Monday, May 08, 2017

What is the best oxygen target for critically ill patients?

Question Among critically ill patients, is a conservative oxygenation strategy aimed to maintain arterial saturation within physiologic limits more beneficial than a conventional strategy?

Findings In this randomized clinical trial that included 480 patients with an expected intensive care unit length of stay of 72 hours or longer, a conservative protocol for oxygen supplementation was associated with an absolute risk reduction for intensive care unit mortality of 8.6% compared with that for patients treated with conventional therapy. However, the trial was terminated early because of difficulty with patient enrollment.

Meaning Among critically ill intensive care unit patients with a length of stay of 72 hours or longer, a conservative protocol for oxygen therapy may be beneficial; however, because the trial was terminated early, these findings must be considered preliminary.

Importance Despite suggestions of potential harm from unnecessary oxygen therapy, critically ill patients spend substantial periods in a hyperoxemic state. A strategy of controlled arterial oxygenation is thus rational but has not been validated in clinical practice.

Objective To assess whether a conservative protocol for oxygen supplementation could improve outcomes in patients admitted to intensive care units (ICUs).

Design, Setting, and Patients Oxygen-ICU was a single-center, open-label, randomized clinical trial conducted from March 2010 to October 2012 that included all adults admitted with an expected length of stay of 72 hours or longer to the medical-surgical ICU of Modena University Hospital, Italy. The originally planned sample size was 660 patients, but the study was stopped early due to difficulties in enrollment after inclusion of 480 patients.

Interventions Patients were randomly assigned to receive oxygen therapy to maintain Pao2 between 70 and 100 mm Hg or arterial oxyhemoglobin saturation (Spo2) between 94% and 98% (conservative group) or, according to standard ICU practice, to allow Pao2 values up to 150 mm Hg or Spo2 values between 97% and 100% (conventional control group).

Main Outcomes and Measures The primary outcome was ICU mortality. Secondary outcomes included occurrence of new organ failure and infection 48 hours or more after ICU admission.

Results A total of 434 patients (median age, 64 years; 188 [43.3%] women) received conventional (n = 218) or conservative (n = 216) oxygen therapy and were included in the modified intent-to-treat analysis. Daily time-weighted Pao2 averages during the ICU stay were significantly higher (P greater than .001) in the conventional group (median Pao2, 102 mm Hg [interquartile range, 88-116]) vs the conservative group (median Pao2, 87 mm Hg [interquartile range, 79-97]). Twenty-five patients in the conservative oxygen therapy group (11.6%) and 44 in the conventional oxygen therapy group (20.2%) died during their ICU stay (absolute risk reduction [ARR], 0.086 [95% CI, 0.017-0.150]; relative risk [RR], 0.57 [95% CI, 0.37-0.90]; P = .01). Occurrences were lower in the conservative oxygen therapy group for new shock episode (ARR, 0.068 [95% CI, 0.020-0.120]; RR, 0.35 [95% CI, 0.16-0.75]; P = .006) or liver failure (ARR, 0.046 [95% CI, 0.008-0.088]; RR, 0.29 [95% CI, 0.10-0.82]; P = .02) and new bloodstream infection (ARR, 0.05 [95% CI, 0.00-0.09]; RR, 0.50 [95% CI, 0.25-0.998; P = .049).

Conclusions and Relevance Among critically ill patients with an ICU length of stay of 72 hours or longer, a conservative protocol for oxygen therapy vs conventional therapy resulted in lower ICU mortality. These preliminary findings were based on unplanned early termination of the trial, and a larger multicenter trial is needed to evaluate the potential benefit of this approach.

A nuanced discussion is provided in an accompanying editorial.

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