Exposure to hyperoxia in the immediate post-intubation period after admission to the emergency department (ED) is associated with worse outcomes in mechanically ventilated patients, according to researchers.
“We found that the unnecessary administration of excessive amounts of oxygen and resultant elevated levels of oxygen in the bloodstream were very common in the emergency department,” said Brian M. Fuller, MD, MSCI, an associate professor of anesthesiology and emergency medicine at Washington University in St. Louis, and the lead author.
“This early hyperoxia in the emergency department was associated with an increased risk of death, longer mechanical ventilation duration and lengths of stay,” said Dr. Fuller, who suggested that normoxia should be targeted immediately after the initiation of mechanical ventilation.
Although relatively prolonged hyperoxia exposure is associated with worse outcomes, the researchers wanted to study the effects of hyperoxia for ventilated patients in the ED. Were these comparatively brief exposures long enough to do harm?
“The objectives of this study were to assess the association between hyperoxia after intubation in the ED, and clinical outcomes in patients who were subsequently normoxic while in the ICU,” the researchers wrote. “We hypothesized that ED hyperoxia would be associated with increased hospital mortality and lengths of stay.”
In this observational cohort study, which was presented at the 2018 annual congress of the Society of Critical Care Medicine (abstract 20), researchers divided patients into three oxygen exposure groups based on their partial pressure of oxygen (PaO2) values obtained while mechanically ventilated in the ED: hypoxia at PaO2 less than 60 mm Hg; normoxia at PaO2 of 60 to 120 mm Hg; and hyperoxia at PaO2 greater than 120 mm Hg.
They looked at 688 mechanically ventilated normoxic ICU patients who had mechanical ventilation initiated in the ED.
They found that ED normoxia occurred in 350 (50.9%) patients, whereas 300 (43.6%) had exposure to ED hyperoxia. The researchers said the ED hyperoxia group had a median ED PaO2 of 189 mm Hg (146-249 mm Hg), compared with an ED PaO2 of 88 mm Hg (76-101 mm Hg) in the normoxia group (P<0.001).
More patients in the ED hyperoxia group died (29.7%) than in the normoxia (19.4%) group, according to the results. The researchers said ED hyperoxia was an independent predictor of hospital mortality (adjusted odds ratio, 1.95; 95% CI, 1.34-2.85).
Additionally, compared with the normoxia group, the hyperoxia group saw a decrease in ventilator-, ICU- and hospital-free days, which were associated with experiencing hyperoxia in the ED (P<0.001 for all). “The primary outcome was hospital mortality,” the researchers noted. “A backward, stepwise, multivariable logistic regression model evaluated mortality as a function of oxygen exposure group.”
“This is an incredibly important study with significant impact on the management of mechanically ventilated patients in the ED,” said William A. Knight IV, MD, an associate professor of emergency medicine and neurosurgery at the University of Cincinnati College of Medicine, who was not associated with the study.
“Dr. Fuller’s team had two very important conclusions for emergency physicians,” Dr. Knight said. “The first is that exposure to hyperoxia from mechanical ventilation is common, and the second is that there is an association with worse outcome (to include mortality) with hyperoxia. The fact that Dr. Fuller’s team has identified the prevalence of hyperoxia, as well as the association with worsened outcomes, represents a simple intervention for emergency physicians to consider.”
Dr. Fuller said that although it has been known for some time that hyperoxia worsens outcomes, it is probably tolerated in EDs because the primary focus has been in avoiding hypoxia and its known complications. Another possible reason, he said, was “prior to our study, it had not been demonstrated that an isolated period of hyperoxia in the emergency department may be harmful.”
Even relatively brief periods of hyperoxia can be harmful for critically ill patients, Dr. Fuller said. “The time spent in the emergency department, similar to the operating room, is on the scale of hours, so these results could apply to critically ill patients in the operating room as well.”
Dr. Fuller said, “There is no downside to targeting normoxia, so given the association between hyperoxia and harm, excessive oxygen administration should be avoided.” Correcting the problem of hyperoxia would be a simple matter of “just turning a dial on the ventilator,” he said.
Dr. Knight agreed. “My take-home message for clinicians is that there is no reason to not target normoxia in this patient population, especially when one considers the preponderance of associated literature that has been previously published regarding the dangers of hyperoxia in post–cardiac arrest patients, neurologically injured patients, patients with lung injury and others.”