ABCDE of prehospital ultrasonography: a narrative review

Abstract

Prehospital point-of-care ultrasound used by nonradiologists in emergency medicine is gaining ground. It is feasible on-scene and during aeromedical transport and allows health-care professionals to detect or rule out potential harmful conditions. Consequently, it impacts decision-making in prioritizing care, selecting the best treatment, and the most suitable transport mode and destination. This increasing relevance of prehospital ultrasonography is due to advancements in ultrasound devices and related technology, and to a growing number of applications. This narrative review aims to present an overview of prehospital ultrasonography literature. The focus is on civilian emergency (trauma and non-trauma) setting. Current and potential future applications are discussed, structured according to the airway, breathing, circulation, disability, and environment/exposure (ABCDE) approach. Aside from diagnostic implementation and specific protocols, procedural guidance, therapeutic ultrasound, and challenges are reviewed.

Keywords: Air ambulances; Diagnostic imaging; Emergency medical services; Emergency medicine; Prehospital; Review; Ultrasonography.

Fig. 1

Normal lung. A normal lung ultrasound image acquired with a 15–6 MHz linear transducer. The ribs are visible with their anechoic shadows on both sides of the image. The pleural line is shown in between the ribs, indicated with two horizontal arrows. Emanating down from the pleural line are comet tails. B-lines (not visible here) also start at the pleural line, but extend all the way down to edge of the image

Fig. 2

Normal lung + B-line. A normal lung ultrasound image acquired with a 5–1 MHz phased-array cardiac transducer. In the middle of the image, one B-line is seen. This is also seen in healthy subjects and a single B-line is without meaning

Fig. 3

Normal lung—M-mode ultrasound image. The ultrasound reflections on the vertical line in the upper part of the image are sequentially displayed from left to right in the lower part as time progresses. It allows to capture the motion of the upper 2D image in the stationary image below. A normal M-mode image of the chest wall and pleura is displayed here. The stationary chest wall produces straight horizontal lines above the pleural line. The lung sliding and movement of the artifacts below produces a grainy image. This is called the seashore sign

Fig. 4

Pneumothorax + A-line. A-lines are reflections of the pleural line caused by gas below the parietal pleura. An A-line is indicated by the arrows. The A is for “air” either within or outside of the lung. In case of a pneumothorax, there are no B-lines (Fig. 2) that may obscure the A-lines making them stand out more clearly

Fig. 5

Pneumothorax—M-mode ultrasound image. There is no visible movement above or below the pleural line. Because all tissue and artifacts are stationary, the M-mode image appears as horizontal straight lines throughout the image. This is called a barcode sign or stratosphere sign

Fig. 6

FALLS protocol. This diagram is an adaptation of the work by Dr. Lichtenstein [39]. Firstly, this diagram shows the type of shock the focus is on. Secondly, the type of ultrasound examination is shown. Thirdly, possible diagnoses to consider are shown including their appearance in terms of the BLUE protocol. Every cause of shock is sequentially excluded for expediting the diagnosis of distributive (septic) shock. FALLS fluid administration limited by lung sonography, BLUE bedside lung ultrasound in emergency, BLUE and the A, B, and A’ profile are explained in Table 1, items 1, 2, and 8, respectively

Fig. 7

Normal hepatorenal recess. A normal ultrasound image of the hepatorenal recess (Morison’s pouch). A phased-array cardiac transducer was used with the abdominal settings. The left arrow indicates the diaphragm. The right arrow indicates the hepatorenal recess. The liver is shown above this line and the right kidney below

Fig. 8

Hemoperitoneum at the splenorenal recess. An ultrasound image of the splenorenal recess (Koller’s pouch). A phased-array cardiac transducer was used with the abdominal settings. The left arrow indicates the diaphragm. The right arrow indicates the splenorenal recess with a hypoechoic collection between the spleen (left) and the left kidney (right). This is the image of free intraperitoneal fluid and is very suggestive for intraperitoneal hemorrhage when encountered in a trauma victim

Fig. 9

Ultrasound transducer positioned at the temporal window. The ultrasound transducer is positioned at the site where the temporal bone is thinnest and the ultrasound beam is least obstructed penetrating the skull (Reproduced with permission from Rob Stoffels and Yvonne Houben)