Cardiac & Resuscitation, Columns, Patient Care, Special Topics

Study on Cerebral Oxygenation in Cardiac Arrest Patients Lacks EMS Implication

Issue 8 and Volume 40.

THE RESEARCH
Genbrugge C, Meex I, Boer W, et al. Increase in cerebral oxygenation during advanced life support in out-of-hospital patients is associated with return of spontaneous circulation. Crit Care. 2015;19:112.

THE SCIENCE
Researchers attempted to correlate cerebral oxygenation (rSO2) and return of spontaneous circulation (ROSC) by using a device that performs cerebral near-infrared spectroscopy (NIRS). The device they used is called the Equanox and is manufactured in the United States by Nonin Medical in Plymouth, Minn. This technology, which has been in use for many years in the operating room to monitor rSO2 during cardiovascular surgery, has only recently been studied in cardiac arrest.

An emergency medicine physician responded to prehospital cardiac arrest victims and applied the device to the forehead of the 49 patients. rSO2 was then recorded throughout the resuscitation.

Patients with ROSC had a greater increase from the initial rSO2 value than those without ROSC (16% vs. 10%). The mean rSO2 value during resuscitation was greater in patients with ROSC as compared to those without ROSC (39% vs. 31%).

The conclusion states, “During prehospital advanced life support, higher increases in rSO2 are observed in patients attaining ROSC, even before ROSC was clinically determined. Our findings suggest that rSO2 could be used in the future to guide patient-tailored treatment during cardiac arrest and could therefore be a surrogate marker of the systemic oxygenation state of the patient.”

DOC WESLEY COMMENTS

Despite the ever-increasing amount of research into cardiac arrest resuscitation, one thing remains clear: The primary goal is to save the life of the patient with the least amount of resulting neurological injury. To simply restart the heart isn’t enough. So, how can we determine which patients will have the best neurological outcome? At this point we just don’t know. But it seems intuitive that if the brain is adequately oxygenated then the patient will have a more favorable outcome.

In EMS, we only have control over the care we render.

This study looked only at ROSC as it didn’t have enough patients to determine whether rSO2 correlated with neurological outcome. In EMS, we only have control over the care we render, so it’s reasonable to examine the potential this technology could have in our hands. This study determined that no single rSO2 value was predictive, but instead it was the relative rise in the value during resuscitation as well the percent of time the rSO2 exceeded 30%. This is a start and is clearly better than end-tidal carbon dioxide (EtCO2) measurement, which can be falsely elevated with high-performance CPR.

The ability to actually monitor the oxygenation of the brain as an indicator of cerebral perfusion is enticing. However, we have only scratched the surface of this new technology and each published paper raises more questions than it answers. For example, in this study, the researchers state that the European (American Heart Association equivalent) 2010 guidelines were used. However, there was no data collected on the quality of CPR or the adherence to the guidelines as it relates to medication administration. To determine the ultimate value of this technology will require a large multicenter trial where every component of the resuscitation is controlled as tightly as possible.

Until then, I look forward to each published paper on this topic.

MEDIC WESLEY COMMENTS
I would risk saying that I get a little more excited about new science in EMS than the average Joe. And while I find the study interesting, I don’t believe it has application for prehospital practice at this time.

This technology may wind up only being used as a possible predictor of ROSC. It may prove valuable in assessing our current practice through future studies that address cerebral perfusion, but for now, it has no value in enhancing the care we provide in the streets.

The only thing that will make a difference in our cardiac arrest patients is what we already know—early detection, quality CPR, early defibrillation and ALS. Even with some of the current predictors that are available to us through our cardiac monitoring devices and EtCO2, we don’t alter the care we provide to our patients. We just give it all we have until it appears futile or medical control has given us permission to cease our efforts.

So, like Doc, I look forward to seeing other applications of this device in bettering the care we provide to our patients.