In the past we often routinely provided supplemental oxygen to patients who had suffered stroke or MI. But evidence began to appear that using oxygen in patients lacking evidence of hypoxemia might be of no benefit. Indeed, some evidence that hyperoxia might even be harmful began to appear (see our numerous columns on the potential dangers of oxygen listed at the end of todays column). The debate about use of oxygen in stroke and MI continued in the absence of randomized controlled trials.
Now, hopefully, the debate should end with the recent publication of results of randomized trials of oxygen in these two conditions.
First, the DETO2X-AMI trial was a registry-based randomized clinical trial using nationwide Swedish registries for patient enrollment and data collection (Hoffmann 2017). Patients with suspected myocardial infarction and an oxygen saturation of 90% or higher were randomly assigned to receive either supplemental oxygen (6 liters per minute for 6 to 12 hours, delivered through an open face mask) or ambient air. The study was open-label (that is, it was not double-blinded). Though hypoxemia developed more frequently in the ambient air group than the oxygen group (7.7% vs. 1.9%) there was no difference in the primary outcome of death from any cause within 1 year (5.0% and 5.1% in the oxygen and ambient air groups, respectively). Though more patients in the oxygen group were rehospitalized with MI within one year, this difference did not reach statistical significance. Results were consistent across all predefined subgroups. The authors conclude that routine use of supplemental oxygen in patients with suspected myocardial infarction who did not have hypoxemia was not found to reduce 1-year all-cause mortality.
Regarding stroke, the Stroke Oxygen Study (Roffe 2017) was a single-blind randomized clinical trial in the United Kingdom. Patients were enrolled within 24 hours of hospital admission if they had no clear indications for or contraindications to oxygen treatment. Participants were randomized 1:1:1 to continuous oxygen for 72 hours, nocturnal oxygen (21:00 to 07:00 hours) for 3 nights, or control (oxygen only if clinically indicated). Oxygen was given via nasal tubes at 3 L/min if baseline oxygen saturation was 93% or less and at 2 L/min if oxygen saturation was greater than 93%. The primary outcome was reported using the modified Rankin Scale score assessed at 90 days by postal questionnaire. The unadjusted odds ratio for a better outcome was 0.97 for oxygen vs control, and the odds ratio was 1.03 for continuous vs nocturnal oxygen (neither statistically significant). No subgroup could be identified that benefited from oxygen. The authors concluded that among nonhypoxic patients with acute stroke, the prophylactic use of low-dose oxygen supplementation did not reduce death or disability at 3 months. These findings do not support low-dose oxygen in this setting.
So we now have evidence from randomized trials that fail to show any benefit from routine use of oxygen in patients with MI or stroke who are not hypoxemic. Hopefully, the debate is now over.
Also timely is the recent publication of the updated British Thoracic Society Guideline for Oxygen Use in Adults in Healthcare and Emergency Settings (O'Driscoll 2017). We discussed the BTS guideline in our January 27, 2009 Patient Safety Tip of the Week Oxygen Therapy: Everything You Wanted to Know and More!. Many of the recommendations in the 2008 BTS guideline are unchanged but the scope of the guideline has been expanded to cover several new categories. The guideline continues to make the distinction in target oxygen saturation goals for most (9498%) and those at risk for hypercapnic respiratory failure (8892%).
Some of our prior columns on potential harmful effects of oxygen:
April 8, 2008 Oxygen as a Medication
January 27, 2009 Oxygen Therapy: Everything You Wanted to Know and More!
October 6, 2009 Oxygen Safety: More Lessons from the UK
July 2010 Cochrane Review: Oxygen in MI
December 6, 2011 Why You Need to Beware of Oxygen Therapy
February 2012 More Evidence of Harm from Oxygen
March 2014 Another Strike Against Hyperoxia
June 17, 2014 SO2S Confirms Routine O2 of No Benefit in Stroke
December 2014 Oxygen Should Be AVOIDed
August 11, 2015 New Oxygen Guidelines: Thoracic Society of Australia and NZ
Hofmann R, James SK, Jernberg T, et al. Oxygen Therapy in Suspected Acute Myocardial Infarction. NEJM 2017; published online first August 28, 2017
Roffe C, Nevatte T, Sim J, et al for the Stroke Oxygen Study Investigators and the Stroke Oxygen Study Collaborative Group. Effect of Routine Low-Dose Oxygen Supplementation on Death and Disability in Adults With Acute Stroke. The Stroke Oxygen Study Randomized Clinical Trial. JAMA 2017; 318(12): 1125-1135, September 26, 2017
O'Driscoll BR, Howard LS, Earis J, Mak V. British Thoracic Society Guideline for Oxygen Use in Adults in Healthcare and Emergency Settings. BMJ Open Respir Res 2017; 4(1)