Abstract

Objective: Uncertainty exists over the prognostic significance of low arterial oxygen saturation (SaO(2)) in acute stroke. We aimed to determine the strength of association of SaO(2) 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 SaO(2) level, as a continuous measure and as a cut-point for desaturation (SaO(2) 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 SaO(2) and death or dependency, with a nadir for optimal outcome at 96-97%. Patients with SaO(2) 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 SaO(2) outside of 96-97% is associated with poorer outcome after acute stroke. Clinical trial registration: HeadPoST is registered at ClinicalTrials.gov (NCT02162017).