Oxygen desaturation and adverse outcomes in acute stroke: Secondary analysis of the HeadPoST study

Objective: Uncertainty exists over the prognostic significance of low arterial oxygen saturation (SaO₂) in acute stroke. We aimed to determine the strength of association of SaO₂ and adverse outcomes among participants of the international Head Positioning in acute Stroke Trial (HeadPoST). Methods: Post-hoc analyzes of HeadPoST, a pragmatic cluster-crossover randomized trial of lying flat versus sitting up head positioning in 11,093 patients (age ≥18 years) with acute stroke at 114 hospitals in 9 countries during 2015–2016. Associations of the lowest recorded SaO₂ level, as a continuous measure and as a cut-point for desaturation (SaO₂ <93%), in the first 24 h and clinical outcomes of death or dependency (modified Rankin scale [mRS] scores 3–6) and any serious adverse event (SAE) at 90 days, were assessed in generalized linear mixed models adjusted for baseline and in-hospital management confounders. Results: There was an inverse J-shaped association between SaO₂ and death or dependency, with a nadir for optimal outcome at 96–97%. Patients with SaO₂ desaturation were older, and had greater neurological impairment, premorbid disability and cardiorespiratory disease. Desaturation was not clearly associated with death or dependency (adjusted odds ratio [aOR] 1.19, 95% confidence interval [CI] 0.95–1.48) but was with SAEs (aOR 1.34, 95% CI 1.07–1.68), without heterogeneity by head position, cardiac-respiratory comorbidity, or other pre-specified subgroups. Conclusions: Any change in SaO₂ outside of 96–97% is associated with poorer outcome after acute stroke. Clinical trial registration: HeadPoST is registered at ClinicalTrials.gov (NCT02162017).