Too Much Oxygen and ICU Mortality
October 7, 2019
Written by Clay Smith
Hyperoxemia was associated with increased odds of ICU mortality but lacked a dose-response. This is more evidence that favors targeting SpO2 targets around 97% instead of 100%.
Why does this matter?
The Oxygen-ICU RCT found that patients with conservative SpO2 targets had lower mortality than those with higher SpO2 targets. Here is more evidence that too much oxygen is not a good thing.
Oxygen – can’t live without it…can’t live with too much
This was a large, multi-center, retrospective study of 5 ICUs in the UK, including 19,515 people. They found an association with increased ICU mortality in patients exposed to hyperoxemia. But they did not find a dose-response. The strength of this study was that it incorporated a time-weighted mean exposure. “Hyperoxemia dose was defined as the area under the PaO2-time curve above a threshold PaO2 value of 13.3 kPa (100 mmHg) divided by the number of hours of potential exposure.” Patients were grouped into subsets by time in the ICU. Cumulative hyperoxemia increased with longer total ICU stay. They found that for each of those time frames, there was an increased odds of ICU mortality. See Table.
As mentioned, they did not find a dose-response, i.e. greater absolute hyperoxemia associated with greater odds of mortality, which prompted them to call for additional prospective trials. In the meantime, I’ll continue to target lower SpO2 numbers, with a max of around 94%-97% to make sure I don’t overshoot.
The Association Between Supra-Physiologic Arterial Oxygen Levels and Mortality in Critically Ill Patients: A Multi-Centre Observational Cohort Study. Am J Respir Crit Care Med. 2019 Sep 12. doi: 10.1164/rccm.201904-0849OC. [Epub ahead of print]
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Reviewed by Thomas Davis