Wednesday, April 15, 2015

Does cardiac standstill on bedside echo equal 100% mortality?

You’re in the midst of catching up on notes during a hectic overnight shift when out of the corner of your eye you see a stretcher zoom into the trauma bay – with an EMT leaning over the side performing chest compressions. As the team gathers, the paramedics give report. The patient is a middle-aged male, no known past medical history, who was acting normally about half an hour ago when he suddenly collapsed in front of his family. They started CPR within a couple minutes of the patient collapsing, and called EMS. The paramedics continued CPR, placed a supraglottic airway, and placed the patient on the monitor. He has had a slow, organized rhythm without pulse throughout the arrest. He has received several doses of epinephrine without response. The patient has been pulseless for a little over half an hour by the time he arrives. The ED crew takes over CPR, IV access is obtained, and the patient switched over to the ER monitors, which show a slow, wide-complex, relatively disorganized rhythm. The patient shows no signs of life. Your attending physician calls for the ultrasound, and calls out to the team that if the bedside echo shows cardiac standstill, you will consider terminating further resuscitative efforts.

Clinical Question:

Does cardiac standstill on bedside echo universally predict mortality in OHCA?

Literature Review:

A systematic review of studies investigating the diagnostic accuracy of bedside echo in OHCA was published by a Canadian group in Annals in 2012 [1]. This was a well-done study, with a broad search strategy, rigid but logical inclusion & exclusion criteria, and quality assessment with a modified version of the QUADAS instrument.
Eight studies were included in the final analysis, with a total of 568 patients. Of the 378 patients with cardiac standstill on bedside echo, only 9 (2.4%, 95% CI 1.3% – 4.5%) achieved ROSC. The authors pooled results of the included studies to devise a 2x2 table and determine test characteristics of bedside echo. This revealed a sensitivity of 91.6% (95% CI 84.6% - 96.1%) and specificity of 80.0% (95% CI 76.1% - 83.6%). The positive likelihood ratio is 4.26 (95% CI 2.63 - 6.92) and the negative likelihood ratio is 0.18 (95% CI 0.10 - 0.31). Heterogeneity was minimal (0.0%) for the negative likelihood ratio, but was significant (82.1%) for the positive likelihood ratio. The authors conclude, “While there is insufficient evidence to support using echo in isolation to decide whether or not to continue with cardiopulmonary resuscitations, the presence or absence of VWM in the context of the pretest survival likelihood can provide emergency personnel with further information to assist making that difficult decision whether to stop cardiopulmonary resuscitation with more confidence.”

It is important to note that the outcome of interest in this systematic review was survival to admission, which is not necessarily a good predictor of neurologically-intact long-term survival past discharge, which is the ultimate patient-centered outcome of OHCA. Further limitations included variable inclusion/exclusion of traumatic arrest patients in the included studies, and variability in application of bedside ultrasound. Namely, there were significant differences in training level of examiners, degree of external review of OCHA studies, and definition of “cardiac standstill” between the included studies.
This paper was the focus of a “Systematic Review Snapshot,” authored by our very own Dr. Brian Cohn and published in Annals in 2013 [2].

I attempted a PubMed search using the same search strategy as the authors in the original systematic review (available in the online supplementary material), but I did not discover any further studies on this topic that have been published since that paper in 2012.

Take-home Points:

- Cardiac standstill does not universally lead to failure of resuscitation of OHCA.
- The best-available current evidence does not support the use of bedside echo alone to predict outcomes in OHCA patients.
- Other factors influencing likelihood of neurologically-intact survival (down time, underlying rhythm, patient age/comorbidities, etiology of arrest, etc.) should be taken into account when interpreting bedside echo results.
- More research is needed to determine true prognostic factors associated with survival from OHCA.

Submitted by C. Sam Smith, MD. @CSamSmithMD
Faculty review by Brian Cohn +EMJClub 

[1] Acad Emerg Med. 2012 Oct;19(10):1119-26.
[2] Ann Emerg Med. 2013 Aug;62(2):180-1.

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