Brain Injury Patterns and Short-TermOutcomes in Late Preterm Infants Treated with Hypothermia for Hypoxic Ischemic Encephalopathy.

Hypoxic-ischemic encephalopathy (HIE) is a leading cause of severe neurological impairments in childhood. Therapeutic hypothermia (TH) is both safe and effective in neonates born at ≥36 weeks gestation with moderate to severe HIE. We aimed to evaluate short-term outcomes-including brain injury detected on magnetic resonance imaging (MRI)-in infants born at 34-35 weeks of gestation drawing on our clinical experience with neonates under 36 weeks of gestational age (GA). In this retrospective cohort study, 20 preterm infants with a GA of 34 to 35 weeks and a matched cohort of 80 infants with a GA of ≥36 weeks who were diagnosed with moderate to severe HIE and underwent TH were included. Infants were matched in a 1:4 ratio based on the worst base deficit in blood gas and sex. Maternal and neonatal characteristics, brain MRI findings and short term outcomes were compared. Infants with a GA of 34-35 weeks had a lower birth weight and a higher rate of caesarean delivery (both < 0.001). Apgar scores, sex, intubation rate in delivery room, blood gas pH, base deficit and lactate were comparable between the groups. Compared to infants born at ≥36 weeks of GA, preterm neonates were more likely to receive inotropes, had a longer time to achieve full enteral feeding, and experienced a longer hospital stay. The mortality rate was 10% in the 34-35 weeks GA group. Neuroimaging revealed injury in 66.7% of infants born at 34-35 weeks of gestation and in 58.8% of those born at ≥36 weeks ( = 0.56). Injury was observed across multiple brain regions, with white matter being the most frequently affected in the 34-35 weeks GA group. Thalamic and cerebellar abnormal signal intensity or diffusion restriction, punctate white matter lesions, and diffusion restriction in the corpus callosum and optic radiations were more frequently detected in infants born at 34-35 weeks of gestation. Our study contributes to the growing body of literature suggesting that TH may be feasible and tolerated in late preterm infants. Larger randomized controlled trials focused on this vulnerable population are necessary to establish clear guidelines regarding the safety and efficacy of TH in late preterm infants.