Moderate hyperoxic versus near-physiological oxygen targets during and after coronary artery bypass surgery: A randomised controlled trial

Abstract

Background: The safety of perioperative hyperoxia is currently unclear. Previous studies in patients undergoing coronary artery bypass surgery suggest reduced myocardial damage when avoiding extreme perioperative hyperoxia (>400 mmHg). In this study we investigated whether an oxygenation strategy from moderate hyperoxia to a near-physiological oxygen tension reduces myocardial damage and improves haemodynamics, organ dysfunction and oxidative stress. Methods: This was a single-blind, single-centre, open-label, randomised controlled trial in patients undergoing elective coronary artery bypass surgery. Fifty patients were randomised to a partial pressure of oxygen in arterial blood (PaO2) target of 200-220 mmHg during cardiopulmonary bypass and 130-150 mmHg during intensive care unit (ICU) admission (control group) versus lower targets of 130-150 mmHg during cardiopulmonary bypass and 80-100 mmHg at the ICU (conservative group). Primary outcome was myocardial injury (CK-MB and Troponin-T) at ICU admission and 2, 6 and 12 hours thereafter. Results: Weighted PaO2 during cardiopulmonary bypass was 220 mmHg (interquartile range (IQR) 211-233) vs. 157 (151-162) in the control and conservative group, respectively (P < 0.0001). During ICU admission, weighted PaO2 was 107 mmHg (86-141) vs. 90 (84-98) (P = 0.03), respectively. Area under the curve of CK-MB was median 23.5 μg/L/h (IQR 18.4-28.1) vs. 21.5 (15.8-26.6) (P = 0.35) and 0.30 μg/L/h (0.25-0.44) vs. 0.39 (0.24-0.43) (P = 0.81) for Troponin-T. Cardiac index, systemic vascular resistance index, creatinine, lactate and F2-isoprostane levels were not different between groups. Conclusions: Compared to moderate hyperoxia, a near-physiological oxygen strategy does not reduce myocardial damage in patients undergoing coronary artery bypass surgery. Conservative oxygen administration was not associated with increased lactate levels or hypoxic events. Trial registration: Netherlands Trial Registry NTR4375 , registered on 30 January 2014