Thread by @gbosslet

THREAD
Recently in our #MICU, I took pics of the oxygen sats of patients on oxygen supplementation.

What is the optimal oxygen supplementation strategy for a clinically stable patient in the ICU?

Follow me down this #tweetorial rabbit hole. #medtwitter #pulmcc #AIMW19
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Given that population health improvements often come from small benefits in large populations, and the fact that #oxygen is one of the most commonly prescribed interventions in the #ICU, there is potential for benefit if we can correctly titrate our oxygen titration.
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I’m going to refer to hypoxia and hyperoxia in this #medthread, and I’d like to (somewhat arbitrarily) define these terms. I’ll call hypoxia anything below 90% and hyperoxia anything above 96%. This is based upon some of the literature I will discuss.
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If one remembers the oxygen-hemoglobin dissociation curve, this below 90% correlates approx. with a PaO2 of 60 mmHg. A sat of 96% correlates to a PaO2 of approx. 85 mmHg. #PMID 28507176
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I’m going to suggest that targeting a saturation above 97% may be harmful- this is not a unique opinion. @pulmcrit did a nice discussion of this here emcrit.org/pulmcrit/icu-o…. I’m going to try and expand a bit on that blog post to group the relevant data.
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There are a couple of mechanisms by which targeting higher sats could cause harm in ICU populations: increased LOS on the vent, and oxidative damage to the tissues. Credit @pulmcrit for this graphic.
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And some physiologic data suggests that targeting a higher delivered oxygen may actually reduce oxygen consumption. In 20 critically ill patients who were maintained on 40% FiO2, this study increased their FIO2 to 100% for 1 hour and observed VO2 effects. #PMID 1995227
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So we have theoretical and physiologic data that provision of #oxygen when it is not needed may not be helpful and may actually be detrimental. Do we have any evidence from the real world that this is the case?
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The AVOID study (PMID 26002889) and the DETO2X-SWEDEHEART (PMID 28844200) study both evaluated provision of oxygen to normoxic #STEMI patients and both demonstrated no benefit (Goodbye to the “O” in MONA!).
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Oxygen to normoxic #stroke patients did not change mortality or neurologic outcome in the SOS-RCT study (PMID 28973619).
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And provision of supratherapeutic oxygen during surgery does not reduce surgical site infections in a study from 2009 (PMID 19826023); although the WHO still recommends 80% FiO2 supplementation during surgery for this specific reason (2017 PMID 27816414).
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So the data in patients who are normoxic seems to abandon the dogmatic reflex to provide oxygen in order to help improve outcomes… which jettisons some long-held therapeutic beliefs.
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I hear the cynics now: Great, Gabe. You’ve proven giving #oxygen to non-critically ill patients who aren’t hypoxic is not beneficial. But our patients are very sick and need oxygen!!!
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Epidemiologic studies suggest that hyperoxia in the first 24 hours of ICU admission may be associated with increased mortality- the “sweet spot” PaO2 appears to be around 120-150 mmHg. (PMID 19077208)
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And these data are mirrored almost exactly by a similar study performed in a pediatric ICU population. Same sweet spot!
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And hyperoxia in the Emergency Room is associated with worse outcomes- these are retrospective data from a single center, but the dose relationship is quite compelling- PMID 29347982
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AND hyperoxia after cardiac arrest appears to be an independent predictor of outcome, bested only by PEA/asystole as the initial rhythm!! PMID 20516417
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So, where are we? It appears that provision of oxygen to normoxic patients has not been demonstrated to improve any measurable outcomes AND provision of TOO MUCH oxygen to the critically ill may be detrimental. Seems like this is ripe for an #RCT…
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The Oxygen-ICU RCT (PMID 27706466) randomized 434 patients to conventional (97%-100%) versus conservative (94%-98%) oxygen strategies and demonstrated a considerable mortality improvement in the conservative oxygen group.
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The Oxygen-ICU study was a single site study halted early due to an earthquake, so the results should be interpreted with caution. When combined with the other data I presented in this #tweetorial, it seems reasonable that a more conservative oxygen strategy is sensible.
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AND the ICU-ROX study by @dogICUma, a multi-site study in Australia and New Zealand will randomize 1000 patients to a conventional arm and an intervention arm (sats 90%-96%) and should be published soon (last patient recruited May 2018). Look forward to those data!
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So to sum up:

•Hyperoxia has little role in the treatment of normoxic patients with non-ICU pathology
•Hyperoxia appears to be detrimental in well-done retrospective studies of ICU patients (we will have a more robust RCT on this soon)
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Therefore, the following seem reasonable to improve oxygen management in the ICU:
1. Change ventilator wean parameters to a lower AND upper value
2. Set (silent) upper range limits on alarms on ICU monitors, and
3. Empower RTs to reduce FiO2 to as low as 21% on the vent
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FIN