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).