Time to Reaching Target Cooling Temperature and 2-year Outcomes in Infants with Hypoxic-Ischemic Encephalopathy

Objective To determine if time to reaching target temperature (TT) is associated with death or neurodevelopmental impairment (NDI) at 2 years of age in infants with hypoxic-ischemic encephalopathy (HIE). Study design Newborn infants >= 36 weeks of gestation diagnosed with moderate or severe HIE and treated with therapeutic hypothermia were stratified based on time at which TT was reached, defined as early (ie, <= 4 hours of age) or late (>4 hours of age). Primary outcomes were death or NDI. Secondary outcomes included neurodevelopmental assessment with Bayley Scales of Infant and Toddler Development, third edition (BSID-III) at age 2. Results Among 500 infants, the median time to reaching TT was 4.3 hours (IWR, 3.2-5.7 hours). Infants in early TT group (n = 211 [42%]) compared with the late TT group (n = 289 [58%]) were more likely to be inborn (23% vs 13%; P < .001) and have severe HIE (28% vs 19%; P = .03). The early and late TT groups did not differ in the primary outcome of death or any NDI (adjusted RR, 1.05; 95% CI, 0.85-0.30; P = .62). Among survivors, neurodevelopmental outcomes did not differ significantly in the 2 groups (adjusted mean difference in Bayley Scales of Infant Development-III scores: cognitive, -2.8 [95% CI, -6.1 to 0.5], language -3.3 [95% CI, -7.4 to 0.8], and motor -3.5 [95% CI, -7.3 to 0.3]). Conclusions In infants with HIE, time to reach TT is not independently associated with risk of death or NDI at age 2 years. Among survivors, developmental outcomes are similar between those who reached TT at <4 and >= 4 hours of age.