Authors
E. Williams, K. Tamura, T. Dassios, A. Pahuja, K. Hunt, V. Murthy, P. Bhat, R. Bhat, A. Milner, A. Greenough

Institution(s): Faculty of Life Sciences and Medicine, King’s College London, UK & Neonatal Intensive Care Unit, King’s College Hospital NHS Foundation Trust, UK

Introduction
Abnormal carbon dioxide (CO2) levels within the neonatal period are associated with intraventricular haemorrhage (IVH) development in prematurely born infants. The aim of this study was to establish whether CO2 levels in the first 72 hours post-delivery reflected abnormal levels during resuscitation and hence a prolonged rather than initial insult results in cerebral damage. Furthermore, we determined if those infants exposed to the largest fluctuations in EtCO2 levels during resuscitation would be at greater risk of developing

Methods
A retrospective study of infants born at less than 33 weeks of gestational age who required resuscitation in the delivery suite was performed. Resuscitation recordings were analysed and the highest and lowest levels of end tidal CO2 (EtCO2) alongside the degree of fluctuation of EtCO2 (delta EtCO2) were calculated. Blood gases performed in the first three days after birth were analysed and the maximum, minimum and degree of fluctuation in CO2 levels were calculated. IVH were diagnosed by cranial ultrasound examinations. Ethical approval was given by the Outer London Ethics Committee and registered with the trust research and audit

Results
Fifty eight infants were included with a median gestational age of 27.3 (24.9-29.0) weeks and a birthweight of
0.9 (0.72-1.21) kg. Thirteen infants developed a grade 3-4 (severe) IVH. The highest EtCO2 during resuscitation in the no/non-severe IVH group was 8.2 (7.4-9.9) kPa and 10.2 (8.6-11.1) kPa in the severe group, which remained significant after correcting for differences in gestational age between the two groups (p=0.037). There were no strong correlations seen between delivery suite levels of EtCO2 and CO2 levels on the neonatal unit in the first 72 hours. The delta EtCO2 during resuscitation was significantly different between infants with any grade IVH (6.2 (5.4-7.5) kPa) and those with no IVH (3.8 (2.7-4.3) kPa; p<0.001). Delta EtCO2 levels during resuscitation gave an area under the receiver operator characteristic curve of 0.940 for prediction of IVH.

Conclusions
These results emphasize the importance of monitoring EtCO2 levels of prematurely born infants in the delivery suite, as large fluctuations during resuscitation are highly predictive of subsequent IVH development.

References
Pahuja A, Hunt K, Murthy V, Bhat P, Bhat R, Milner AD, Greenough A (2018) Relationship of resuscitation, respiratory function monitoring data and outcomes in preterm infants. Eur J Pediatr 177:1617-1624