High vs. low oxygen levels during heart surgery: Is one strategy safer than the other?

Both high and low concentrations of oxygen can be safely administered to heart patients during cardiac surgery, according to a new analysis published in JAMA Surgery.[1] The two treatment strategies appear to have the same impact on kidney health.

“Ischemia reperfusion and oxidative injury are major contributors to postoperative organ injury, and oxygen is integral to these molecular processes,” wrote first author Marcos Lopez, MD, MS, associate professor with Vanderbilt University Medical Center (VUMC), and colleagues. “It is unclear, however, if increasing oxygen tension during surgery by the administration of oxygen in excess of that required to saturate hemoglobin (hyperoxia) attenuates or exacerbates perioperative organ injury. Hyperoxia increases oxygen content in tissues, may decrease regional hypoxia, and might limit poor clinical outcomes associated with perioperative ischemia. Conversely, hyperoxia may increase reactive oxygen species production, may exacerbate reperfusion injury and has been associated with postoperative organ injury.”

To learn more, Lopez et al. tracked data from 200 adult patients who underwent an elective cardiac surgery at the same high-volume medical center from 2016 to 2020. Patients were ineligible if pregnant, on using supplemental oxygen at home or presenting with carotid stenosis greater than 50% or a recent history of acute coronary syndrome. While hyperoxia was used for 100 patients, the other 100 were treated with normal blood oxygen levels (normoxia).

Overall, the group found that oxygen levels did not appear to impact the risk of kidney injury among heart patients. In fact, acute kidney injury occurred in the exact same number of patients—21—in both groups.