Oxygen extraction trajectories during cardiopulmonary bypass impact postoperative outcomes in coronary artery bypass grafting.

Abstract

Goal-directed perfusion strategies during cardiopulmonary bypass typically target indexed oxygen delivery thresholds to reduce acute kidney injury and other complications. This delivery-only paradigm may not fully reflect patient-specific metabolic demand. The oxygen extraction ratio integrates delivery and consumption and may better reflect perfusion adequacy. We tested the hypothesis that intraoperative oxygen extraction ratio is associated with postoperative outcomes. We retrospectively analyzed 885 adults who underwent isolated coronary artery bypass grafting (October 2021 to July 2025). Unsupervised clustering identified distinct extraction ratio trajectory phenotypes. Baseline, intraoperative, and postoperative variables were compared across phenotypes, and weighted logistic models assessed associations with Society of Thoracic Surgeons major morbidity or mortality and acute kidney injury. An exploratory subgroup analysis evaluated whether maintaining higher indexed oxygen delivery mitigated risk in patients with elevated extraction ratio. Three oxygen extraction ratio trajectories were identified: low (mean 21%), moderate (mean 23%), and high (mean (24.4%). Patients with high extraction ratio had more anemia, diabetes, and heart failure and lower average oxygen delivery. After adjustment for baseline risk, high extraction ratio was associated with greater morbidity and mortality (odds ratio, 2.04 [1.5-2.8], P < .001) and acute kidney injury (odds ratio, 1.6 [1.2-2.1], P < .001). In the high extraction ratio group, maintaining an indexed oxygen 300 mL/min/m² or greater for 92% or more of cardiopulmonary bypass time would have relatively reduced the incidence of acute kidney injury (relative risk reduction, 66.8%; 13.9-97.9) and morbidity and mortality (63.8%; 15.2-96.8). Elevated oxygen extraction ratio was independently associated with postoperative morbidity and acute kidney injury. Incorporating extraction ratio into goal-directed perfusion frameworks may enable a more individualized, physiology-guided perfusion strategy.