Possibility of predicting neurological outcome using regional cerebral oxygen saturation (rSO2) after cardiac arrest

G Model

ARTICLE IN PRESS

RESUS 6005 1

Resuscitation xxx (2014) xxx–xxx

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Resuscitation journal homepage: www.elsevier.com/locate/resuscitation

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Letter to the Editor

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Possibility of predicting neurological outcome using regional cerebral oxygen saturation (rSO2 ) after cardiac arrest 3

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Sir, The J-POP Registry Investigators1 reported that the regional cerebral oxygen saturation (rSO2 ) recorded on hospital admission can predict a good neurological outcome after cardiac arrest. Many previous experimental studies have indicated that the electroencephalogram (EEG) changes to flat within a few minutes after cardiac arrest and then recovers following reperfusion, depending on the no-flow time of the brain. In the clinical setting, EEGs in post-cardiac arrest patients also revealed four patterns, including a extremely low voltage (flat) pattern changing to a continuous pattern, or an epileptic pattern.2 A higher rSO2 value may be observed even if the EEG pattern is flat in the early phase in post-cardiac arrest patients. If a longer no-flow time is required until reperfusion occurs, the outcome may be poor despite higher rSO2 . I agree that as the rSO2 value may affect the quality of chest compressions during cardiac arrest, a lower level of initial rSO2 would result in a poor outcome.1 However, an anoxic brain injury may not always cause an increase in intracranial pressure in the early hours after return of spontaneous circulation (ROSC). Therefore rSO2 value might indicate a higher value after ROSC due to the influence of blood pressure, even when the EEG is flat. I speculate that this may be the reason why higher levels of rSO2 were observed after ROSC in cardiac arrest, even if there is serious brain dysfunction following anoxic-ischemic brain injury. Scrupulous attention

is necessary when we assess the rSO2 level after ROSC. The J-POP Registry study included patients both before and after ROSC (pulse detected patients were included in the J-POP Registry study, n = 52). It ultimately concluded that an initial rSO2 on hospitalization is a predictor of a good neurological outcome. However, our view is that it is critical to evaluate rSO2 just after ROSC as the clinical significance of the rSO2 value is different before and after ROSC. Conflict of interest statement The author declares that there is no competing interest. References

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1. Ito N, Nishiyama K, Callaway CW, et al. for the J-POP Registry Investigators. Noninvasive regional cerebral oxygen saturation for neurological prognostication of patients with out-of-hospital cardiac arrest: a prospective multicenter observational study. Resuscitation http://dx.doi.org/10.1016/j.resuscitation.2014.02.012, pii: S03002014, 9572(14)00099-9. 2. Rundgren M, Rosén I, Friberg H. Amplitude-integrated EEG (aEEG) predicts outcome after cardiac arrest and induced hypothermia. Intensive Care Med 2006;32:836–42.

K. Kinoshita Q1 Division of Emergency and Critical Care Medicine, Q2 Department of Acute Medicine, Nihon University School of Medicine, Japan E-mail address: [email protected]

http://dx.doi.org/10.1016/j.resuscitation.2014.04.031 0300-9572/© 2014 Published by Elsevier Ireland Ltd.

Please cite this article in press as: Kinoshita K. Possibility of predicting neurological outcome using regional cerebral oxygen saturation (rSO2 ) after cardiac arrest. Resuscitation (2014), http://dx.doi.org/10.1016/j.resuscitation.2014.04.031

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