NEJM Journal Watch
Patricia Kritek, MD, reviewing
Two trials showed no benefit to targeted titration of oxygen in the intensive care unit.
Assuring adequate oxygen delivery is a central tenet in the intensive care unit (ICU); however, some studies have suggested harm from tissue hyperoxia. In two recent trials, researchers attempted to determine the best target for oxygenation in critically ill patients.
In a trial from Vanderbilt, 2500 patients who were receiving mechanical ventilation were randomized to peripheral oxygen saturation (SpO2) targets that were high (96%–100%), intermediate (92%–96%), or low (88%–92%). Every 2 months during the 3-year study, the target value was changed for all patients cared for in the medical ICU and emergency department. Protocolized adjustments to reach the target SpO2 were limited to fraction of inspired oxygen (FiO2; i.e., not other ventilator settings). About 20% of patients were in shock, and 13% of patients had experienced cardiac arrest. The median oxygen saturation values in the groups were 94%, 95%, and 97% (low to high), whereas median FiO2 values were 0.31, 0.37, and 0.45, respectively. At day 28, mortality and number of ventilator-free days were similar for all oxygenation targets.
In another trial, Australian investigators randomized 425 patients with cardiac arrest and return of spontaneous circulation (ROSC) outside of the hospital to low (90%–94%) or high (98%–100%) goals. Titration began when paramedics first achieved ROSC and continued until the patient arrived in the ICU. The trial was stopped early due to logistical challenges caused by the COVID-19 pandemic. Nearly all patients were intubated in the field, and median FiO2 values in the emergency department were 0.5 and 0.8. Survival to hospital discharge, the primary outcome, was 38% in the low-target group and 48% in the high-target group — a difference of borderline significance (P=0.05). Hypoxic events were significantly more common in the low-target group (31% vs. 16%). Other secondary outcomes were not significantly different in the two groups.
CITATIONS
Bernard SA et al. Effect of lower vs higher oxygen saturation targets on survival to hospital discharge among patients resuscitated after out-of-hospital cardiac arrest: The EXACT randomized clinical trial. JAMA 2022 Nov 8; 328:1818. (https://doi.org/10.1001/jama.2022.17701)
Semler MW et al. Oxygen-saturation targets for critically ill adults receiving mechanical ventilation. N Engl J Med 2022 Nov 10; 387:1759.
COMMENT
Despite concern about tissue hyperoxia based on animal studies, no convincing evidence shows that lower oxygenation targets improve outcomes. In fact, several outcomes in the Australian study suggests harm with this approach. Maintaining higher oxygen targets in the prehospital setting makes sense. Once patients are in the ICU, we should turn down the oxygen so that SpO2 is less than 100%; however, targeting narrow ranges below 100% has no substantial effect on patient outcome.