LOCO2 – Was Target SpO2 Too Low?

April 6, 2020

Written by Clay Smith

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A strategy targeting PaO2 55-70 mm Hg (SpO2 88-92%) vs PaO2 90-105 mm Hg (SpO2 ≥96%) appeared to increase mortality in patients with ARDS. From other sources, a reasonable target is SpO2 94-98%.

Why does this matter?
We know hyperoxia is bad: Oxygen-ICU; IOTA; ICU-ROX (null result); massive observational study lacking cool title in Chest; and yet another study with no snappy acrostic in Am J Respir Crit Care Med. We know hypoxia is also bad. What is the goldilocks SpO2 goal? Hint, I think the Chest study has the answer: 94-98%. Anyway, what did this loco study find?

It’s LOCO 2 go that low…
This was a multi-center RCT enrolling 205 patients with ARDS, with a “conservative” group targeting PaO2 55-70 mm Hg (SpO2 88-92%) and a “liberal” group targeting PaO2 90-105 mm Hg (SpO2 ≥96%). The study was stopped early by the data safety monitoring board because it appeared there was higher mortality in the conservative oxygen group. For the primary outcome of 28-day mortality, 34.3% had died in the conservative group vs 26.5% for the liberal group, a non-significant mortality increase of 7.8% (95%CI -4.8 to 20.6). At 90 days, mortality was 44.4% in the conservative group vs 30.4% in the liberal, for a mortality increase of 14.0% (95%CI 0.7 to 27.2). Five patients in the conservative group developed mesenteric ischemia. There was also possible signal that the conservative oxygen group may have more arrhythmia, atrial fibrillation, and other events leading to treatment, though this was not statistically significant. It seems we now know how low is too low. Just go with what Chest found and target 94-98%.

Source
Liberal or Conservative Oxygen Therapy for Acute Respiratory Distress Syndrome. N Engl J Med. 2020 Mar 12;382(11):999-1008. doi: 10.1056/NEJMoa1916431.

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