Chapter e299

Applications for US in the ED setting continue to undergo rapid growth, both in the U.S. and internationally. Clinicians who practice in the ED, the critical-care setting, and other acute care settings clearly recognize emergency bedside US’s ability to improve and expedite patient care. Emergent indications for ED US center on detecting and screening for trauma or pneumothorax, cardiac arrest states, abdominal aortic aneurysm (AAA), and ectopic pregnancy, and assistance with vascular access. Urgent indications for ED US include screening for biliary or renal disease and deep venous thrombosis (DVT). US also may assist with the detection and drainage of soft tissue abscesses. Numerous other applications for ED US—including general surgical, testicular, ocular, and procedural guidance—are available, but are beyond the scope of this chapter.

Trauma

The focused assessment with sonography for trauma (FAST) examination is a bedside screening tool to aid clinicians in identifying free intrathoracic or intraperitoneal fluid. The underlying premise behind the use of the FAST examination is that clinically significant injuries will be associated with the presence of free fluid accumulating in dependent areas. The FAST examination was developed as a limited US examination, focusing primarily on the detection of free fluid, and was not designed to universally identify all sonographically detectable pathology. Although a number of groups have subsequently recommended additions or modifications to the standard FAST examination, such as evaluating for pneumothoraces, quantifying the degree of free intraperitoneal fluid present, or following the accumulation of the free fluid, the essence of the examination remains identifying findings that can be interpreted by clinicians in a clinical context.

Ultrasonography offers several advantages over diagnostic peritoneal lavage and CT. Numerous studies have demonstrated that the FAST examination is an accurate screening tool for abdominal trauma.1–9 Advantages of the FAST examination are that it is accurate, rapid, noninvasive, repeatable, portable, and involves no nephrotoxic contrast material or radiation exposure to the patient. There is limited risk for patients who are pregnant, coagulopathic, or have had previous abdominal surgery. The average time to perform a complete FAST examination of the thoracic and abdominal cavities is 2.110 to 4.0 minutes.4 In addition, investigators have demonstrated that a massive hemoperitoneum may be quickly detected with a single view of Morison’s pouch in 82% to 90% of hypotensive patients with an abdominal source of bleeding.8,11 One major advantage of the FAST examination is the ability to also evaluate for free pericardial and pleural fluid. Disadvantages of US include the inability to determine the exact etiology of the free intraperitoneal fluid and the operator-dependent nature of the examination. Other potential disadvantages of the FAST examination are the difficulty in interpreting the images in patients who are obese or have subcutaneous air or excessive bowel gas, and the inability to distinguish intraperitoneal hemorrhage from ascites.12 The FAST examination also cannot evaluate the retroperitoneum as well as CT.

At Level 1 trauma centers, the ...

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