Abstract 218: Using Regional Cerebral Oxygen Saturation Measurements to Study When to Deliver Shocks During CPR: Can Optimal Timing Be Determined?

According to the present guidelines of cardiopulmonary resuscitation, the cardiac arrest algorithm suggests shocks be delivered soon after recognizing ventricular fibrillations (VF). In our study, we investigated the possibility that optimal timing to deliver shocks may exist and may be predicted by regional cerebral oxygen saturation measurements. Methods: From the onset of contact with cardiac arrest patients, the tissue oxygenation index (TOI) was continuously monitored (NIRO-200NX, Hamamatsu Photonics). In 19 patients who were delivered shocks following VF, we investigated the following parameters with respect to whether or not the return of spontaneous circulation (ROSC) was achieved: TOI value just before shocks during interruptions in chest compressions, (pre-shock TOI); TOI value during shocks (in-shock TOI); and the amount of decrease in TOI during interruption in chest compressions (ΔTOI). Results: The total number of shocks delivered was 37. In all of the shocks, the pre-shock TOI, the in-shock TOI and ΔTOI were 41.4±9.1%, 38.1±8.7% and -3.5±2.6%, respectively. In 5 shocks that resulted in ROSC, the in-shock TOI was 51.6±4.2%, and for 32 shocks that did not result in ROSC, the in-shock TOI was 36.6±7.7%. Conclusion: Values of the in-shock TOI measurements followed by ROSC were significantly higher than those that did not result in ROSC, and this outcome suggests shocks with low in-shock TOI readings may not achieve ROSC. Considering that TOI decreases when chest compressions are interrupted in preparation for the administration of shocks, better results may be achieved if the algorithm is adjusted to deliver shocks after TOI has reached a higher value.