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How much oxygen is too much?

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Coffee Brown and I recently recorded a podcast on that most necessary molecule for mammalian life – O2. The question we consider: should medics send patients to hospital with 100% oxygen? Should all patients get supplemental oxygen in the hospital?

The answer: an emphatic no!

First author Derek Chu and Paul Young and colleagues recently conducted a meta-analysis published in the journal The Lancet. They examined whether less or more oxygen given in hospital was associated with better or worse outcomes.

Here is an excerpt from the abstract.

25 randomised controlled trials enrolled 16 037 patients with sepsis, critical illness, stroke, trauma, myocardial infarction, or cardiac arrest, and patients who had emergency surgery. Compared with a conservative oxygen strategy, a liberal oxygen strategy (median baseline saturation of peripheral oxygen [SpO2] across trials, 96% [range 94–99%, IQR 96–98]) increased mortality in-hospital (relative risk [RR] 1·21, 95% CI 1·03–1·43, I2=0%, high quality), at 30 days (RR 1·14, 95% CI 1·01–1·29, I2=0%, high quality), and at longest follow-up (RR 1·10, 95% CI 1·00–1·20, I2=0%, high quality). Morbidity outcomes were similar between groups. Findings were robust to trial sequential, subgroup, and sensitivity analyses.

The bottom line: higher levels of oxygen were associated with more death. A link to the whole article at Lancet is here:

IOTAYou can read about the IOTA study here.

You can read about The Avoid trial here.

Chip Gresham’s 2012 The Sharp End article describes the The 1950s JAMA paper referenced in the podcast. Here is an excerpt:

Like giving fluid to hypotensive patients, giving oxygen to every ill- looking ED patient is a traditional practice that has proven difficult to break. Not surprisingly, the evidence for using oxygen for most ED situations is very weak.

While most people would agree that using oxygen for a minor viral illness or a fractured ankle is unlikely to help, the “basic science” rationale for treating myocardial ischemia with inhaled oxygen in order to improve the myocardial tissue oxygenation is more plausible. However, despite giving oxygen for angina for over 100 years, and the widespread recommendations for its use for “cardiac” chest pain over the last 60 years, they are many physiologic and patient-based reasons to suspect it may be doing more harm than good.

In 1950, JAMA published an article titled One hundred percent oxygen in the treatment of acute myocardial infarction and severe angina pectoris that showed 100% oxygen caused increased and longer duration ECG findings of ischemia. Since then, there have been multiple studies that show the potentially detrimental physiological effects of high flow oxygen, but there have been few large patient-oriented trials that show benefit of supplemental oxygen. The Cochrane Review published a systemic review in 2010 titled Oxygen therapy for acute myocardial infaction that concluded “There is no conclusive evidence from randomized controlled trials to support the routine use of inhaled oxygen in patients with acute AMI.” The accompanying editorial, titled Oxygen therapy in acute myocardial Infarction- too much of a good thing? clearly opines that we are likely killing patients with our indiscriminate use of oxygen.”

Categories: Uncategorized

Joe Alcock

Emergency Physician, Educator, Researcher, interested in the microbiome, evolution, and medicine

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