Integrating ultrasound in emergency prehospital settings

MANSOOR KHAN, SARAH MURTHI, HEIDI LEE FRANKEL and THOMAS M. SCALEA

As previous and future chapters will attest, ultrasonography (US) is an indispensable modality in assessing patients in the hospital and outpatient setting. In the past few years, compact, robust, and portable US machines have been developed for use in various prehospital settings. Recent technologic advances have led to the development of battery-powered, light, handheld portable devices. In addition, ease of use, simplification of technology, and facilitated connectivity allow allied providers to perform US in a variety of austere settings.

Unlike computerized tomography (CT) and magnetic resonance imaging (MRI), US represents a more mobile diagnostic tool. However, unlike the aforementioned modalities, US operation requires the operator, or the person guiding the operator, to have an intimate knowledge of the anatomy of the region they are scanning and the ability to interpret pathology on the US image. Nonetheless, if a focused question is asked or if the images can be shared via telemedicine while the operator is proctored through the examination, US can be of great value in the austere setting of disaster medicine.

There are now several pocket US scanners weighing substantially less than 2 pounds. The GE V SCAN Portable Ultrasound weighs less than 1 pound and is about the size of a smartphone and can be used for torso imaging. The Acuson P10 (Siemens Medical Solutions, Malvern, PA) is also pocket sized and is used for similar applications. The SonoSite 180 (SonoSite, Bothell, WA) is slightly larger, but can be used for both vascular and torso imaging. Additional portable technology is on the horizon.

A prospective evaluation in a hospital environment, determined that handheld focused assessment sonography in trauma (HHFAST) examination was equivalent to the FAST examination, using more conventional equipment. HHFAST had a sensitivity of 78%, specificity of 100%, positive predictive value (PPV) of 100%, and negative predictive value (NPV) of 97%.¹^,² HHFAST can detect intraperitoneal fluid with high degrees of accuracy. It will miss some injuries, but the majority of injuries missed do not require therapy.³ In addition, field US, using the HHFAST, can also be performed by nonphysician providers. With close supervision, paramedics can adequately obtain and interpret FAST and abdominal aortic US images under protocol.⁴

Remote location imaging

Popov et al ⁵ set out to demonstrate both the simplicity and robustness of existing US technologies in a remote location. They evaluated telementored resuscitative extended FAST (e-FAST) US examination. An expert interpreter guided a first responder located midmountain at a commercial ski resort. The test subject was a healthy volunteer. US images were obtained on a first-generation SonoSite 180 machine and were converted to digital video using a readily available video converter. A head-mounted camera provided a macroscopic view of the examination, allowing the remote examiner to view both the patient and examiner’s hands, while simultaneously viewing the US results (Figures 48-1 and 48-2).^6–8

Figure 48-1 Remote imaging on a mountainside. (Image courtesy Dr. Paul McBeth.)

Figure 48-2 EFAST on a mountainside. (Image courtesy Dr. Paul McBeth.)

Remote US has also been evaluated and tested aboard Aquarius, an underwater habitat off the Florida Keys, as part of the NASA Extreme Environment Mission Operations (NEEMO). The life sciences mission NEEMO 7 investigated the role of US examination of the abdominal organs and structures. US-trained and untrained aquanaut crew members conducted a series of diagnostic and interventional procedures with remote guidance from experts more than 3000 km away. Researchers demonstrated that mean efficiencies were slightly higher with telementoring than with the use of a procedure manual.⁹

Disaster and prehospital medicine

The role of US in disaster medicine has not been well established and is generally limited to case reports and case series. A report by the Disaster Medical Assistance Team (DMAT), responding to the aftermath of a cyclone in Western Australia, demonstrated that US-competent physicians were able to use portable US on casualties to exclude intraabdominal hemorrhage, pericardial fluid, pneumothoraces, and hemothoraces. The US machine had a weight of 3.7 kg (MicroMaxx, SonoSite, Bothell, WA). It was powered by using a self-contained, rechargeable battery. A 60-mm, 5-2-MHz curvilinear probe and a 38-mm, 10-5-MHz linear probe were selected as most appropriate for the likely requirements. Information obtained using US made initial patient management and subsequent decisions regarding triage for transport safer and based on more detailed clinical information.¹⁰^,¹¹

Sarkisian et al ¹² reported from the Armenian earthquake of 1988, in which US was performed as a primary screening procedure in 400 of 750 mass casualty patients with trauma who were admitted to a large hospital within the first 72 hours after the earthquake. Two real-time sector scanners were used in the reception area of the hospital, and the average time spent on one patient was 4 minutes. More than 130 follow-up ultrasonographic examinations were required. Impressively, trauma-associated pathology of the abdomen and retroperitoneal space was detected in 12.8% of the patients, with 1% false negatives and no false positives.

In the Marmara earthquake, which occurred on August 17, 1999, 639 people had renal complications and 477 needed hemodialysis treatment because of acute renal failure caused by crush injury. This led Keven et al ¹³

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