Association between hypocapnia and ventilation during the first days of life and brain injury in asphyxiated newborns treated with hypothermia

Purpose: Therapeutic hypothermia is the standard treatment for asphyxiated newborns. Since hypocapnia is common in these newborns, the aim of this study was to assess the association among hypocapnia, ventilation, and brain injury. Methods: We conducted a retrospective cohort study of all asphyxiated newborns treated with hypothermia from 2008 to 2014. Partial pressure of carbon dioxide (pCO(2)), ventilatory status, and modes of ventilation were recorded during the first 4 days of life. Brain injury was evaluated using brain magnetic resonance imaging. Differences between intubated and nonintubated newborns and between the newborns who developed brain injury or not were assessed. Results: One hundred ninety-eight asphyxiated newborns were treated with hypothermia. During the first 2 days of life, intubated newborns had consistently lower pCO(2) levels (respectively, 29.01 +/- 8.55, p < .001 on day 1 of life and 33.65 +/- 7.12, p = .004 on day 2 of life). Fifty-nine percent of the intubated newborns developed brain injury versus only 43% of the nonintubated newborns (p = .046). The lowest pCO(2) levels averaged over the first 4 days of life were significantly decreased in newborns developing brain injury (p = .02) and significantly associated with brain injury severity (p = .01). After adjusting for potential cofounders, the lowest pCO(2) averaged over days 1-4 of life remained significantly associated with an increased risk of brain injury (odds ratio [95%CI]: 1.07 [1.00-1.14]; p = .04). Conclusions: Intubated and ventilated asphyxiated newborns experienced more severe hypocapnia, and had higher incidences of brain injury. Hypocapnia during the first 4 days of life was associated with an increased risk of developing (more severe) brain injury.