A deep dive into the use of point-of-care sonography in the field
You’re working on an ALS unit dispatched to an unconscious patient who is now in cardiac arrest. First responders work in concert to administer high-performance CPR.
As you enter the home and lay eyes on your patient, a colleague gives you a brief report and concludes that the automated external defibrillator (AED) advised not to deliver a shock.
You and your partner quickly ensure that effective CPR is underway. You gain vascular access and push epinephrine and, without compression interruption, establish an advanced airway. Your end-tidal carbon dioxide is calibrating and, during the next rhythm check, you quickly ascertain that the patient still lacks a palpable pulse.
High-performance CPR is continued as you transition the patient to your monitor.
At first glance, you see what appears to be an organized narrow complex rhythm at a rate of 95 beats per minute, although your patient still lacks a palpable pulse.
As your own heart rate begins to rise, you deftly wipe away the sweat from your brow and contemplate the next intervention.
How do you organize the limited physiologic and historic data you’ve acquired over the last few minutes? You decide to refine your protocol to follow the ACLS algorithm for pulseless electrical activity (PEA).
After intubating, you notice the left chest wall isn’t rising. Is this evidence of a tension pneumothorax from positive pressure ventilation, or could it be a right main-stem intubation? Should you needle decompress?
Ultrasound in the Resuscitation Toolkit
Sonar technology was invented in the early 20th century to guide ships through turbulent waters and to help avoid hitting icebergs.
Today, the technology has evolved into a highly effective, portable and relatively durable means of gaining otherwise “invisible” information at the patient’s side. In 2004, the American Institute of Ultrasound Medicine (AIUM) held a conference on compact ultrasonography and concluded that an “ultrasound stethoscope is rapidly moving from theoretical to reality.”1
Once the exclusive domain of radiology, cardiology and obstetrics, emergency physicians have brought ulrasound technology to the bedside of their sickest patients to help answer critical questions that might otherwise take hours to decipher.2 In the hands of a trained provider, ultrasound allows one to see inside the patient and use that data to guide resuscitation.
The speed at which point-of-care ultrasound (POCUS) technology has become a standard in the ED suggests its potential to improve patient outcomes in the prehospital arena. Whether or not this efficiently translates to our prehospital environment can’t be assumed, and must be explored further.
Although there are many innovations in prehospital care, three overarching categories remain paramount and warrant attention: 1) practice improvements and infrastructure upgrades that facilitate patient care; 2) programs that reduce harm and risk for the provider, thus creating a safer practice environment; and 3) tools, tactics and strategies which ultimately combine to result in improved patient outcomes.
Some would argue that more technology would solve problems in the EMS sphere. These same individuals would argue that technology is the panacea to prehospital problems.
A controversial, yet relevant example is mechanical CPR. Adoption of this new technology is supported by prospective EMS research indicating tremendous variability in the quality of manual CPR (rate, depth and adequacy of recoil during compressions).3
Further post-hoc analysis of data gathered by the Resuscitation Outcomes Consortium demonstrates that only 45% of cases, using available data meeting a predefined definition, show “acceptable quality CPR.”4
However, some are quick to dismiss mechanical CPR, citing research that current use fails to show patient outcome improvement when studied prospectively and compared to high-performance CPR.5
Let’s put technology aside for a moment. The most valuable resuscitation tool in the ambulance isn’t technology, but rather the medical decision-making ability of the prehospital providers.
Before attempting to integrate advanced technology (proven or unproven) in efforts to improve patient outcomes, EMS systems should aggressively coordinate care and systematically go after “low hanging fruit.”
Technology in itself isn’t a blanket solution. It should be tightly integrated with providers and the system’s response algorithms to offer a benefit. For example, an important early step in improving cardiac arrest outcomes in a particular community may be to invest in interagency training and ensure all providers are well versed in high-performance CPR. This should include integration that consistently demonstrates a chest compression fraction rate of greater than 80%.
To parallel this example to prehospital ultrasound, one must be able to walk before running. Ultrasound is a tool for the advanced practitioner and system (BLS providers can be advanced in regard to their medical decision-making and select skills depending on their area of operation).
Being well-versed in ultrasound indications, understanding how it can help refine medical decision-making, incorporating it algorithmically and directly into protocols, and ultimately having a longitudinal quality assurance program for continued practice and onboarding of new personnel are precursors to a successful program.
The indications for prehospital ultrasound parallel the increasing utility of point-of-care testing seen broadly in the ED. (See Table 1.) Some have hypothesized that ultrasound can be applicable in up to one-sixth of EMS patients, while not delaying treatment or transport to receiving centers given relatively short exam times.6
In a review of the current use of prehospital ultrasound, the authors suggest that, “Ultrasound with rugged, portable technology could be used to augment physical examination and has the potential to increase diagnostic capability for prehospital providers.”
Prehospital medicine relies on making an operational differential diagnosis to begin triage and treatment for patients with limited history and a narrow exam.7 Field trials suggest paramedics can adequately obtain and interpret images gathered in the prehospital environment, striking an important first step in delivering this modality from the in-hospital environment.8
The most studied exam type in EMS is the focused assessment of sonography in trauma (FAST), which is used to identify hemoperitoneum (i.e., blood in the abdomen). In one prospective study using prehospital ultrasound, a series of 202 trauma patients were examined and the sensitivity, specificity and accuracy of prehospital FAST were 93%, 99% and 99% respectively, in comparison to physical exam at the scene 93%, 52% and 57%.9
Blood or fluid in the abdomen was detected in 14% of patients and use of prehospital ultrasound led to a change in management for 30% of cases and a change in hospital destination in 22% of cases.9 This is a significant finding and demonstrates real-world application and validity for ultrasound usage.
In another prospective study examining 230 medical patients receiving either CPR or in various shock states (sustained hypotension), prehospital ultrasound led to a change in management as well as to improved diagnostic capability. In 35% of arrest patients presenting with asystole on the monitor, as well as 58% of those with PEA, coordinated cardiac motion was in fact detected, and the implementation of prehospital ultrasound was associated with statistically increased survival.
Data obtained while scanning these critically ill patients led to a change in management in a staggering 78% of cases, leading the authors to conclude that ALS-compliant point-of-care ultrasound “is feasible, and alters diagnosis and management in a significant number of patients.”10
Given the trend of increased use of ultrasound during resuscitation in critical care and emergency medicine, and the introduction of more portable, durable devices, there’s a natural inclination to explore the potential applications of prehospital ultrasound.
A 2014 survey of EMS medical directors conducted by the National Association of EMS Physicians (NAEMSP) found that although only 4.1% of current systems implemented prehospital ultrasound, an additional 21.7% are considering implementation. The authors highlighted that providers can use ultrasound to obtain “immediate anatomical, diagnostic and functional information for their patients.”11
Reasonably, most medical directors surveyed desired further research showing the utility of prehospital ultrasound in reducing patient morbidity and mortality. They also cited equipment and training costs as challenges to implementation. (See Table 2.)11
Despite the hurdles inherent in the prehospital environment, such as attempting to scan in the back of a moving ambulance, noncompliant patients, variable ambient lighting, and an inconsistent power source, research from the United Kingdom indicates ultrasound could be performed to a standard consistent with those performed in the hospital ED.12
Nevertheless, further research needs to be done on the specific presenting complaints, call types, and the potential exam types where ultrasound might improve diagnostic accuracy and, ultimately, improve patient outcomes while not adding to scene or transport time.
The Training Imperative
The successful incorporation of ultrasound in a prehospital setting requires a paradigm shift in our approach to critically ill and injured patients. This must include a robust training program that mandates education and careful implementation amongst the providers who would employ the modality.
High-quality training, including in-situ simulation, helps to firmly embed the principles of a particular technology within a provider’s medical decision-making.
If specific prehospital ultrasound algorithms could also be inserted into a service’s protocols it would also serve as an additional reminder for providers to perform the examination as time and circumstance allow.
Given that most of the literature for prehospital ultrasound is derived from European systems implementing the Franco-German crew resource management model—commonly staffed by a critical care physician—a recent systematic review focused on prehospital ultrasound curricula designed specifically for paramedics, attempting to probe optimal content, duration, setting, design and evaluation.
The authors noted many out-of-hospital algorithms that are being successfully implemented by providers, including FAST, obtaining pleural windows to screen for pneumothorax and pulmonary edema, as well as detecting early stroke and the assessment of hemodynamic status. The authors concluded that “FAST and pleural ultrasound is feasible and time effective with successful application;” whereas, “curricula designed to detect cardiac standstill have been too short.”13
As reported in the literature, the duration of the abdominal ultrasound curricula has varied widely, from four hours over one day to 13 hours over two months of training, with most curricula using a 1-day course. The duration of pleural ultrasound curricula is typically shorter than FAST, and studies have suggested that image acquisition is a separate skill from image interpretation.14
Paramedics can also be taught to interpret thoracic ultrasound in as little as 10 minutes with significantly higher diagnostic accuracy than one might imagine.15
Comprehensive studies combining imaging acquisition and interpretation taught pleural ultrasound curricula from 25 minutes to 10 hours. Interestingly, one study showed 26% of patients receiving a needle thoracostomy for a suspected pneumothorax in the field had a positive sliding lung sign upon arrival, suggesting the patient didn’t have a pneumothorax and prehospital ultrasound might have prevented an unnecessary invasive procedure and potential harm to the patient.16
It’s important to note, however, that the minimum competency level and number of scans required to achieve competency in prehospital ultraound haven’t yet been established.17
The American College of Emergency Physicians (ACEP) presents a more firmly established parallel for resident physicians graduating from accredited emergency medicine programs, recommending 25–50 cases per individual ultrasound application.18 Although this may be a challenging target to hit for EMS agencies implementing prehospital ultrasound, it does represent a standard for best practice which may warrant further investigation.
Initial ultrasound skill acquisition by paramedics is possible with relatively short training courses. Skill maintenance in ultrasonography, similar to other critical care skills, requires routine practice, good quality assurance programs and physician oversight.
POCUS has become a standard of care in relatively short order across EDs nationwide, with prehospital ultrasound becoming increasingly more common in Europe, where they’ve found ultrasound to be valuable in the field.
Prehospital ultrasound has many clinical applications that may reduce morbidity and potentially improve outcomes for patients with life-threating conditions.
In addition to helping a provider make an accurate and specific diagnosis with accuracy, prehospital ultrasound also has the potential to change treatment in the prehospital sphere, alter the destination or receiving facility, as well as the potential to alter the receiving hospital management of the critically ill or injured patient.
The initial adoption of this technology will likely be highest in critical care subsets of out-of-hospital providers, such as air medical and ground critical care transport units, but potentially shows a broad-based application in 9-1-1 emergency response at the ALS and BLS levels.
In addition to the need for further prospective outcomes research examining potential algorithms, as well as their effect on patient morbidity and mortality, some EMS agencies and their medical directors are concerned about the cost of ultrasound units and the need for additional training for their personnel.
The cost for portable ultrasound units has declined, and several manufacturers now have, or will soon offer, ultrasound integrated into their existing cardiac monitor packages. Like 12-lead education, services desiring to implement ultrasound into their clinical operation should do so with proper training that ensures maximum effectiveness.
As with any new technology, it’s not the shiny new tool which leads to benefit, but rather the upgrade to the provider’s medical decision-making algorithm. The ability to acquire otherwise invisible physiologic and anatomic information about a critical patient at the scene simply can’t be understated.
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