The annual EMS State of the Sciences Conference, colloquially known as the “Gathering of Eagles,” is held to share the most cutting-edge information and advances in EMS patient care, research and management issues, trending challenges and lessons learned. Speakers include medical directors from the EMS systems of America’s largest cities, plus prestigious physician guests.
A pair of presentations at the 2015 Gathering looked at expanding the use of ultrasound technologies into the prehospital arena for patients in cardiac arrest.
Using Prehospital Ultrasound for Cardiac Resuscitation
Presentation: Ultrasound in Prehospital Cardiac Resuscitation. Presented by Drew Harrell, MD, Medical Director, Albuquerque Fire Department, Associate Director, UNM EMS Medical Direction Consortium
Drew Harrell, MD, medical director for the Albuquerque Fire Department and associate director of the University of New Mexico EMS Medical Direction Consortium, discussed utilizing part of an existing trauma-based ultrasound procedure to help guide care of patients in cardiac arrest. His session, “Ultrasound in Prehospital Cardiac Resuscitation,” began with acknowledging the key role prehospital providers play in that effort.
Harrell said EMS has a history of being early adopters of new technologies or transferring technologies proven in emergency departments to the prehospital setting. In the early 1990s, he noted, there was a groundswell of interest in new technology, but much of it didn’t stick—possibly because it was not used in the correct areas. He believes focusing on prehospital cardiac arrest can bring better results.
“Cardiac arrest is one prehospital disease process where the entirety of initial resuscitation occurs outside the emergency department,” Harrell said. “We own that patient from the time of the event until return of circulation.”
Harrell believes the FAST (focused assessment with sonography for trauma) examination is a starting point for moving ultrasound into the field. FAST is a helpful, noninvasive means of identifying fluid where it does not belong in trauma patients. When examining with ultrasound in the subxiphoid position, the operator can observe the presence of any pericardial fluid and how much “squeeze” effect the heart is producing.
Harrell said one common indicator for use would be where a patient is showing pulseless electrical activity (PEA): “We often have the hardest time on patients with extended PEA. If we could look and find additional signs to support continued care, we could better serve the patient. We could change methods and pharmaceuticals to be more appropriate to the patient’s needs.”
Another condition where being able to image the heart movement with ultrasound would be useful is in what Harrell called really, really fine asystole. “Ultrasound offers huge opportunities to make better treatment decisions,” he said.
Harrell cited a 2010 study from Hennepin County, MN, where paramedics were trained in FAST and aortic aneurysm ultrasound examination techniques in a six-hour course. During the study, 104 patients who were being transported for cardiac conditions were examined by paramedics during transport, after all other emergency care was provided. Follow-up reading by physicians agreed with 100% of the medics’ exam interpretations. Most important, according to Harrell, was that pericardial fluid was found in 7% of the exams, potentially leading to altering patient care.
“That study shows there certainly is an opportunity. The results speak volumes to the fact that it’s technically doable in the field and trainable for field use,” Harrell said.
A 2014 survey of National Association of EMS Physicians EMS directors showed 22% of respondents considering using ultrasound in the prehospital setting. Harrell said the devices are becoming more durable and cost-effective, which adds to the allure. “When we can get more than one device that can be used over and over for less money than a single heart monitor, it really changes the calculus for EMS systems,” he said, adding that one day we may look at ultrasound the same way we once did pulse oximetry and AEDs.
Harrell said it is important to keep looking at patient care, emerging technologies and how we can use technology to improve patient outcomes. “Right now we don’t even know what we don’t know,” he said.
“Can ultrasound be taught and fielded successfully? Let’s find out. We own prehospital cardiac arrest. This is what we do. These are the patients on whom we are most likely to make the most difference.”
Presentation: TEE-ing Off the Cardiac Arrest Sand Trap: Shadow-Boxing for CPR Vectors, Missed VF & Pseudo PEA. Presented by Scott T. Youngquist, MD, MSc, Medical Director, Salt Lake City Fire Department.
Scott Youngquist, MD, MSc, is medical director for the Salt Lake City Fire Department. He has been examining the potential for prehospital use of a different type of ultrasound technology: transesophageal echocardiography (TEE).
His Gathering of Eagles presentation was titled “TEE-ing Off the Cardiac Arrest Sand-Trap: Shadow-Boxing for CPR Vectors, Missed VF & Pseudo PEA.” It discussed how using TEE to directly visualize the heart during cardiac arrest might address some limitations of field assessment and treatment. What impact would there be if prehospital providers could, in effect, see structures and movement inside the body?
Youngquist said the idea came as a result of work Mike Mallin, MD, did developing an emergency ultrasound program at the University of Utah. Youngquist said he has a strong interest in both echocardiography and cardiac arrest treatment. “We use TEE in the emergency department,” he asks. “Why can’t we use it in the field?”
TEE is a test that uses sound waves to create high-quality moving images of the heart and its blood vessels. A flexible tube is inserted down the patient’s throat into the esophagus. A transducer at its tip generates images that show the size and shape of the heart, as well as how the chambers and valves are working. TEE can identify areas of heart muscle that are not working properly and detect possible clots, pericardial fluid buildup and problems with the aorta. Because the esophagus is directly behind the heart, highly detailed images are possible.
Youngquist believes TEE has the potential to improve rhythm analysis by identifying masked ventricular fibrillation and distinguish PEA from pseudo-PEA. He said it can also replace the pulse check with a faster, more accurate visualization of whether the heart is still or has experienced return of spontaneous circulation.
“TEE can prevent withholding appropriate care during long searches for pulses,” Youngquist said. “The movement of the heart is readily observable, leading to faster and more accurate treatment decisions.”
Youngquist said using TEE can also improve hand placement for more effective compressions. He referenced an ED-based study on cardiac output using hand compressions conducted on patients with PEA but no heart motion. Forty-four percent of the time, hand placement was actually occluding aortic outflow.
“Given the anatomic variations in patients, a one-size-fits-all hand placement may not be optimal,” he said. “It appears that a lower sternum placement provides better cardiac outflow than the inter-nipple hand placement.”
It remains uncertain at this time whether TEE can help classify the cardiac rhythm, but Youngquist said there have been reports of arresting patients showing asystole on the monitor, yet VF activity with a TEE probe. He cited the case of one who was shocked, leading to ROSC. “We don’t know how accurate modern monitors are for determining VF versus asystole,” he said.
PEA shows organized rhythm on the monitor but can be a wide range of nonsurvivable conditions. In pseudo-PEA the heart is pumping, but ineffectively. The prognosis is different depending on if the heart is standing still versus showing activity.
“TEE may help prevent stopping resuscitation prematurely,” Youngquist said. “Of course, the condition of the heart is not the only consideration. For example, what is the condition of the patient’s brain?”
Using TEE to identify the cause of arrest has ramifications on patient management. Youngquist cited a study where TEE correctly identified the arrest cause in 65% of patients. For 31%, this changed how they were managed. Youngquist said TEE can reveal signs of pulmonary embolism, cardiac tamponade, aortic rupture, aortic dissection, papillary muscle rupture and hypovolemia. Wall motion during compressions can identify tissue damaged by myocardial infarction.
Youngquist said field use of TEE is not right around the corner. Key research yet to be done includes gathering more observational data on the epidemiology of PEA.
Ed Mund began his fire and EMS career in 1989. He currently serves with Riverside Fire Authority, a fire-based ALS agency in Centralia, WA. His writing and photos have appeared in several industry publications. Contact him at email@example.com.