Clinicians appear to be in favour of the expansion of hand-carried ultrasound, but can European emergency medical service providers afford to implement it?
Philippa Pigache
Hospital Imaging and Radiology Europe reporter
It is logical really. As ultrasound equipment becomes cheaper, smaller and ever easier to use, it has migrated from the laboratory, into other departments of the hospital and beyond.
Radiologists have accepted that it will be used, in a slightly different way, by other medical specialists, and by non-medical staff as well.
Manufacturers started shrinking the ultrasound machines just over ten years ago. Cartbased and hand-carried ultrasound (HCU) made it possible to take sonography to the patient,
rather than wheeling the patient to the machine. Machines the size of a laptop, weighing less than 2.7 kilos, are now commonplace and two years ago even smaller pocket-sized, ‘personal’ devices appeared (see box on pR11). In the emergency department, diagnosis by HCU has shown itself
superior to physical examination in confirming, abdominal aortic aneurysm, ventricular hypertrophy, regional wall motion abnormalities, obstructive uropathy, intrauterine pregnancy and, above all, in the detection of abnormal fluid in body
cavities. It provides secondary support in localising a foreign body, in the assessment of deep vein thrombosis and in musculoskeletal imaging. Transcranial ultrasound is also invaluable in confirming brain death in the absence of a pulse.
And a valuable tool for the emergency physician is clearly also good news for emergency medical services (EMS) in the field.
The first pre-hospital use of ultrasound is claimed by the US military but the first medical report of pre-hospital use, entitled ‘Feasibility of ultrasound in the helicopter’, came from two
French emergency medicine physicians in 1998.[1]
Like most papers on the subject, they found the assumed obstructions to successful scanning in the field and on the move less of an impediment than anticipated. Vibration, avionic electronic interference, cramped space, interference by sunlight or sand, contributed to only a 10% reduction in performance accuracy. In fact, the use of HCU pre-hospital in a wide range of circumstances has a remarkably positive profile in the published literature. Going back seven years, there were reports of problems reading the HCU screen in excessively bright light (on the ground) and in detecting intra-abdominal fluid stripes
(important markers of intraperitoneal bleeding), which were successfully identified with a larger mobile ultrasound machine. At that time, everyone, including the manufacturers, acknowledged that the image quality on hand-held units was
poor compared to larger devices. This is no longer so, it is claimed.
A lack of negative reports may also reflect that use of HCU in the field is still a relatively uncommon occurrence. Equipping emergency medical services with up-to-date imaging equipment, even though costs have recently come down, does not come cheap, and training people to use it successfully is an additional provision and expense.
Who uses prehospital HCU and what for?
Bret Nelson and Kevin Chason, from the Emergency Medicine department of the Mount Sinai Medical School in New York, US, published a very thorough review of emergency medical service
use of ultrasound in 2008.[2] They identify a factor additional to cost that influences prehospital use. In the US, the priority of non-physician emergency crews is to get the patient to a hospital just as fast as possible. However, in other parts of the world – for example, in areas with widely distributed rural populations (Australia), or geographical features that present obstacles to transportation (Norway), the local EMS tend
to invest more time and effort in evaluating and managing the patient at the scene or in transit.
A chapter in Emergency Ultrasound reports on the use of prehospital US in Italy, France and Germany, as well in the USA and Australia.[3] In Italy, EMS began using HCU in 2005. Both ground and air ambulances operating out of Milan carry the devices as an aid to interim patient management as well as evaluation and triage. Dr Felix Walcher, from the department of trauma surgery at Johann Wolfgang Goethe University in Frankfurt, Germany, one of the authors of the chapter in Emergency Ultrasound, works in association with the German air-rescue service (Deutsche Rettungsflugwach – DRF Luftrettung. See figure 2 overleaf). His team undertook a year-long study to compare on-site physical examination and HCU in the diagnosis of suspected abdominal injury using six rescue centres in Germany and the UK. They used the protocol for ruling in a diagnosis (as opposed to the more exhaustive ruling out practised by radiologists in the laboratory) – a
prehospital application of Focused Assessment with Sonography for Trauma (PFAST).
The study confirmed the findings of emergency teams in hospitals: whereas physical examination alone is a poor tool for the identification of bleeding, in the pleural, pericardiac or
peritoneal cavity, PFAST achieved levels of accuracy that compared favourably with ultrasound imaging under optimal conditions in the emergency department. This applied even when the teams carrying out the assessment had received
minimal (one day’s) training in PFAST. ‘Data from the literature suggest that training programmes provide competence in FAST and are associated with a steep learning curve,’ they report.[4]
In the emergency department, it is in the assessment of trauma that HCU has demonstrated the most dramatic diagnostic advantage over physical examination.
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It enables the patient to be transferred swiftly to the part of the hospital where treatment can take place. In the field, where specialist care may be many minutes or even hours away, it becomes even more crucial. Most of the references in Nelson’s comprehensive review report on the use of HCU to carry out
PFAST at the scene or in transit to the hospital. Studies are invariably of HCU diagnostic assessment for specific conditions, partly because FAST or PFAST is ‘focused’ – ie, ruling in a diagnosis, and training in HCU focused assessment is correspondingly specific. Away from the hospital, assessment may be in the hands of medical generalists or paramedics as opposed to experienced emergency physicians, so reliable diagnostic aids become even more important.
Useful in trauma, and also in resuscitation
Studies also confirm the value of prehospital HCU assessment for conditions other than trauma. Nelson reports that in Milan prehospital ultrasound is being evaluated by air and ground teams for three major clinical indications: torso trauma, but also cardiac arrest and acute dyspnoea. It is also employed to assess for pericardial, intraperitoneal and pleural fluid in trauma, to differentiate reversible causes of pulseless electrical activity (PEA), and to differentiate between pulmonary oedema and emphysema.
Potentially treatable causes of cardiac arrest like pericardial tamponade, myocardial insuffiency (coronary or pulmonary artery thrombosis) or decreased blood volume, are examples of
acute, time-dependent critical situations where echocardiography can be an invaluable tool in the field, because, if identified, they can be treated there and then.
Walcher’s colleague, Raoul Breitkreutz, says that none of these diagnoses can be made with standard physical examination or electrocardiography alone, nevertheless most resuscitation
guidelines only recommend pauses in ventilation or chest compressions as ‘brief interruptions’ at a maximum of ten seconds, thereby potentially limiting transthoracic ultrasound examinations.
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He says ultrasound readings can be slotted in prior to, during and after resuscitation to confirm suspected myocardial insufficiency due to acute global, left, or right heart failure, pericardial tamponade, and decreased blood volume. He has developed an algorithm for Focused Echocardiography for Evaluation in Resuscitation (FEER – for other ‘focus’ acronyms, see box on the left) as a protocol that can be applied at point-of-care.[5]
The team tested this protocol with 77 out-ofhospital resuscitation cases which registered neither palpable carotid pulse nor measurable blood pressure or peripheral saturation of oxygen when the emergency team arrived. True PEA was suspected in 30 of these cases, but, in 19, ultrasounddetected
cardiac wall movement – a correctable cause – was treated, and 13 survived to hospital admission. Only one case with no visible cardiac wall movement survived.
There are reports of HCU also being used for the monitoring of pregnant women, when they have been involved in accidents or in emergencies related to their condition, and Nelson details
the use of ultrasound by rescue workers in war or natural disasters under the most unfavourable circumstances on the ground. During the 1999 Turkish earthquake, a study of ultrasound was made as a triage tool. Emergency physicians discovered that the resistive index (a measure of renal vasoconstriction) that can be recorded using Doppler US, increased in patients with acute crush injuries, and correlated with the need for haemodialysis. Training for the prehospital use of HCU Much attention focuses on training people to use US in prehospital situations, not least because EMS teams do not axiomatically include medically- trained operators. Training programmes are invariably condition-specific – trauma, fluid
in body cavities, resuscitation – and evidence is mounting that the length of the training period is less important than its character and content.
Nelson notes that no study had compared variations in the amount of training per provider with the quality of consequent examinations. He says: “Based on current literature, it is difficult to draw conclusions regarding the optimal training criteria for prehospital providers, especially among those not already familiar with the technology.” This is something Walcher and Breitkereutz are trying to do. In their one-day, entry-level courses (FEEL) for trauma and preresuscitation geared to both emergency physicians and paramedics, they include, among other elements, hands-on experience and an important lecture on ‘pitfalls and limitations’. They say that it does not consitute an accreditation in echocardiography but it is a first step towards acquiring competence in focused ultrasound.
The question is what percentage of EMS are actually using HCU? Marketing surveys from IMS, from Frost and Sullivan and, most recently, from Marketstrat predict growth of ultrasound sales to $4.7bn by 2012 driven chiefly by expansion in the HCU sector. Clinicians appear generally in favour of its expansion into prehospital use. However European EMS providers may not be able to afford to implement it.
References
1. Lichetenstein D. Intensive Care Med 24(10):11–19.
2. Nelson BP. Int J Emerg Med 2008;1(4):253–9.
3. Walcher F. Emergency Ultrasound 2008. McGraw-Hill, New York.
4. Walcher F. Brit Jnl of Surg 2006;93:238–42.
5. Breitkreutz R. Crit Care Med 2007;35(5 Suppl):S150–61.
