By Mark Magee, MD & Allison Zanaboni, MD
The use of transthoracic echocardiography (TTE) in cardiac arrest has stirred controversy recently following the publication of literature discussing potential harms of the modality during resuscitation. While official ACLS guidelines do not call for utilization of point-of-care ultrasound (POCUS), it has become an increasingly common component in the care of patients in cardiac arrest. In fact, in 2010 ACEP and the American Society for Echocardiography released a joint statement supporting the use of ultrasound in cardiac arrest.1 Nevertheless, no consensus exists to guide the use of ultrasound in cardiac arrest, leading to inconsistent and variable application.
The controversy became apparent in July of 2017 when a group from the University of Maryland published an article entitled “Ultrasound use during cardiopulmonary resuscitation is associated with delays in chest compressions.” In their prospective cohort study of 23 patients, they found that pulse checks performed with TTE averaged 21.0s versus 13.0s for those without ultrasound, accounting for a statistically significant delay of 8.4s in the resumption of compressions.2 When considering that current guidelines recommend no more than 10s of time “off-chest,” their results are understandably concerning. This has led to many discussions of the appropriate use of ultrasound during code management, with some questioning its utility at all.
However, it is essential to consider several limitations of this study. First, despite the statistically significant difference in the primary endpoint of time “off-chest,” its relation to a true patient-centered outcome is unknown, as this study found only one patient surviving to hospital discharge. Second, while a delay in chest compressions was apparent, the group managed without POCUS also averaged a duration greater than current recommendations (13.0s versus 10s).2 Furthermore, the underlying rhythm was unclear in the enrolled patients. This is particularly significant considering the potential greater importance of ultrasound in management of patients with non-shockable rhythms. Finally, there were no patients who were found to have an immediately reversible cause of arrest using ultrasound, such as cardiac tamponade or tension pneumothorax. In such clinical scenarios point of care ultrasound has demonstrated considerable benefit.3-5 Furthermore, the study does not account for the sonographic training of the providers performing the ultrasound. Likewise, how the ultrasound was performed is not described. Ideally, the most skilled sonographer should be handling the ultrasound taking brief clips to review as chest compressions are resumed. This will minimize interruptions.
As alluded to in the previous paragraph, research has proven that ultrasound is an invaluable component of code management, particularly in patients with pulseless electrical activity (PEA) and asystole. In 2016, the long-anticipated REASON trial was published.3 This large, multi-center, prospective, observational study of 793 patients aimed to determine if the presence of cardiac activity on bedside ultrasound was associated with improved survival. Patients who presented to the ED in cardiac arrest or who lost pulses in the department and had an initial rhythm of either PEA or asystole were enrolled. Patients who had a brief resuscitation or termination of efforts based on a standing DNR were excluded. Various patient and presentation factors were evaluated in the trial, including age, presence of a shockable rhythm during the resuscitation, downtime, bystander CPR, and presence of cardiac activity on ultrasound, which was defined as “any visible movement of the myocardium, excluding movement of blood within the chambers or isolated valve movement.”3 The study demonstrated that the finding of cardiac activity was most strongly associated with survival at all studied time points. Furthermore, the absence of cardiac activity carried a 0.99 PPV for non-survival to hospital discharge.3 The study also identified a small group of patients in whom ultrasound led to non-standard ACLS management strategies (pericardiocentesis, thrombolysis) and whose survival was significantly greater than the average cardiac arrest patient.
As such, it is clear that POCUS maintains a clinically significant role in the management of cardiac arrest. Admittedly, the REASON trial was limited by potential bias, given providers may have been more comfortable ending resuscitative efforts in patients without cardiac activity, but this is not the first trial to highlight the poor outcome amongst this group.3 Furthermore, the study highlighted the ability of POCUS to identify causes of arrest in which bedside procedures or non-standard medication administration proves life-saving. And while use of ultrasound may increase time “off-chest,” current literature supports limiting its use to the initial pulse/rhythm check and again at termination of efforts, thus minimizing its effect on compression fraction.
Ultimately, this debate may be for naught, owing to the rise in support for ED-performed transesophageal echocardiography (TEE). While the concept of POCUS TEE is not novel (including to this column, see June 2015 Fellows Corner: TEE anyone?), its use has been bolstered by an ACEP position statement published April, 2017.6 It has the clear benefit of maximizing compression fraction in relation to obtaining ultrasound images, as a continuous view of the heart can be obtained throughout resuscitation. Given that ability, it provides the added benefit of monitoring the effect of compression on the heart, allowing accurate hand placement to ensure maximal effect on the left ventricle while avoiding outflow obstruction. Overall, current literature remains limited regarding the utility of TEE in cardiac arrest, however it is an exciting application that may prove invaluable to the future of code resuscitation.7-9
It is clear that POCUS remains an essential component of the Emergency Medicine physician’s care of patients in cardiac arrest. Future research will hopefully define what ultrasound’s appropriate role is and how its utility can be maximized. For now, the modality will continue to guide resuscitative management and provide indications for the use of non-standard ACLS interventions.
Ocular ultrasound: EM physicians are OK but not perfect at diagnosing common pathology.
By Joshua Guttman, MD
Baker N, Amini R, Situ-LaCasse EH, et al. Can emergency physicians accurately distinguish retinal detachment from posterior vitreous detachment with point-of-care ocular ultrasound? Am J Emerg Med. 2017 Oct 13. pii: S0735-6757(17)30814-8.
Ocular complaints are common in the ED. Particularly, it is common for patients to present with visual disturbance, flashes and floaters. The most common causes of these complaints are posterior vitreous detachment and retinal detachment. Posterior vitreous detachment (PVD) is a relatively benign cause that does not require urgent ophthalmologic intervention, while retinal detachment (RD) is a site-threatening and requires urgent consultation. Traditionally, emergency physicians relied on a dilated ophthalmologic exam by an ophthalmologist to differentiate between these two conditions. Ultrasound has been suggested as an alternative method that can be performed at bedside, without the aid of an ophthalmologist. Previous studies on experts showed that point of care ultrasound (POCUS) was able to rule out RD with a high degree of accuracy. Ultrasound can also be used to identify PVD, differentiating it from RD.
The authors of this study sought to determine the ability of emergency physicians at various levels of POCUS experience to differentiate RD, PVD and normal ocular POCUS based on video image review. They enrolled residents and attendings who all had basic POCUS knowledge but had variable proficiencies in ocular POCUS. They were all given a brief tutorial on differentiating PVD and RD. The gold standard was the diagnosis given by the consulting ophthalmologist for those specific cases. Overall, 390 video clips were reviewed by 13 physicians. They diagnosed RD 74.6% of the time, PVD 85.7% of the and normal 94.9% of the time. There was no statistically significant difference between physicians with more or less experience (0-25 scans vs 25-50 vs over 50) or by level of training (attending, fellow or resident).
This study showed that emergency physicians had modest accuracy at differentiating PVD and RD on ultrasound. There were several limitations to this study, including the limited number of participants, the bias towards only 3 possible diagnoses on POCUS (PVD, RD and normal) as opposed to the wider differential diagnosis in normal clinical practice, and that it was run at an academic medical center with likely more savvy POCUS staff. The more interesting aspect of this study was that there was no difference in accuracy based on the number performed. It is generally assumed that the more POCUS exams done, the more proficient one is at interpretation. However, in the case of ocular ultrasound this may not be accurate. Fortunately, emergency physicians at all levels were able to diagnose a normal ocular ultrasound which can be helpful in the clinical setting. However, the moderate diagnostic accuracy is not sufficient to rule out RD and therefore a non-expert still needs ophthalmologic consultation.