Trajectories of jugular bulb venous oxygen saturation after cardiac arrest are associated with distinct patterns of cerebral pathophysiology

Jugular bulb venous oxygen saturation (SjvO 2 ) reflects the balance between cerebral oxygen supply and consumption. Clinically distinct phenotypes of hypoxic ischemic brain injury (HIBI) may have different trajectories of SjvO 2 over time. We aimed to identify trajectories of SjvO 2 over time and explore the relationship between SjvO 2 and potential physiological confounders. We conducted a single center retrospective study including comatose survivors of cardiac arrest who underwent SjvO 2 monitoring. We used group-based trajectory modeling to identify distinct trajectories of SjvO 2 . We assessed the association between trajectory group and time-varying covariates, mean arterial pressure (MAP) and the partial pressures of oxygen (PaO 2 ) and carbon dioxide (PaCO 2 ) as time-varying covariates. Among 109 patients, we identified two SjvO 2 trajectories. Trajectory Group 1 comprised 57% of the population and had normal SjvO 2 that increased modestly over time. Group 2 comprised 43% of the population and was characterized by persistent pathologically elevated SjvO 2 . Increasing PaO 2 , PaCO 2 , and MAP were all associated with trajectory shape in Group 1, while PaO 2 and MAP, but not PaCO 2 were associated with Group 2 SjvO 2 trajectory. Trajectory Group 2 had evidence of more severe neurologic injury at presentation and worse outcomes. We identified two distinct trajectories of SjvO 2 after cardiac arrest. We found evidence of heterogeneity in the pathophysiology of HIBI between groups, suggesting distinct phenotypes of HIBI.