Determining the association of hyperoxia while on extracorporeal life support with mortality in neonates following Norwood operation

Abstract

Background: Patients requiring extracorporeal life support (ECLS) support post-Norwood operation constitute an extremely high-risk group.

Materials and methods: We retrospectively aimed to evaluate the relationship of hyperoxia with mortality and other clinical outcomes in patients who required ECLS following Norwood operation between January/2010 and December/2020 in a large volume center.

Results: During the study period 65 patients required ECLS post-Norwood. Using receiver operating characteristic (ROC) curve analysis, mean PaO₂ of 182 mmHg in the first 48-hour on ECLS was determined to have the optimal discriminatory ability for mortality (sensitivity 68%, specificity 70%). Of the 65 patients, 52% had PaO₂ > 182 mmHg and were designated as hyperoxia group. Patients in the hyperoxia-group had longer cardiopulmonary bypass time (187 vs. 165 min, p = 0.023), shorter duration from CICU arrival to ECLS-cannulation (13.28 vs. 132.58 h, p = 0.003), higher serum lactate within 2-hours from ECLS-canulation (14.55 vs. 5.80, p = 0.01), higher ECLS flows in the first 4-hours (152.68 vs. 124.14, p = 0.006), and higher mortality (77% vs. 39%, p = 0.005). In the unadjusted-analysis, using a derived cut-point, patients in the hyperoxia-group had 5.15 higher odds of mortality (p = 0.003). However, this association was insignificant when adjusting for confounding variables (p = 0.104). Using a functional status scale, new morbidity (38% vs. 21%), and unfavorable outcomes (13% vs. 5%) were higher in the hyperoxia group. Despite being higher in the hyperoxia group, this did not reach statistical significance.

Conclusion: Neonates with hyperoxia (PaO₂ > 182 Torr) during the first 48-hour of ECLS post-Norwood operation had 5 times higher odds of mortality in the unadjusted analysis, however, this was insignificant when adjusting for confounding variables. Patients in the hyperoxia group had shorter duration from CICU arrival to ECLS-cannulation, higher serum lactate prior to ECLS-canulation, and higher ECLS flows in the first 4-hours, (p < 0.05). Multicenter evaluation of this modifiable risk factor is imperative to improve the care of this high-risk cohort.

Keywords: Extracorporeal Life Support (ECLS); Functional Status Scale (FSS); Hyperoxia; New Morbidity; Norwood Operation; Unfavorable Outcomes; Univentricular Physiology.