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Impact of Restrictive Versus Liberal Oxygenation on Pulmonary Decline After Cardiac Surgery: A Substudy of the
Astrid Duus Mikkelsen1, Sebastian Wiberg2, Hans Henrik Lawaetz Schultz3
1Department of Cardiology, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
Objectives:
Pulmonary dysfunction is a known complication of cardiac surgery. High fractions of inspired oxygen (FiO2) during the critical pulmonary reperfusion phase of cardiopulmonary bypass (CPB) weaning is a proposed pathophysiological contributor yet remains sparsely investigated.
Design:
Predefined, exploratory substudy of the GLORIOUS randomized, clinical trial.
Setting:
Single tertiary center with cardiothoracic surgery expertise.
Participants:
Adult patients undergoing nonemergent coronary artery bypass grafting (CABG) and/or surgical aortic valve replacement.
Interventions:
Restrictive (FiO2 50%) versus liberal (FiO2 100%) oxygenation during CPB and the first hour after weaning or until patient transfer from the operating table. Pulmonary function (forced expired volume in 1 second [FEV₁], forced vital capacity [FVC], FEV₁/FVC, and diffusion capacity of carbon monoxide) was measured preoperatively and 3 months postoperatively.
Measurements And Main Results:
A total of 878 patients were included in the study. Postoperatively, at the 3-month mark, pulmonary function declined across all parameters in the overall study population (median FEV₁ [% predicted] by 8.3 percentage points [95% CI 6.6 to 8.3], FVC [% predicted] by 6.1 percentage points [95% CI 5.2 to 7.0], FEV₁/FVC by 1.6 percentage points [95% CI 1.0 to 2.1], and diffusion capacity of carbon monoxide [% predicted corrected] by 7.7 percentage points [95% CI 6.2 to 9.1], all p< 0.001). However, no significant between-group differences in decline were observed (all p > 0.3), including in subgroup analyses.
Conclusions:
While pulmonary function exhibited a mild-to-moderate decline 3 months after cardiac surgery, a restrictive (FiO2 50%) oxygenation strategy during CPB did not attenuate this decline compared with a liberal (FiO2 100%) strategy. Findings are hypothesis-generating.
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