Association of Rewarming Rate on Neonatal Outcomes in Extremely Low Birth Weight Infants with Hypothermia

Objective To explore the possible association between rewarming rate and neonatal outcomes in extremely low birth weight infants (ELBWIs) with hypothermia. Study design All ELBWIs with hypothermia (temperature <36.0°C) on neonatal intensive care unit (NICU) admission were retrospectively evaluated. Rewarming rate was analyzed as both a dichotomous (≥0.5°C/h rapid group; <0.5°C/h slow group) and a continuous variable. Multivariable analysis was performed to explore the relation between rewarming rate and several outcomes, adjusting for clinically relevant confounders. Results Hypothermia on NICU admission was present in 182 out of 744 ELBWIs (24.5%). The rewarming rate was slow in 109 subjects (59.9%) and rapid in 73 subjects (40.1%), with a median rewarming rate of 0.29°C/h (IQR 0.2-0.35) and 0.76°C/h (IQR 0.61-1.09), respectively (P <.0001). The median rewarming time was 340 minutes (IQR 250-480) and 170 minutes (IQR 110-230), respectively (P <.0001). After adjusting for clinically relevant confounders, we did not find significant associations between rewarming rate group (≥0.5°C/h vs <0.5°C/h) and neonatal outcomes. When we considered the rewarming rate as continuous variable, a higher rewarming rate was identified as a protective factor for respiratory distress syndrome (OR 0.39, 95% CI 0.17-0.87; P =.02). Conclusions In ELBWIs with hypothermia upon NICU admission, there were no significant differences between rapid or slow rewarming rate and major neonatal outcomes. A higher rewarming rate was associated with a reduced incidence of respiratory distress syndrome.