Later cooling within 6 hours and temperatures outside 33–34°C are not associated with dysfunctional autoregulation during hypothermia for neonatal encephalopathy

BACKGROUND: Cooling delays, temperature outside 33–34°C, and blood pressure below the mean arterial blood pressure with optimal cerebral autoregulation (MAP(OPT)) might diminish neuroprotection from therapeutic hypothermia in neonates with hypoxic-ischemic encephalopathy (HIE). We hypothesized that longer time to reach temperature <34°C and having temperature outside 33–34°C would be associated with worse autoregulation and greater brain injury. METHODS: Neonates with HIE had rectal temperature and near-infrared spectroscopy autoregulation monitoring during hypothermia (n=63) and rewarming (n=58). All underwent brain MRI, and a subset received diffusion tensor imaging MRI before day 10 (n=41). RESULTS: Most neonates reached <34°C at 3–6 h of life. MAP(OPT) was identified in 54/63 (86%) during hypothermia and in 53/58 (91%) during rewarming. Cooling time was not related to blood pressure deviation from MAP(OPT). Later cooling was associated with lower ADC scalar in unilateral posterior centrum semiovale but not in other regions. Temperatures above 34°C were associated with blood pressure above MAP(OPT) but not with brain injury. CONCLUSION: In neonates who were predominantly cooled after 3 h, cooling time was not associated with autoregulation or overall brain injury. Blood pressure deviation above MAP(OPT) was associated with temperature above 34°C. Additional studies are needed in a more heterogeneous population.