Despite advances in neonatal care, moderate-to-severe acute perinatal HIE in late preterm and term infants remains a cause of mortality, neurological injury, and long-term neurodevelopmental disability. The current standard of care includes therapeutic hypothermia for 72 hours, but 40-50% of infants will die or suffer significant neurodevelopmental impairment. It has been shown that administration of hydrogen gas (H2) significantly diminishes ischemic injury in swine, and that H2 administration at the dose and duration proposed herein is well-tolerated in healthy adults. The purpose of this project is to test the feasibility and safety of H2 administration as an adjunct to therapeutic hypothermia in infants with HIE. Under exemption from informed consent, infants with severe, acute brain injury at birth will be randomized to standard therapy with or without the administration of 2% hydrogen in gases administered via the ventilator, non-invasive ventilation, or nasal cannula for 72 hours.