What is the value of regional cerebral saturation in post-cardiac arrest patients? A prospective observational study

Background: The aim of this study was to elucidate the possible role of cerebral saturation monitoring in the post-cardiac arrest setting. Methods: Cerebral tissue saturation (SctO(2)) was measured in 107 successfully resuscitated out-of-hospital cardiac arrest patients for 48 hours between 2011 and 2015. All patients were treated with targeted temperature management, 24 hours at 33 degrees C and rewarming at 0.3 degrees C per hour. A threshold analysis was performed as well as a linear mixed models analysis for continuous SctO(2) data to compare the relation between SctO(2) and favorable (cerebral performance category (CPC) 1-2) and unfavorable outcome (CPC 3-4-5) at 180 days post-cardiac arrest in OHCA patients. Results: Of the 107 patients, 50 (47 %) had a favorable neurological outcome at 180 days post-cardiac arrest. Mean SctO(2) over 48 hours was 68 % +/- 4 in patients with a favorable outcome compared to 66 % +/- 5 for patients with an unfavorable outcome (p = 0.035). No reliable SctO(2) threshold was able to predict favorable neurological outcome. A significant different course of SctO(2) was observed, represented by a logarithmic and linear course of SctO(2) in patients with favorable outcome and unfavorable outcome, respectively (p < 0.001). During the rewarming phase, significant higher SctO(2) values were observed in patients with a favorable neurological outcome (p = 0.046). Conclusions: This study represents the largest post-resuscitation cohort evaluated using NIRS technology, including a sizeable cohort of balloon-assisted patients. Although a significant difference was observed in the overall course of SctO(2) between OHCA patients with a favorable and unfavorable outcome, the margin was too small to likely represent functional outcome differentiation based on SctO(2) alone. As such, these results given such methodology as performed in this study suggest that NIRS is insufficient by itself to serve in outcome prognostication, but there may remain benefit when incorporated into a multi-neuromonitoring bedside assessment algorithm.