Supplementary Material for: The Effect of Blood Glucose and pCO<sub>2</sub> on Spectral EEG of Premature Infants during the First Three Days of Life

<b><i>Background:</i></b> Spectral EEG analysis using automated quantification of total absolute band power (tABP) expresses brain function. We hypothesized that pCO<sub>2</sub> or blood glucose affects tABP during the critical first days of life in premature infants. <b><i>Objective:</i></b> To use automated tABP quantification to determine whether EEG background activity in premature infants during the first 3 days of life is influenced by pCO<sub>2</sub> or blood glucose levels. <b><i>Methods:</i></b> Preterm infants, group 1 [gestational age (GA) = 24-27 weeks] and group 2 (GA = 28-30 weeks), underwent continuous EEG monitoring for 3 days after birth. Biochemical data were extracted from the observational datasheet used during monitoring. Blood samples were taken at the request of the attending physician. Statistical analyses were performed as repeated measurements using linear mixed models with a random intercept. The effect of time was treated as a fixed covariate and the GA groups as a fixed factor in all models. Continuous data were described using the mean ± SD or median and range, and categorical data were described using the number of patients and percentages unless otherwise indicated. <b><i>Results:</i></b> There was an association between increased pCO<sub>2</sub> and tABP and between increased blood glucose and tABP. Further, there were no differences in the responses between groups 1 and 2. <b><i>Conclusion:</i></b> Both hyperglycemia and hypercapnia showed a negative effect on brain activity decreasing tABP during the first 3 days of life in premature infants.