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 the liberal use of oxygen to reduce the risk of infection.
But in a new study, scientists found giving patients excess levels of oxygen during surgery is associated with a higher risk of subsequent kidney, heart, and lung injury.
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.
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.
In the study, researchers examined whether supraphysiological oxygen administration during surgery is associated with lower or higher postoperative kidney, heart, and lung injury.
They used data from over 350,000 patients undergoing surgery with general anesthesia and endotracheal intubation (a breathing tube placed into the windpipe) at 42 medical centers across the United States between January 2016 and November 2018.
Background information on factors such as age, sex, race, weight (BMI), and medical history was collected, and patients were screened for kidney, heart, and lung injury before and after their surgery.
The researchers then used an algorithm to calculate the amount of oxygen given above the air level (21%) against the time spent with oxygen saturation at or above 92% throughout the surgery.
Medical records were used to track cases of acute kidney, myocardial, and lung injury as well as 30-day mortality, hospital length of stay, and stroke.
The average duration of surgery was 205 minutes. Acute kidney injury was diagnosed in 6.5% of patients, myocardial injury in 2.8%, and lung injury in 4.4%.
The team found that 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.
This study and previous research show that oxygen can be a double-edged sword.
The team says a large clinical trial to detect small but clinically significant effects on organ injury and patient cantered outcomes is needed to guide oxygen administration during surgery.
If you care about lung health, please read studies about the cause of wheezing in the lungs, and she was being treated for her lungs, but the problem was her heart.
For more information about health, please see recent studies about mouthwashes that may suppress the COVID-19 virus, and results showing rare blood clots after COVID-19 vaccination.
The study was conducted by David R McIlroy et al and published in The BMJ.
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