Influence of timing of initiation of therapeutic hypothermia on brain MRI and neurodevelopment at 18 months in infants with HIE: a retrospective cohort study

OBJECTIVE: To examine the influence of timing of initiation of therapeutic hypothermia (TH) on brain injury on MRI and on neurodevelopmental outcomes at 18 months. DESIGN: Retrospective cohort study. SETTING: Tertiary neonatal intensive care unit in Ontario, Canada. PATIENTS: Ninety-one patients with hypoxic ischaemic encephalopathy (HIE) were included, 54 in the early TH group and 37 in the late TH group. INTERVENTION: Whole-body hypothermia administered for 72 hours, initiated either before 3 hours of life (early TH) or between 3 and 6 hours of life (late TH). MAIN OUTCOME MEASURES: Brain injury on MRI after TH (assessed by two neuroradiologists), and neurodevelopmental outcomes at 18 months old. RESULTS: TH was initiated at a median time of 1.4 hours (early TH) and 4.4 hours (late TH). Sixty-four neonates (early TH=36, late TH=28) survived and completed neurodevelopmental assessment at 18 months. Neonates in the early TH group received more extensive resuscitation than neonates in the late TH group (p=0.0008). No difference was observed between the two groups in the pattern or severity of brain injury on MRI, or in the neurodevelopmental outcomes at 18 months. The non-survivors (n=16) had lower Apgar scores at 10 min, more extensive resuscitation, suffered from more severe HIE and had significantly more abnormal cerebral function monitoring. CONCLUSION: In this retrospective cohort study, TH initiated early was associated neither with a difference in brain injury on MRI nor better neurodevelopmental outcomes at 18 months.