Supplemental oxygen does not reduce mortality in stroke patients

1. This randomized clinical trial showed that among patients with acute stroke, supplementary low-dose oxygen for 72 hours (either nocturnal or continuous) did not reduce death or disability at 3 months compared to control.

2. There were no significant differences in adverse events between treatment groups.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Hypoxia is common during the first few days after an acute stroke and is associated with high rates of neurological deterioration and death. There is evidence showing that continuous monitoring of oxygen saturation post-stroke is associated with better outcomes, but hypoxia is not always identified and treated despite rigorous monitoring. Supplemental oxygen could prevent hypoxia and repercussions of hypoxic brain damage, but can also have adverse effects. The aim of the Stroke Oxygen Study is to determine whether low dose oxygen therapy during the first 3 days after an acute stroke can improve mortality and disability. This randomized control study found that the groups who received either continuous or nocturnal supplemental oxygen experienced no significant decreases in mortality or disability compared to the control group, who received no routine oxygen. There were also no significant differences in the proportion of adverse events reported between the three groups.

There are a few limitations to the study. Firstly, minor benefits from oxygen treatment may have been masked by poor adherence, which is difficult to achieve without a 1 to 1 nurse-to-patient ratio and within the intensive care setting. Secondly, the main outcome of this study was assessed by postal questionnaire and telephone interviews for postal non-responders – this method is now replaced with a more preferred method of remote multiple-rater video-recorded interviews or in-person interviews and examinations. Finally, perhaps low-dose oxygen supplementation may not have been sufficient to prevent severe desaturations. Overall, this study provides evidence suggesting among patients who have had an acute stroke, that routine supplemental oxygen for 72 hours post-event did not reduce death or disability at 3 months compared to patients who did not receive routine oxygen.

Click to read the study, published in JAMA

Relevant Reading: Monitoring after the acute stage of stroke: a prospective study.

In-Depth [randomized control study]: This randomized clinical trial studied adults with a clinical diagnosis of acute stroke within 1 day of hospital admission across 136 hospitals in the UK. Patients were randomized into the following groups: 1) supplemental oxygen continuously for 72 hours (continuous group) 2) nocturnal oxygen (nocturnal group) 3) no routine oxygen, with oxygen only provided when desaturation is identified (control). Patients in the continuous and nocturnal group were given 3L/min of oxygen via nasal prong if their saturations were below 92%, and 2L/min if they were above 92%. The primary endpoint was the report of death or disability via the modified Rankin Scale (mRS) three months post-stroke, either via postal questionnaire or telephone interview for non-responders. The study found that persons who received supplemental oxygen in both the continuous and nocturnal group did not experience decreased rates of death or disability at 3 months compared to the control group. There were also no significant differences in the proportion of reported adverse events between treatment groups and control..

Of 8003 persons who were included in the study, 2668 were randomized into the continuous group, 2667 into the nocturnal group, and 2668 into the control group. The number of patients that remained in the study at three months were 2576 in the continuous group, 2576 in the nocturnal group, and 2567 in the control group. The unadjusted mRS odds ratio for a better outcome (lower mRS) was 0.97 (95%CI, 0.89 to 1.05; p = 0.47) for combined oxygen (continuous and nocturnal) vs control, and 1.03 (95%CI, 0.93 to 1.13; p = 0.61) for continuous oxygen vs nocturnal oxygen. Neurological impairment at 1 week improved from baseline to the same degree in all 3 groups with median NIHSS scores of 2 (IQR, 1 to 6) by 1 week. Mortality was similar in the oxygen (both treatment groups combined) and control groups (HR, 0.97 [99%CI, 0.78 to 1.21]; p = 0.75), and for continuous oxygen vs nocturnal oxygen (HR, 1.15 [99%CI, 0.90 to 1.48]; p = 0.15).


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