Upper-airway ultrasound is a quick, non-invasive, and reliable tool to enhance the management of the airway in situations when the anatomy can be altered by trauma (J Intensive Care 2016;4:52). When used during intubation, the endotracheal tube (ETT) can be seen during placement in real time. This can be seen as a vertical artifact at the level of the mucosa-air interface, the appearance of a double-track sign (representing the visualization of the anterior part of the ETT in the esophagus), or the presence of sliding when the ETT touches the anterior wall of the trachea. The ability to confirm in real time the passage of the ETT could be lifesaving in situations where copious amounts of blood or secretions are present or when intubating over a bougie or laryngeal mask airway. Esophageal intubation can also be identified with POCUS; this is seen as the sudden appearance of a “double tracheal sign” and has been shown to be 100% specific for esophageal intubation (J Ultrasound Med 2011;30:671-6) (Figure 1). Airway POCUS can also be helpful during traumatic cardiac arrest where capnography or end-tidal carbon dioxide measurement (ETCO2) may be faulty (Arch Acad Emerg Med 2021;9:e68).
Cricothyroidotomy is a lifesaving procedure in the “cannot intubate, cannot ventilate” situation. Airway POCUS facilitates the identification of anatomical landmarks necessary to perform an emergency cricothyrotomy, improving accuracy in accessing the trachea with an improved first-pass success rate (A&A Pract 2019;13:382-5).
“The FAST protocol now includes the examination of the chest to assess for pneumothorax, now known as E-FAST. More recently, POCUS has moved well beyond the E-FAST, providing potential value for diagnosis and management of trauma patients.”
Gastric POCUS is a recent application applicable in the emergency setting to objectively assess gastric content and the risk of aspiration (BJA Educ 2019;19:219-26). The assessment of gastric content with ultrasound guidance is easy to perform and interpret with a significant impact in decision-making in the perioperative setting. Trauma patients are considered at high risk of aspiration due to delayed gastric emptying and unknown fasting status when unable to provide accurate information. A recent study on anesthesiologists’ clinical judgment on fasting accuracy in urgent surgical patients compared to gastric ultrasound showed a poor to moderate performance of clinical judgement for the diagnosis of full stomach with a misdiagnosis in 55% of cases (Anaesth Crit Care Pain Med 2021;40:100836).
Traditionally, urgent trauma patients were classified as full stomach, requiring rapid-sequence induction (RSI) for intubation and/or general anesthesia. Gastric POCUS showed a change in anesthesia management for 31.1% of trauma patients, supporting its use in the evaluation of fasting status in this population, avoiding the possible adverse effects of RSI and facilitating the use of regional anesthesia techniques (BMC Anesthesiol 2021;21:140).
TEE for trauma
Transesophageal Echocardiography has been traditionally performed by cardiovascular anesthesiologists. Although an examination with transthoracic echocardiography (TTE) is a useful application of POCUS, it also has different limitations within the perioperative and critical care settings. Mechanical ventilation, body habitus, and the sterility of the surgical field can make the use of TTE challenging during the initial resuscitation period. TEE offers better visualization of cardiac anatomy and hemodynamic assessment, improved diagnostic accuracy, and real-time assessment during resuscitation. For critically injured patients with undifferentiated shock despite appropriate resuscitation, TEE can provide valuable real-time information regarding volume status, right and left heart function, and causes of obstructive shock like cardiac tamponade or massive pulmonary embolism. Burns et al. reported TEE abnormalities in almost 66% of acutely injured patients during their resuscitation, many of them with “acceptable” traditional monitoring parameters (A&A Case Rep 2016;6:387-90).
Blunt chest trauma-related injuries to the heart and great vessels might not be easy to diagnose in the unstable patient. Those injuries are usually encountered in patients with a sudden acceleration-deceleration injury mechanism. Contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) might be required to confirm a diagnosis, but in the unstable patient, imaging requiring transportation may be not feasible. The use of TEE has a similar specificity and sensibility in diagnosing blunt traumatic aortic injuries as compared to CT and MRI (J Emerg Med 2020;59:418-23). TEE is also useful to identify different injuries associated with blunt and open chest trauma such as cardiac rupture, papillary muscle avulsion, aortic valve rupture, cardiac contusions, intracardiac shunts, and fragmentation of projectiles.
To date, there are very few TEE protocols described for trauma resuscitation. Teran has described a focused TEE protocol for resuscitation in the emergency department and critical care that includes four basic TEE views (mid-esophageal four chamber, mid-esophageal long axis, bi-caval, and trans-gastric short axis) that are quick and easy to obtain and interpret during resuscitation (Emerg Med Clin North Am 2019;37:409-30). We suggest the use of a similar resuscitation TEE approach adapted to fit the specific needs of the unstable trauma patient, including the basic four views with additional views of the ascending and descending aorta as well as basic doppler applications (Table).