Abstract
Background: Increasing evidence suggests that hypocapnia is associated with brain injury on MRI and adverse neurodevelopmental outcome in infants treated with therapeutic hypothermia (TH) for neonatal encephalopathy (NE). Consequently, continuous carbon dioxide (CO2) monitoring and avoiding extreme levels of CO2 have the potential to improve neurologic outcome. Our aim was to compare changes in transcutaneous CO2 levels during hypothermia and rewarming between infants with and without brain injury on MRI in a cohort of infants with neonatal encephalopathy.
Methods: This prospective observational trial enrolled infants, who received TH for mild to severe NE between October 2019 and June 2022.The pattern of brain injury was evaluated according to an MRI grading system. We identified 2 groups of patients with and without any brain injury based on the assessment of MRI after rewarming. Transcutaneous CO2 (PtcCO2) data were captured by a real-time integrated neuromonitoring system.
Results: 110 infants received TH during study period, out of those 37 infants were enrolled into this prospective study. Serial measurements from 31 patients were available for analysis. Sixteen (51.6%) infants had evidence of any brain injury on MRI. Integrated monitoring began at median 24 hours of life (min-max: 11-51) and ended at median 94 (min-max: 87-120) hours of life. Results from mixed models indicated a significant effect of phases/time on mean PtcCO2 level (F = 4.4, P = 0.001), but no difference by brain injury status (F = 0.0, P = 0.304) or an interaction effect (F = 1.2, P = 0.304) (Figure 1). Mean levels of PtcCO2 exhibited a significant decrease between the last phase of TH (> 60 hours of life) and post-rewarming phase: mean difference: -3.76, 95%CI -6.7; -0.8, P = 0.003
Conclusions: This novel longitudinal study of infants with NE showed relatively stable PtcCO2 levels within the normal range during hypothermia and rewarming. Results from mixed models indicated a significant effect of time on transcutaneous CO2 levels. Based on the results adjusted for multiple comparisons, the comparison that met statistical significance was the decline between the last phase of hypothermia (> 60 hours of life) and post-rewarming phase. The trajectories of PtcCO2 did not differ between infants with and without brain injury. These pilot results are needed to be interpreted with caution given study limitations that include no adjustment for potential confounding or data collection during the early hours of life.
Footnotes
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