Supplementary Material for: Blood lactate levels during therapeutic hypothermia and neurodevelopmental outcome or death at 18 -24 months of age in neonates with moderate and severe hypoxic-ischemic encephalopathy

Introduction: Blood lactate levels in neonates with hypoxic ischemic encephalopathy (HIE) vary and their impact on neurodevelopmental outcome is unclear. We assessed blood lactate course over time in neonates with HIE during therapeutic hypothermia and investigated if blood lactate values were associated with neurodevelopmental outcome at two years of age.
Methods: This is a retrospective cohort study of neonates with HIE born between 2013-2019, treated at the University Children’s Hospital Zurich. We recorded blood lactate values over time and calculated time until lactate was ≤ 2 mmol/L. Neurodevelopmental outcome was assessed at 18 - 24 months of age using the Bayley Scales of Infant and Toddler Development - Third Edition (BSID-III) and categorized as favorable or unfavorable. We investigated associations between blood lactate values and outcome using logistic regression and adjusted for Sarnat stage.
Results: 33/45 neonates (69%) had a favorable and 14 (31%) an unfavorable neurodevelopmental outcome.
Mean initial lactate values were lower in the favorable (13.9 mmol/L, SD 2.9) versus unfavorable group (17.1 mmol/L, SD 3.2; p= 0.002). Higher initial and maximal blood lactate levels were associated with unfavorable outcome, also when adjusted for Sarnat stage (aOR 1.37; 95% CI 1.01-1.88; p= 0.046 and aOR 1.35; 95% CI 1.01-1.81; p= 0.041, respectively).
Conclusion: In neonates with HIE receiving TH initial and maximal blood lactate levels were associated with neurodevelopmental outcome at 18 - 24 months of age also when adjusted for Sarnat stage. Further investigations to analyze blood lactate as a biomarker for prognostic value are needed.