Posted on 12/01/2022 8:20:42 PM PST by ConservativeMind
Giving patients excess levels of oxygen during surgery is associated with a higher risk of subsequent kidney, heart, and lung injury, finds a large U.S. study.
Although the absolute risk remains low, this study suggests it is time to reconsider the liberal use of oxygen during general anesthesia, say experts in a linked editorial.
Oxygen is routinely given to almost all patients undergoing surgery with general anesthesia to help prevent hypoxia (dangerously low oxygen levels), and the World Health Organization recommends liberal use of oxygen to reduce the risk of infection.
During surgery, arterial blood hemoglobin oxygen saturation (SpO2) is continuously measured, enabling doctors to adjust the dose of oxygen to a target level. A normal SpO2 is 94-95%. Giving oxygen in excess of that required to saturate hemoglobin—known as supraphysiological oxygen—is common.
Supraphysiological oxygen can harm the body's cells and tissues, but the clinical relevance of these effects during surgery remain uncertain, and previous trials have not been able to detect any meaningful effects on organs.
After accounting for baseline factors and other potentially influential variables, increased oxygen exposure during surgery was associated with a higher risk of organ injury.
For example, patients at the upper end (75th percentile) of oxygen levels had 26% greater odds of acute kidney injury, 12% greater odds of myocardial injury, and 14% greater odds of lung injury compared with patients at the lower end (25th percentile).
Patients at the 75th percentile of oxygen levels also had 9% greater odds of stroke and 6% greater odds of 30 day mortality than patients at the 25th percentile.
However, patients at the 75th percentile had a slightly shorter length of stay compared with patients at the 25th percentile, an effect unchanged after excluding patients who died before discharge.
These are observational findings, so can't establish cause.
(Excerpt) Read more at medicalxpress.com ...
Is your point that the problem was with pure oxygen but not with concentrated oxygen?
Is concentrated oxygen like you get with hyperbaric oxygen therapy —safe?
Technically hyperbaric can be low inspired content. Using pressure drives it to tissue level instead of hemoglobin delivered. Hyperbaric for wound actually counts on free radicals to sterilize the wound.
The injury from superoxide tx takes days to develop. Although damage can be chemically measured in 12 hours or so actual fibrosis and clinically significant fibrosis takes a week or so.
When I give a general anesthetic there are reasons to bump the inspired fraction a little. Room air is 21% oxygen. I usually run patients around 30% all things being equal. But 60% is the real line you only cross if you have to
As well, I have met Nurses who believe that a CO2 Retainer should not be provided supplemental Oxygen. Such completely misunderstand the problem. I knew one Nurse who constantly dropped the FIO2 once she heard ‘retainer.’ She killed one Patient after I left for the day. That one was terminal, but dying of Oxygen starvation was not right. She was too stupid to reason with. She accelerated that expiration only slightly, but I watched her ever after until I left or she was terminated.
I don't know what people think Hyperbaric is, but probably they ought not discuss it from absolute ignorance.
IIRC, excess O2 can dry out the coating on avoili, a fatty substance called the pulmonary surfacant that keeps avioli from collapsing. (also dried out by smoking)
related, from 2016:
Too Much Oxygen: Hyperoxia and Oxygen Management in Mechanically Ventilated Patients
https://pubmed.ncbi.nlm.nih.gov/26820270/
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