On the heels of advancing technology, the use of medical ultrasound has been moving into more corners of medicine. In less than a dozen cases in the U.S., it’s made its way into the back of ambulances. Most of these services are using ultrasound to diagnose internal bleeding in the presence of traumatic injury, and some are using it to help start difficult IVs. However, ultrasound has much more to offer, and tapping into that resource may mean a major change in how we view our ability to diagnose and treat illness in the field.
Currently, EMS is limited in its ability to take diagnostic images. We can take and transmit 12-lead ECGs, measure capnography and, with such devices as the iStat, take some basic field labs.
However, our lack of ability to actually peer into the human body has always forced us to heavily rely on other assessment approaches and sources of information. Although this lack of visualization has made EMTs and paramedics highly attuned to the subtle clues patients may present, it’s also a major reason the true potential of ultrasound, and ultimately definitive medical diagnosis, may be resisted, or felt to be unnecessary in the field. You can almost hear the words rolling off the lips of a seasoned EMS veteran: “We never had this technology before and got by without it.” Yes, we did, and we used to get by without 12-lead ECGs, capnography, CO oximetry, adult intraosseus (IO) and continuous positive airway pressure (CPAP) as well.
There’s also going to be the traditional hesitation to endorse or adopt ultrasound by our receiving facilities, just as was experienced during the emergence of the prehospital 12-lead some 20 years ago.
When 12-leads were introduced to EMS, nobody really knew what to do with them. We knew they were important, and we knew we could do them, but there weren’t many people who understood why we would want to.
Most people originally thought the big, expensive machines were a waste of money, but the 12-lead eventually became a validated mainstay of EMS, leading to improved cardiac survival with field cath lab activation of incoming ST-segment elevation myocardial infarction.1 It’s often difficult to bring a new practice into our field, but the history of prehospital 12-lead reminds us it’s not impossible.
If a picture is worth a thousand words, an ultrasound could be priceless, especially when you’re running Code 3 down the highway, and that kid you just intubated starts to falter and crash. Was it the rapid sequence intubation drugs? Did the tube come out? Is he bleeding out? Is it a pneumothorax? Does he have something else going on that you missed?
Besides putting your hands on him and trying to listen to his lung sounds over the sirens, there isn’t much you can do but perform CPR and drive Code 3 to the hospital.
Enter ultrasound. You place the small ultrasound probe over the patient’s heart and see that it’s beating but has an unusual appearance; however, you don’t see any signs of tamponade, so you decide to move on.
Next, you decide to check for the sliding lung sign because you know it will help you determine a tension pneumothorax and help confirm your tube placement. You place the probe on the left side of the chest and immediately see the pleura sliding along the chest wall with every breath. This tells you that the tube is in the proper position, but your patient is still very sick.
You then move the probe to the right side of the chest and everything is still. You know immediately that the patient has a right-sided tension pneumothorax, confirmed by ultrasound. With your split-second, accurate diagnosis, you can treat the illness and forgo any needless invasive procedures, and it only took about 60 seconds.
The Reality of Ultrasound
Ultrasound has proven to be clinically useful in one out of six EMS calls.2 In another smaller, ongoing study of ultrasound, its use was found to impact hospital treatment and change care decisions in three of the 11 recorded calls.3 It also confirmed a difficult diagnosis on seven of the 11 calls.
In addition to the impact ultrasound has in zeroing in on clinical conditions, it’s been found to be extremely useful during IV establishment and transcutaneous pacing.
The most common use of ultrasound is the Focused Assessment with Sonography for Trauma, or FAST exam, which is actually a group of exams. It’s sometimes called an E-FAST or extended FAST when an exam for pnuemothorax is added. The FAST exam is designed to allow the user to view areas around the heart, liver, bladder and spleen of a patient to detect free fluid. It’s easy to learn and takes about two minutes to perform when the results are negative; it takes only seconds to perform when findings are positive.
Another common ultrasound study is the Focused Echocardiographic Evaluation in Resuscitation, or FEER exam. This exam is designed to be used during cardiac arrest or severe hypotensive states. It’s been found to be useful in rapidly diagnosing the cause of hypotension, thereby guiding both prehospital and hospital treatment.
The FEER exam has been used during in-hospital management of cardiac arrests to allow physicians to diagnose such conditions as pulmonary embolus, and it has served as an adjunct to the provision of reversal treatment, such as tissue plasminogen activator (tPA).
Sonography has been found to be beneficial in the placement of peripheral IVs. A good linear ultrasound probe can quickly and easily locate large, patent peripheral veins that are otherwise invisible and difficult to palpate. This is helpful for patients in whom IV access is difficult and necessary but IO access is not indicated. Paramedics who are comfortable with this procedure can establish an ultrasound-guided peripheral IV in nearly the same time it takes to start a visually guided IV.
Ultrasound has also proven extremely useful in the placement of central venous catheters and nerve blocks. Ultrasound makes the identification of veins, arteries and nerves, as well as their differentiation from each other and adjacent tissues, quite easy, especially with higher-resolution machines.
The ability to see the location of central vessels improves the safety of central line placement to the point that it may be the deciding factor for services that need to place them but are fearful because of safety concerns.
One of the more interesting “fringe” uses of ultrasound is in the diagnosis of stroke via a component called Transcranial Doppler (TCD). This feature is available only on the high end of the portable ultrasound spectrum and is therefore out of reach for most services. However, Sonosite has recently added the feature as an option to its middle-line S-FAST systems.
The full name of the procedure is Transcranial Duplex Pulsed Wave Doppler. The basic procedure involves placing the probe onto the temporal bone, visualizing the middle cerebral artery (MCA) and taking a flow measurement. This is very effective because 70% of all strokes happen to occur in the MCA.
This procedure is repeated on both the left and right sides, and the two measurements are compared. If the patient shows signs and symptoms of a stroke, and there’s a large discrepancy in the measurements, the findings are considered diagnostic of an ischemic stroke.4
Ischemic and hemorrhagic stroke occur simultaneously so infrequently that it’s difficult to find an accurate statistic of it, so a diagnosis of ischemic stroke essentially rules out a hemorrhagic stroke.5 Only one study has been conducted on the prehospital use of TCD, so more work is needed in this area. But this technology’s potential for EMS is obvious.4
The first EMS service in the world to utilize prehospital ultrasound on a full-time basis was Odessa (Texas) Fire Department.6 In 2000, Odessa paramedics began using ultrasound to diagnose abdominal bleeding and pregnancy.
Since then, Odessa has been joined by many other services in the U.S., including Wise County EMS in Decatur, Texas; Littleton (Colo.) Fire Department; Temple Terrace (Fla.) Fire Department; Oregon Health and Science University Air Medical in Portland, Ore.; Metrohealth Medical Center in Cleveland, Ohio; and Lifelink III in Minneapolis, Minn.
In the U.S., prehospital ultrasound is poorly studied, especially when compared to our European colleagues. This is partly due to the “scoop and run” philosophy adopted by most U.S. EMS systems. Many European countries, such as France and Germany, employ a “stay and play” attitude.7 One reason for this is that many European services dispatch emergency physicians on air ambulances or special ground ambulances, something that is rare in the U.S. because of the lack of direct physician involvement in prehospital medicine. Therefore, prehospital ultrasound is common in both Germany and France.
The ability of non-physician, non-sonographer health-care personnel to perform ultrasounds has been called into question. Yet, all of the studies performed in this area have shown that when the exams were limited to a focused, mechanism-based assessment, as opposed to an organ-based assessment (e.g., cardiac tamponade exam versus examination of the heart), any trained personnel were capable of diagnosing or ruling out the investigated pathologies.
Training & Certification
Ultrasound training can be conducted through a one- or two-day assessment-based course. The courses offered for our personnel include a short didactic session with the majority of the training spent on hands-on practicum. The training frequently uses volunteers as models for student practice; however, some training systems employ actual patients. Cadavers tend to be difficult to obtain and, in the author’s experience, aren’t any more useful than a live model combined with simulation aides, such as the Blue Phantom Ultrasound Training Model.
Ultrasound is a very physical skill; the tactile response and hands-on approach provide more information to the sonographer than just an image. This is one area that makes ultrasound so different from X-ray or computed tomography. If you take a head CT in Dallas, it can be read via Internet by a radiologist in Chicago. All the data you could possibly get out of that CT scan was captured and recorded, and the CT technician doesn’t get anything more than the radiologist.
However, with ultrasound, the sonographer gets the best opportunity to see the patient’s condition due to the real-time images, and they must then take snapshots to show the receiving physician later. That’s why it’s often difficult to read a still sonogram image but easy to perform an actual sonogram.
Because ultrasound offers more data to the examiner than to someone viewing the still images, and because it provides the ability to guide the examination and find points of interest quickly, it’s currently more effective than a CT scan in the field.
It’s important to note that, because of the EMS provider’s physical relationship with the ultrasound image, it’s not possible to become proficient by simply viewing still images or video; instead, it’s generally accepted that proficiency isn’t achieved until around the 25th ultrasound exam.7
An ultrasound technician is registered by the American Registry for Diagnostic Medical Sonography (ARDMS) and is credentialed as a registered diagnostic medical sonographer (RDMS). This same credential is available to emergency physicians who have practiced using ultrasound for more than a year and sit for the difficult ARDMS exam process. However, emergency physicians don’t need to be RDMS-certified to be eligible for insurance reimbursement; they must only be certified by their hospital as ultrasound-capable.7
Paramedics don’t currently enjoy the same credentialing. Insurance doesn’t presently reimburse for paramedic-performed ultrasounds, and there’s no certification process or system for prehospital sonography. Therefore, an ultrasound performed by a paramedic is still a billable event but until insurance rules change, it’s unlikely to be collectable in any significant amount.
As with other new, advanced medical procedures, the equipment selected for use in the field can make the difference between a successful ultrasound program and one that paramedics are unwilling to use and receiving hospital staff views with skepticism. Therefore, if you decide to adopt this technology, you must know what you want to achieve, what studies you want to perform and how much you can spend.
Prehospital ultrasound equipment fits into three categories based on size and shape: handheld, mounted and laptop. The handheld systems are the smallest, most portable systems and the cheapest in almost all cases. However, they tend to offer the lowest number of options and the poorest image quality.
If your only interest is in having crews perform FAST exams, this can be a viable option; however, if you want to perform a more in-depth assessment, desire better image quality, or you’re planning on performing guided IVs, you should consider the other options.
All of the technology in an ultrasound machine is located in the small transducer (probe), the section that projects the ultrasound beam; the rest of the machine is just a fancy television. With the exception of the Sonosite handheld unit, all the current handhelds have single, fixed transducers.
The ability to change the transducer is what allows you to change from one type of exam to another. Therefore, having a fixed transducer limits the device’s ability, but it also limits the cost and eliminates the need to carry an expensive, bulky second transducer.
As with other EMS devices, handheld machines are likely to be carried and potentially dropped. Therefore, ruggedness and the environment in which they’re going to be deployed should be a top consideration. Some units are made of magnesium and built to military specs; others are not.
Mountable systems are a good middle ground. They offer more options, better image quality and changeable transducers. They’re always ready for use without having to be unpacked. Mountable systems cost more than handhelds and are, for the most part, tied to the ambulance and unable to be taken inside a scene. On a positive note, this reduces the likelihood of them being dropped and damaged.
Laptop-based systems are the highest-end systems and provide the most features and best image quality while still offering the portability and ruggedness essential to prehospital medicine. Most importantly, the crisp, sharp lines of the image on these systems make diagnosis of difficult disease processes easier for the provider. That’s why laptop systems are found in most emergency departments (EDs) that carry ultrasound. They provide the ability to use multiple probes and exams. But this extra capability adds an extra level of complexity to their operation. Some less technologically inclined paramedics may be scared away by the number of buttons on a laptop-based system as opposed to some of the simpler mounted and handheld models.
But if you have any interest in performing TCD or some of the other more intricate exams, you’ll have to go with a laptop-based device.
Is Ultrasound Right for You?
A prevailing thought in most of the ultrasound industry is that prehospital ultrasound is beneficial only for rural services and abdominal trauma. The thought process is that if the EMS service is less than 15 minutes from the hospital, crews won’t have time to perform an ultrasound without neglecting patient care.
The same comments were made about IVs, medications, AEDs, pulse oximetry, capnography and CPAP. However, we recently deployed ultrasound on a trial basis at a suburban fire-department-based EMS service with less than a 10-minute Code 3 transport time. Ultrasound was found to be useful and didn‘t impede patient care.
Like many fire-department-based EMS systems, our system responds to all 9-1-1 calls with an engine and an ALS ambulance crew. We’ve found that, by having an experienced team on scene, we’re able to assess and treat our critical patients to the full extent of our protocols without any significant delays in scene time. And, by taking an extra attendant with us on serious or critical cases, we’re better able to perform more in-depth exams, like extra 12-lead ECGs and ultrasounds.
We’ve found that, as the crews’ comfort level increases and more ultrasounds are performed, they begin to implement it into their assessment strategies earlier and more frequently.
We believe that even urban-based systems with short transport times to medical facilities can effectively use ultrasound and make a significant impact on patient care. Detecting a pulmonary embolism in an out-of-hospital cardiac arrest and immediately notifying the receiving facility to have tPA hanging could be lifesaving, and it only takes about 15 seconds.
My colleagues and I are constantly asked, “Why do you need ultrasound in an ambulance?” A simple response would be, “to check for bleeding in the abdomen.” However, this and other factually correct statements about the potential uses of prehospital ultrasound belie the larger picture; ultrasound gives us the capability to perform a more in-depth assessment of our patients with technology proven to be beneficial in the ED. Therefore, like 12-lead ECGs, it’s a logical tool to bring out into the prehospital environment.
EMS has always been known to tread new ground and be willing to deploy a lifesaving technology in areas where it has never been tried before. We’re willing to embrace things from all areas of medicine, regardless of tradition, if it means a potential benefit for our patients. We have a proven track record for success in adopting and adapting technology in the field
Bob Page, AAS, NREMT-P, CCEMT-P, NCEE, wrote recently about paradigms in JEMS. (Read “Teaching Capnography” at jems.com/training.) He described paradigms as “rules or patterns that limit your problem-solving to the boundaries.” That’s one of the greatest assets of EMS: We rarely limit ourselves to boundaries. We consider any and all treatments possible, and we’re willing to do anything for our patients.
EMS is full of constantly evolving paradigm shifts. Therefore, with every piece of new technology, we change what we believe is possible in the back of an ambulance.
The simple act of placing an ultrasound machine in a moving vehicle isn’t going to change the world. But if we develop a systematic, intelligent approach to applying all the benefits of ultrasound to the world of EMS, we’ll change what we believe to be possible in the prehospital setting. We’ll become accustomed to providing treatments and diagnoses to patients we currently consider impossible. Pushing the boundaries is what paramedics have always done; ultrasound is just the next step. JEMS
Acknowledgement: Special thanks to Dave Spear, MD; Roy Yamada, MD; Thilo Hoelscher MD; Keller (Texas) Fire Rescue, Ryan Miller and KFR C-4.
1. Rao, A Et Al. Impact of the prehospital ECG on door-to-balloon Time in ST elevation myocardial infarction. Catheter Cardiovasc Interv. 2010;75:174–178.
2. Hoyer HX, Vogl S, Schiemann U, et al. Prehospital ultrasound in emergency medicine: Incidence, feasibility, indications and diagnoses. Eur J Emerg Med. 2010;epub ahead of print.
3. Bowman JP. Keller Prehospital ultrasound study. Keller Fire Rescue. University of Texas Health Science Center San Antonio.
4. Holscher T, Schlachetzki F, Zimmerman M, et al. Transcranial ultrasound from diagnosis to early stroke Treatment. 1. Feasibility of prehospital cerebrovascular assessment. Cerebrovasc Dis. 2008;26:659–663.
5. Balci K, Utku U, Asil T, et al. Simultaneous onset of hemorrhagic and ischemic strokes. Neurologist. 2007;13:148–149.
7. Ma OJ, Mateer JR, Blaivas M. Emergency Ultrasound. McGraw-Hill Medical: New York, 2008.
8. Quaisar MR. Use of the ‘sliding lung sign’ in emergency bedside ultrasound. Eur J Emergy Med. 2008;15:238–241.
This article originally appeared in September 2010 JEMS as “Visible Improvement: Ultrasound provides diagnostic images in prehospital medicine”
This article originally appeared in September 2010 JEMS as “Visible Improvement: Ultrasound provides diagnostic images in prehospital medicine”
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