Early Arterial Oxygen Tension Thresholds for Mechanically Ventilated Patients with Non-traumatic Acute Brain Injury: A Bayesian Analysis of Three Large Neurocritical Care Datasets

Abstract Purpose Optimal arterial oxygen tension (PaO 2 ) thresholds in mechanically ventilated patients with nontraumatic acute brain injury (ABI), defined as intracerebral hemorrhage (ICH), aneurysmal subarachnoid hemorrhage (SAH), and acute ischemic stroke (AIS), remain uncertain. We aimed to identify ABI-specific early PaO 2 thresholds associated with lowest intensive care unit (ICU) mortality in mechanically ventilated ICU patients and compare these with guideline recommendations. Methods This retrospective multicenter cohort study utilized the Australian and New Zealand Intensive Care Society Adult Patient Dataset (ANZICS-APD; N = 11,264). Bayesian logistic regression was performed with day 1 PaO 2 as the independent variable and ICU mortality as the dependent variable. Priors were derived from the Medical Information Mart for Intensive Care-IV (MIMIC-IV; N = 1789) and Extubation in Neurocritical care Observational Study (ENIO; N = 544) datasets. Day 1 PaO 2 thresholds were identified by calculating the range of values within 4% of the minimum mortality. The risk of ICU mortality across these PaO 2 groups was compared with the European Society of Intensive Care Medicine (ESICM) recommendations. Results Of the 11,264 patients in the ANZICS-APD suitable for analysis, 4846 had ICH, 4319 had aneurysmal SAH, and 2099 had AIS. Across all ABI types, day 1 PaO 2 > 299 mm Hg was rare (< 10%), with remaining patients distributed equally across the < 80, 80–120, and 120–299 mm Hg categories. The association between day 1 PaO 2 and ICU mortality differed by ABI subtype: SAH showed a more pronounced U-shaped relationship than ICH and AIS. PaO 2 thresholds that minimized ICU mortality (ICH: 80–230 mm Hg; SAH: 100–190 mm Hg; AIS: 100–160 mm Hg) were broader than current ESICM (PaO 2 between 80 and 120 mm Hg) guideline recommendations yet conferred equivalent risk of ICU mortality. Extreme hyperoxia (> 299 mm Hg) was associated with increased risk of ICU mortality across all ABI subtypes [P(OR > 1) = 84–99%]. Conclusions In mechanically ventilated patients with nontraumatic ABI, we defined generalizable early PaO 2 thresholds that were broader than current recommendations while conferring equivalent ICU mortality risk. PaO 2 exposure beyond these ranges may be harmful.