Introduction Elevated carbon dioxide (CO2) blood levels have a depressant effect on the central nervous system and can lead to coma in adults. Less is known about the effect of CO2 on the neurological function of infants.
Objective To describe the effect of acute severe hypercapnia (PaCO2 >70 mm Hg) on amplitude-integrated electroencephalography (aEEG) and cerebral oxygenation in newborn infants.
Study design Observational study of full-term and preterm infants with acute severe hypercapnia (identified by arterial blood gas measurements), monitored with aEEG. Visual analysis of the aEEG was performed in all infants. In preterm infants <32 weeks postmenstrual age (PMA), analysis of two-channel EEG was performed. Mean spontaneous activity transients (SAT) rate (SATs/min), interval between SATs (ISI in seconds) and the ISI percentage (ISP) were calculated for 10-min periods before, during and after hypercapnia. Mean regional cerebral oxygen saturation (rScO2) and fractional tissue oxygen extraction (FTOE) measured with near-infrared spectroscopy were also calculated for these periods.
Results Twenty-five infants (21 preterm, 4 full-term) comprising 32 episodes of acute severe hypercapnia were identified. Twenty-seven episodes were accompanied by a transient aEEG depression. Twenty-two episodes in 15 preterm infants <32 weeks PMA were quantitatively analysed. During hypercapnia, SAT rate decreased and ISI and ISP increased significantly. No significant change occurred in rScO2 or FTOE during hypercapnia.
Conclusion Profound depression of brain activity due to severe hypercapnia is also seen in infants. It can be recognised by an acute depression of the aEEG, without clinically detectable changes in cerebral oxygenation.
- cortical activity
- cerebral oxygenation
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Contributors LCW involved in the study design, data collection, data analysis and drafting this manuscript. LMLD involved in the study design, assisted with data analysis and revision of the manuscript. FG assisted with data analysis and revision of the manuscript. PMAL involved in the study design and revision of the manuscript. KPD involved in the initiation of the study, data collection and revision of the manuscript. PA involved in data collection and revision of the manuscript. LSdV involved in the initiation of the study, study design, data analysis and revision of the manuscript. MCT involved in the study design, data analysis and revision of the manuscript.
Funding Lauren Weeke was supported by the European Community's 7th Framework Programme (HEALTH-F5-2009-4.2-1, grant agreement no. 241479, the NEMO project) and by a Wellcome Trust Strategic Translational Award (098983).
Competing interests None declared.
Ethics approval Ethical approval was waived for this study by the EC of the UMC Utrecht and the Maxima Medical Centre because only anonymous retrospective data analysis was performed
Provenance and peer review Not commissioned; externally peer reviewed.