William G. Heegaard, M.D., MPH, Rob Reardon, M.D. and Scott Joing, M.D.
The rapid growth of helicopter emergency
medical services (HEMS) transport both in the United States and in
Europe has mandated that we seek better ways to improve transport care
in critically ill patients. Currently in the US, we have a minimum
of 300,000 helicopter and 150,000 fixed wing transports per year. (1)
Emergency Department ultrasound has been shown to reduce morbidity and mortality in critically ill patients. (2,3) The next logical step was to apply this diagnostic tool to the pre-hospital setting. Recent advances in ultrasound technology have made high quality and handheld ultrasonography available to two pre-hospital emergency care areas: helicopter emergency medical services (HEMS) and ground ambulances. HEMS is a logical area for the investigation of pre-hospital ultrasound given the critical and time-sensitive nature of its transported patients. Most of the published data in the field of HEMS is based on case reports or observational studies. Several small studies evaluating HEMS both in the United States and Europe have been reported. (4-7)
Price and colleagues (4) showed in 2000 that Focused Abdominal Sonography for Trauma (FAST) exams could be performed in helicopters with relative ease and speed (mean exam time 3 minutes). Their study included 14 patients, 10 of whom were simulations. Melanson et al. (5) found that after a 3 hour training period in the FAST exam, performance was not proficient in over 48% of trauma patients. The causes for this were thought to be of a logistical and technical nature. In 2004, Heegaard et al. (6) used a focused template for didactic ultrasound training with additional hands-on training in an emergency department (Table 1). He found that flight clinicians could perform a wide variety of ultrasound views with good long term retention over a year. Ultrasound exams were performed proficiently in the helicopter, although time and space constraints limited the clinicians' ability to perform the full FAST exam. Polk et al. (7) described in 2004 how ultrasound could be utilized to perform a screening exam (the FETUS exam) when transporting obstetrical patients by helicopter. This is a significant contribution because monitoring the fetus in the helicopter using traditional methods of Doppler auscultation is difficult and not reliable.
Figure 1a and Figure 1b: Helicopter emergency medical services (HEMS) using ultrasound.
Very little work has been published in the area of ultrasound use in ambulance transports. Several European ambulance services are currently using ultrasound routinely during patient transportation (personal communication). A German group (8) reported that ultrasound altered pre-hospital and hospital patient management in 37% of cases. They also found a 97.5% specificity and 100% sensitivity for their FAST exams in the field. Other research groups including in the United States are currently working on large prospective trials evaluating the utility of ultrasound during ambulance and helicopter transport.
Potential applications of HEMS and ground ambulance US include but are not limited to:
- FAST exam to detect free intra-abdominal fluid on trauma patients to expedite definitive care.
- Use of a focused cardiac ultrasound exam in hypotensive patients to place them in one of four shock states: Severe hypovolemia, cardiogenic shock, pericardial tamponade or right ventricular obstruction.
- Fetal monitoring and evaluation in obstetric patients.
- Early detection of pneumothoraces.
- Early evaluation of cardiac arrest and potential detection of PEA.
- Ultrasound technology
allows for high quality ultrasound imaging to occur in the pre-hospital settings.
- The use of ultrasound in
the pre-hospital setting has the potential to improve trauma, cardiac
and obstetric care.
small research projects on HEMS ultrasound and ground EMS ultrasound are ongoing in the
USA and Europe.
- Larger multicenter
pre-hospital ultrasound studies are needed.
Abdominal and Aorta
Pelvic and obstetrical
Table 1: Template for didactic teaching of US for air medical clinicians.
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