The Speed of Sound: Ultrasound Predicts Cardiac Arrest Survival

Butts, Christine MD

Emergency Medicine News:
doi: 10.1097/01.EEM.0000511949.25348.93
The Speed of Sound
Author Information

Dr. Butts is the director of the division of emergency ultrasound and a clinical assistant professor of emergency medicine at Louisiana State University at New Orleans. Follow her on Twitter @EMNSpeedofSound, and read her past columns at http://bit.ly/EMN-SpeedofSound.

Article Outline

Much has been written about resuscitation in cardiac arrest. Changes to CPR techniques, tracking end-tidal CO2 monitoring, and therapeutic hypothermia have been hot topics over the past several years. We are constantly searching for new and more effective ways to achieve return of spontaneous circulation (ROSC) in our patients.

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But what does science say about when to end resuscitation efforts? Is there some clear point at which efforts are so unlikely to be successful that it is futile to continue? Certainly, each of us has an opinion on that based on our own experience and ethics.

A completely unscientific poll of my colleagues on a recent work day yielded multiple different answers. The variables mentioned included the patient's age, the presumed underlying cause of the arrest, the downtime, whether the arrest was witnessed, and physiologic factors such as end-tidal CO2 readings.

All of my colleagues agreed, however, that the presence or absence of cardiac activity on bedside ultrasound was key in determining when to stop resuscitation. Certainly, seeing coordinated myocardial contractility at a pulse check is reassuring, but what about seeing minimal or no cardiac activity? What's the next step for these patients?

Several small studies have evaluated the role of ultrasound in cardiac arrest. A 2012 meta-analysis pooled eight of these studies and found that only 2.4 percent of patients without ventricular wall motion went on to have ROSC. (Acad Emerg Med 2012;19[10]:1119.) Conversely, 190 of the 538 patients enrolled in these studies had ventricular wall motion on echo, and 98 of these had ROSC (51.6%). This meta-analysis looked at studies from 2001 to 2012 with variable methods, and included traumatic and nontraumatic arrests. Certainly, these findings would argue that lack of cardiac motion indicates a poor likelihood of successful resuscitation.

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Definitive Predicting Tool

A more recent study published in the journal Resuscitation in October added more food for thought. (2016;109:33.) Nearly 800 patients at multiple hospitals with atraumatic asystolic or PEA arrest were enrolled in a prospective, observational trial. Cardiac ultrasound was performed at the start and end of resuscitation, with a primary outcome of survival to hospital admission and ROSC and survival to hospital discharge as secondary outcomes.

Perhaps not surprisingly, the authors found that the majority of patients without cardiac motion on ultrasound failed to survive to admission, let alone achieve ROSC. Fourteen percent of these patients, however, had ROSC, which is a marked increase over what was found in the previous meta-analysis. The exclusion of patients with traumatic cardiac arrest may have some role in explaining this difference, but the finding is still worth noting. Another important finding in this study was pericardial effusion in 34 patients. Thirteen in this group had pericardiocentesis and demonstrated a markedly higher survival to hospital discharge (15.4%) than the general group (1.6%).

Where do these studies leave us? Certainly, ultrasound has a role in evaluating and managing patients with cardiac arrest. The potential to identify a treatable cause, such as pericardial tamponade, is reason enough. The jury is still out, though, when it comes to determining when to stop resuscitation.

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