Abstract Body: Introduction
Elevated jugular bulb venous oxygen saturation (SjvO2) after cardiac arrest may occur because of diffusion-limited oxygen extraction secondary to perivascular edema. This edema may respond to treatment with hypertonic saline (HTS), thereby decreasing the barrier to oxygen diffusion. Alternatively, SjvO2 can rise when cerebral metabolic rate decreases, which is not affected by HTS. Electroencephalography (EEG) may differentiate between these etiologies and thus identify patients for whom treatment with HTS will improve oxygen extraction.

Hypothesis
Post-arrest patients with elevated SjvO2 would have improved oxygen extraction after treatment with HTS and qualitative EEG could be used to predict treatment responsiveness.

Methods
We conducted a retrospective multicenter cohort study including comatose survivors of cardiac arrest who had intermittent SjvO2 monitoring. We performed a Kruskal Wallis test comparing mean SjvO2 values within the first 24 hours after arrest between survivors and non-survivors. In the subgroup of patients who were treated with HTS for SjvO2 >75% and were EEG monitored, we quantified compared SjvO2 before and after HTS using a multivariable mixed-effects regression treating HTS as a fixed effect, adjusting for mean arterial pressure, partial pressure of arterial oxygen and partial pressure of carbon dioxide. We classified pre-treatment EEG patterns as benign or indicative of potential metabolic failure (generalized suppression, burst suppression, or discontinuous with superimposed rhythmic or periodic patterns) and tested for an interaction of EEG with HTS.

Results
We included 131 patients of whom 115 had SjvO2 data within 24 hours. Mean SjvO2 was higher (p = 0.0002) in non-survivors (77% [SD ±11]) than survivors (71% [SD ±11]). Twenty-one subjects received 28 HTS treatments. We found an independent association of HTS with decreased SjvO2 (ß = -3.8%; 95% CI, -6.4 to -1.2; p = 0.004). There was no interaction between pre-treatment EEG and HTS predicting SjvO2.

Conclusions
Early elevated SjvO2 is associated with mortality at hospital discharge. SjvO2 decreased following treatment with HTS, suggesting diffusion limited oxygen extraction secondary to modifiable perivascular edema. As mechanisms of secondary brain injury after cardiac arrest vary among patients, a precision approach to treatment is essential; however, we did not identify evidence to support the use of qualitative EEG to guide patient selection for treatment.