Abstract 40: Optimal Cerebral Oxidation Levels for Brain Protection During Resuscitation in Cases of Refractory Cardiac Arrest

Abstract

Background: Some clinical studies suggest that exposure to hyperoxia after resuscitation from cardiac arrest might worsen anoxic brain injury. Objective: The aim of this study was to investigate the association between regional cerebral oxygen saturation (rSO2) levels measured immediately on hospital arrival and neurological outcome at hospital discharge in cardiac arrest on arrival (CAOA) patients after out-of-hospital cardiac arrest (OHCA) Methods: This study was a prospective cohort study. Of 418 OHCA patients, 186 consecutive non-traumatic, CAOA patients were prospectively registered from April 2009 to March 2011. The rSO2 levels were measured with sensors placed on either side of their forehead using a near-infrared spectroscopy device (INVOS, Covidien, US) within 3 minutes after hospital arrival. We monitored rSO2 levels at least for more than one minute and used the lower of the 2 measured rSO2 levels for analysis. Clinical staff performed ordinary post-cardiac-arrest interventions (PCAIs) regardless of rSO2 levels. We divided eligible patients into the four groups by 20%-rSO2 level stratum. The primary endpoint was good neurological outcome (Cerebral Performance Category; =<2) at hospital discharge according to the “Utstein-style” guideline and we compared neurological outcome among the groups. Results: Among 186 CAOA patients in the PCAIs era, 18 patients (9.7%) had good neurological outcome. However, none in the lowest level group (rSO2=<20%, n=109) had good neurological outcome at hospital discharge. Mortality after CAOA decreased with increasing rSO2 levels. However, rate of good neurological survivors hit a ceiling in the highest rSO2 group (rSO2>60%, n=12). Conclusion: This study suggests that one of the main goals of resuscitation might be to maintain rSO2 levels during resuscitation in cases of refractory cardiac arrest, however rSO2 levels might hit a ceiling for brain protection.