Oxygen: NIRS and dear to our heart… and brain

Prediction of return of spontaneous circulation during cardiopulmonary resuscitation by pulse-wave cerebral tissue oxygen saturation: a retrospective observational study

Background

It is difficult to predict the return of spontaneous circulation (ROSC) during cardiopulmonary resuscitation (CPR). Cerebral tissue oxygen saturation during CPR, as measured by near-infrared spectroscopy (NIRS), is anticipated to predict ROSC. General markers of cerebral tissue oxygen saturation, such as the tissue oxygenation index (TOI), mainly reflect venous oxygenation, whereas pulse-wave cerebral tissue oxygen saturation (SnO₂), which represents hemoglobin oxygenation in the pulse wave within the cerebral tissue, is an index of arterial and venous oxygenation. Thus, SnO₂ may reflect arterial oxygenation to a greater degree than does TOI. Therefore, we conducted this study to verify our hypothesis that SnO₂ measured during CPR can predict ROSC.

Methods

Cardiac arrest patients who presented at the Emergency Department of Yamagata University Hospital in Japan were included in this retrospective, observational study. SnO₂ and TOI were simultaneously measured at the patient’s forehead using an NIRS tissue oxygenation monitor (NIRO 200-NX; Hamamatsu Photonics, Japan). We recorded the initial, mean, and maximum values during CPR. We plotted receiver operating characteristic curves and calculated the area under the curve (AUC) to predict ROSC.

Results

Forty-two patients were included. SnO₂ was significantly greater in the ROSC group than in the non-ROSC group in terms of the initial (37.5% vs 24.2%, p = 0.015), mean (44.6% vs 10.8%, p < 0.001), and maximum (79.7% vs 58.4%, p < 0.001) values. Although the initial TOI was not significantly different between the two groups, the mean (45.1% vs 36.8%, p = 0.018) and maximum (71.0% vs 46.3%, p = 0.001) TOIs were greater in the ROSC group than in the non-ROSC group. The AUC was 0.822 for the mean SnO₂ (95% confidence interval [CI]: 0.672–0.973; cut-off: 41.8%), 0.821 for the maximum SnO₂ (95% CI: 0.682–0.960; cut-off: 70.8%), and 0.809 for the maximum TOI (95% CI: 0.667–0.951; cut-off: 49.3%).

Conclusion

SnO₂ values measured during CPR, including immediately after arrival at the emergency department, were higher in the ROSC group than in the non-ROSC group.