgical disorders.1-6 Despite advances in other imaging modalities such as multidetector-row computed tomography (MDCT), the ability to acquire real-time and repeatable data with ultrasound allows the surgeon to make critical decisions expeditiously and with minimal risk of complications. Surgeons are also capable of obtaining good-quality images and interpreting ultrasound examinations independently.7-9 Given that medical students, surgical residents, and fellows have frequent opportunities to learn the technique of bedside ultrasound examination in patients with trauma and emergency general surgery problems, broad familiarity is typical.10 Similarly, the use of ultrasound in critically ill patients for resuscitation, hemodynamic monitoring, and procedural guidance is now commonly performed.11-18 These critical care ultrasound studies can also be completed at the bedside and, therefore, can avoid transportation of patients out of the intensive care unit (ICU). This chapter reviews the indications, techniques, and currently available data for ultrasound examinations in trauma, emergency general surgery, and critical care patients.

PHYSICS OF ULTRASOUND

Ultrasonography is operator dependent. Therefore, an understanding of select principles of ultrasound physics is necessary so that images may be acquired rapidly and interpreted correctly. ...

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