Ultrasound in Trauma

Introduction

• POCUS is becoming more ubiquitous in the practice of anesthesiology.
• Ultrasound technology has advanced, making machines more affordable, portable, and accessible.
• POCUS curricula continue to evolve in anesthesiology training programs, increasing physician comfort with performing and interpreting scans.
• Ultrasound is a complement to, not a replacement for, other imaging modalities.
• Ultrasound education is integral to anesthesiology training programs. The training ideally follows a formal certification process, such as that offered by the American Society of Anesthesiologists and should include both image acquisition and diagnostic interpretation.
• Artificial intelligence is rapidly being incorporated into ultrasound machines and can help with specific calculations, such as ejection fraction (EF) or measurement of the inferior vena cava (IVC) diameter, as well as with teaching and guiding image acquisition.

Uses of Ultrasound in Trauma

• POCUS is a relatively low-cost, low-harm, and efficient method for ruling out various pathologies related to trauma.
• Ultrasound machines remain very portable and can be used simultaneously alongside trauma assessments.¹
• POCUS is limited in each user’s expertise in reading various scans and interpreting data; under- or over-calling diagnoses is possible, and thus expertise is required in interpreting scans
• In developing countries or lower-resource settings, access to ultrasound machines may also be a barrier.
• There is a growing body of literature supporting various scan types in a trauma setting (Table 1).

• The focused assessment with sonography in trauma (FAST) has become a staple in the initial management of trauma. It focuses on the quick rule out of abdominal free fluid and pericardial effusion.
• The FAST exam has been expanded to include lung examination in the extended-FAST (E-FAST).
• The E-FAST can assist with ruling out pneumothorax, pleural effusion, or other pleural abnormalities.
• Point-of-care cardiac scans can provide information about wall motion abnormalities, valvular pathology, contractility, and EF of both ventricles, cardiac filling, hemopericardium, or pericardial effusion.
• Large vessel examination can assist in the diagnosis of aortic dissection, IVC filling, and volume status.
• Targeted exams can assist in the diagnosis of secondary injuries such as musculoskeletal injuries, ocular injuries, and genitourinary tract injuries
• Ultrasound can also assist in the placement of critical invasive access, confirmation of the patency of intravenous and intra-arterial access, and endotracheal tube placement
• Ultrasound remains the gold standard for guiding central venous catheter placement.¹
• Gastric ultrasound is useful in the trauma patient who may need urgent surgery, but not immediately. It helps rule out delayed gastric emptying and assess the ability to use a supraglottic airway or to use procedural sedation with a native airway.
• Ultrasound images should be stored under the patient’s medical record number. Ideally, the ultrasound machine should communicate with the hospital electronic medical record (EMR) so that the images are stored centrally and can be easily reviewed
• Departmental quality improvement (QI) metrics should include the use of POCUS imaging as a part of trauma assessments, and images should be routinely reviewed as part of ongoing QI.

FAST and E-FAST Components

• FAST and E-FAST exams are indicated in patients with blunt thoracoabdominal injuries
• Advanced Trauma Life Support has incorporated FAST exams as an adjunct to the primary survey and is recognized as a valuable diagnostic tool
• FAST exams are highly specific for intraabdominal free fluid and pericardial effusion. Meta-analyses indicate that the specificity of such tests is greater than 90%, with sensitivities greater than 70%, and that this increases to over 90% in patients who ultimately require surgery.²
• E-FAST has been shown to be more sensitive and specific than chest X-ray for the diagnosis of pneumothorax and hemothorax.³
• FAST and E-FAST scans are easily reproduced and quick to perform and can be repeated regularly during a patient’s hospital course if their clinical status changes and in various settings (prehospital, emergency department, perioperative setting, intensive care unit).
• Figure 1 provides a useful algorithm for triaging patients based on the results of their FAST exam.

• The FAST and E-FAST exams are commonly done using a curvilinear probe
• There is a total of 4 scanning windows for a FAST exam and a minimum of 6 for the E-FAST exam (Figure 2).

• The first view is the subxiphoid view, which is achieved by placing the probe below the xiphoid process and angling it straight towards the patient’s heart, applying downward pressure
• This view is useful in assessing pericardial effusion, as well as noting the function of the heart and volume status.⁴
• The peritoneal views include the right upper quadrant views of Morrison’s pouch, subdiaphragmatic space, and paracolic gutter; as well as the left upper quadrant which includes the subdiaphragmatic, paracolic and subsplenic spaces⁴
• The bladder view assesses for free pelvic fluid
• A thoracic ultrasound on both sides can assess for pneumothorax, hemothorax, or pleural effusion. For a more in-depth review of lung ultrasound, see the OA summary on lung point-of-care ultrasound (Link) and OA vodcast on Introduction to lung ultrasound (Link)

Focused Cardiac Ultrasound

• Bedside transthoracic echocardiography (TTE) is useful for assessing cardiac function and diagnosing various causes of shock.
• There are 4 main views for bedside TTE: parasternal long axis, parasternal short axis, apical 4- chamber, and subxiphoid 4-chamber views, with the addition of an IVC view also often included after the subxiphoid view (Table 2).
• Focused cardiac POCUS can help differentiate obstructive, cardiogenic, or hypovolemic shock in an unstable patient amidst ongoing resuscitation.

Transesophageal Echocardiography (TEE)

• TEE offers some benefits over TTE for patients who suffered from trauma; it can be performed intraoperatively, while surgery is ongoing when surface echo may not be feasible.⁴
• TEE provides actionable information that can guide resuscitation and monitor for dynamic changes in cardiac function and filling status.
• A focused Trauma Resuscitation Esophageal Echocardiographic (TREE) study has been proposed to guide intraoperative resuscitation in collaboration with the surgeon.⁴

1. RV and LV filling and contractility can guide volume status and resuscitation
2. Evaluate for aortic injury, including dissection
3. Evaluate for tamponade
4. Evaluate for pleural effusion

• TEE allows for a more comprehensive cardiac assessment and can more accurately rule out traumatic aortic injuries than TTE.
• Despite its benefits, TEE is more invasive than surface echocardiography and does pose some risks to patients.
• TEE has multiple contraindications, both relative and absolute; absolute contraindications include unstable cervical spine and esophageal injury, both of which should be ruled out in trauma before proceeding.