Admissions and outcomes after perinatal asphyxia and hypoxic-ischaemic encephalopathy before and after therapeutic hypothermia: a retrospective population-based study.

Background: Hypoxic-ischaemic encephalopathy (HIE) is the leading cause of brain injury in term infants, and therapeutic hypothermia (TH) has been shown to improve outcomes for infants with moderate/severe HIE. We aimed to describe admission rates and outcomes after perinatal asphyxia and HIE before and after the implementation of TH in June 2007.

Methods: This single-centre, retrospective, population-based study included term/near-term infants born between January 2003 and December 2011 and admitted to a level III neonatal unit with International Statistical Classification of Diseases and Related Health Problems, 10th Revision diagnoses P20, P21, P90 and/or P91, and a clinical picture compatible with asphyxia/HIE. Outcome measures were clinical characteristics during neonatal admission and survival without cerebral palsy (CP) at 9-10 years. Data were collected from medical records and the Norwegian Quality and Surveillance Registry for CP.

Results: The admission rate related to perinatal asphyxia was 7.63 per 1000 term/near-term live births and did not change over time. The incidence of HIE increased significantly after the implementation of TH (from 2.69 to 4.21 per 1000 term/near-term live births, incidence rate ratio 1.56 (95% CI 1.06 to 2.34)). Among 255 included infants (62% boys, mean birth weight 3691 g), significantly more infants were diagnosed with HIE after the implementation of TH compared with before (54% vs 36%, respectively, p=0.005). A total of 227 (92%) of 247 infants survived without CP, with no difference between the time periods. Among infants with moderate/severe HIE born after the implementation of TH, 20 (67%) of 30 infants were cooled and 80% of cooled and 33% of non-cooled infants survived without CP.

Conclusions: Admission rates and outcomes were stable during these 9 years, but more infants were reported with HIE after the implementation of TH. Non-cooled infants with moderate/severe HIE born after the implementation of TH had poor outcomes, and early clinical HIE evaluation remains a major challenge.