Prehospital Ultrasound in Undifferentiated shock, Cardiac Arrest, and the End of Resuscitation.

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Prehospital Ultrasound in Undifferentiated shock, Cardiac Arrest, and the End of Resuscitation.

Nicholas Jackson

Southern Maine Community College

For years ultrasound was an imaging modality for sonography technicians who acquired them and the radiologist who reviewed them. With the rapid rate technology has evolved and developed we now have point of care ultrasound. Point of care ultrasound allows physicians in the emergency department and office setting to acquire diagnostic quality imaging at the bedside. While physicians have a vast array of transducers, protocols, and views The question remains, Can paramedics perform the same feats to help our patients? In this paper we will review the “Focused echocardiographic evaluation in life support (FEEL)” protocol, the “Prehospital Evaluation of Effusion, Pneumothorax, and Standstill (PEEPS)” protocol, and assessment of non shockable rhythms under ultrasound.

According to the AHA, in the United States alone an estimated 424,000 people are assessed by EMS while in cardiac arrest every year; Of those people only 5.2% survive (Go et al., 2014). While Early CPR and defibrillation has been a major emphasis in prehospital care we may be able to benefit patients in cardiac arrest using ultrasound. New techniques and technologies are constantly being added and evaluated for emergency medicine. Just years ago end-tidal capnography was set as the standard of care for intubated patients and we’ve learned to evaluate our resuscitative efforts based on it. Before that the 12 lead electrocardiogram was introduced to the prehospital field. Initially it was strictly interpreted by the physicians at the receiving hospital; Now paramedics have the education and training to announce a ST-segment elevation myocardial infarction to the hospital, activate catheterization laboratories for percutaneous coronary intervention, and actually make a difference in patient care and flow. While this is entirely theoretical I would argue that ultrasound has the utility and functionality to be the next major advancement in prehospital emergency medicine.

Breitkreutz et al. trained prehospital emergency physicians in the focused echocardiographic evaluation in life support (FEEL) exam. They then started a protocol for the EPs to perform the FEEL exam on patients in cardiac arrest and peri-resuscitation in the prehospital environment. The FEEL exam had them look at the heart via four different views, parasternal long axis, parasternal short axis, apical 4 chamber, and subcostal. These four view enabled them to rule in or out some of the significant reversible causes of arrest like myocardial insufficiency (right or left ventricle dysfunction and myocardial ischemia), pericardial effusion, pulmonary embolus, and hypovolemia (Breitkreutz et al., 2010).

Breitkreutz et al. found ultrasound in the pre-hospital setting made a significant difference in patient care while in cardiac arrest or shock, even in the hand of inexperienced providers:

This study demonstrates that FEEL can be performed in the pre-hospital setting, resulting in the diagnosis of a significant number of potentially treatable underlying conditions and subsequent alteration in patient management.The use of echocardiography or ultrasound by novice practitioners has been shown to be feasible in the emergency setting,with success in obtaining images and interpretation leading to a reduction in the differential diagnosis. Further, focused echocardiography has been shown to improve the diagnostic accuracy of shocked patients even when undertaken by relatively inexperienced practitioners. (2010, p. 1531)

While this seems like a glowing review for prehospital ultrasound it is slightly confounded due to the difference in systems. The German system utilizes physicians in the prehospital environment. This paper indicates that prehospital ultrasound in cardiac arrest can be beneficial and is even feasible; It doesn’t state that paramedics are capable of similar feats. It isn’t unreasonable to expect paramedics to be able to learn how to utilize ultrasound just as these physicians. In fact this study utilized “novices” in ultrasound acquisition and interpretation. Luckily this was addressed recently.

(Bhat et al., 2015) performed a study utilizing paramedic and EMT students from two Californian training centers. They gave them images and clips of ultrasound taken by trained physicians in a local ED. They tested their cohort of prehospital providers on their ability to identify pericardial effusion, pneumothorax, and cardiac standstill as they stood. They then received a single hour of didactic training on ultrasound imaging in the described pathologies. After the class they took a similar test to assess for the pathologies. Pretest scores had a mean value of 65.2% and after the class the mean value was 91.1%. While it is a limited assessment for the prehospital environment, It can be clinically significant. Especially when in reference to the controversial subject of true pulseless electrical activity, pseudo pulseless electrical activity, and when to stop resuscitation.

Prognostication of a patient in a medical cardiac arrest is extremely difficulty. Currently the standard of care in the prehospital setting is to follow ACLS protocols in the field until ROSC or 20 minutes has elapsed in a non shockable rhythm (PEA or asystole). I believe prehospital ultrasound could change that paradigm. Cardiac standstill on ultrasound had a positive predictive value of 97.1% for death . While the Authors go on to say that to implement such a protocol would require significantly more study it does make sense to use as a stop point (Aichinger et al., 2012). In asystolic arrest and lack of cardiac motion termination of resuscitation could be considered in the future after a shorter time of ACLS. However, if cardiac motion is still present continued resuscitation may be indicated. While no research has proven this yet the initial research appears promising.

Pulseless electrical activity, the only rhythm on the ACLS pretest that tells you what it is. Is it that simple? Unfortunately PEA is not as easily reversed as ventricular tachycardia or fibrillation due to the fact that the electrical system is technically appropriate. The AHA guideline encourage us to fine “reversible causes” of PEA with the “H&T’s” mnemonic. However a new algorithm was suggested by Littmann, Bustin, and Haley. They propose that PEA is should be divided into narrow complex and wide complex PEA and further evaluation should focus on relatable causes. They suggest NCPEA should be evaluated and treated as a mechanical failure, while WCPEA should be evaluated and treated as metabolic or ischemic failure. The AHA guidelines tell us to treat reversible causes but they do not give good direction on how to assess that. Littmann et al. suggest ultrasound. In the four most common causes of NCPEA (cardiac tamponade, tension pneumothorax, mechanical hyperinflation, and pulmonary embolism) patients were in pseudo-PEA, or had left ventricle action but no palpable pulse.  (2014)  In other words, they had a beating heart in a profound shock state. Which could easily confound prehospital providers into continuing on scene resuscitation in a patient that could be aggressively resuscitated while transporting to definitive care. Theoretically, this population requires aggressive shock treatment like aggressive IV fluids, Inotropic therapy, or thrombolysis more than they need CPR and to be left for dead at the scene. Does this effect prehospital management? Should paramedics be assessing cardiac arrest patient with ultrasound?

I would argue yes. As we’ve seen prehospital ultrasound does benefit clinicians in diagnosing causes of shock and cardiac arrest. We’ve proven that paramedics can be trained to accurately assess pathologies with reasonable educational requirement. We’ve also seen evidence in on when resuscitation is futile and evidence suggesting when maximally aggressive treatment and transport may be indicated. Only 5.2% of people with EMS assessed OHCA survive. While I have no evidence supporting mass adoption of prehospital ultrasound I believe that for the reasons stated above it is rightfully growing in popularity and should be considered.

As technology evolves and the role and knowledge of paramedics grows the ability to perform accurate POCUS will mean having imaging methods that have been proven in the ED and other acute care settings in the hospital. I would argue that just as emergency medicine has had to fight for its right to advance its practice and add life, limb, and dollar saving interventions to its algorithm, we as prehospital providers must fight for and earn the skills and technology to do the best by our patients. By adding ultrasound to the assessment of cardiac arrest and severe shock patients we can potentially recover lives that were previously lost.

References

Aichinger, G., Zechner, P. M., Prause, G., Sacherer, F., Wildner, G., Anderson, C. L., … Fox, J. C. (2012). Cardiac movement identified on prehospital echocardiography predicts outcome in cardiac arrest patients. Prehospital Emergency Care: Official Journal of the National Association of EMS Physicians and the National Association of State EMS Directors, 16(2), 251–255. http://doi.org/10.3109/10903127.2011.640414

Bhat, S. R., Johnson, D. A., Pierog, J. E., Zaia, B. E., Williams, S. R., & Gharahbaghian, L. (2015). Prehospital Evaluation of Effusion, Pneumothorax, and Standstill ({PEEPS)}: Point-of-care Ultrasound in Emergency Medical Services. The Western Journal of Emergency Medicine, 16(4), 503–509. http://doi.org/10.5811/westjem.2015.5.25414

Breitkreutz, R., Price, S., Steiger, H. V., Seeger, F. H., Ilper, H., Ackermann, H., … Walcher, F. (2010). Focused echocardiographic evaluation in life support and peri-resuscitation of emergency patients: A prospective trial. Resuscitation, 81(11), 1527–1533. http://doi.org/10.1016/j.resuscitation.2010.07.013

Go, A. S., Mozaffarian, D., Roger, V. L., Benjamin, E. J., Berry, J. D., Blaha, M. J., … Turner, M. B. (2014). Heart Disease and Stroke Statistics—2014 Update: A Report From the American Heart Association. Circulation, 129(3), e28–e292. http://doi.org/10.1161/01.cir.0000441139.02102.80

Littmann, L., Bustin, D. J., & Haley, M. W. (2014). A simplified and structured teaching tool for the evaluation and management of pulseless electrical activity. Medical Principles and Practice: International Journal of the Kuwait University, Health Science Centre, 23(1), 1–6. http://doi.org/10.1159/000354195