Association of hypermagnesemia at birth and admission hypothermia in pre-term infants: A secondary analysis of a prospective cohort study.

BACKGROUND: Hypothermia on admission is associated with increased mortality in preterm infants. Drugs administered to pregnant women is implicated in its occurrence. Since magnesium sulfate has a myorelaxant effect, we aimed evaluating the association of hypermagnesemia at birth and admission hypothermia (axillary temperature <36.5°C) in preterm infants.

METHODS: We performed a secondary analysis of a prospective cohort study database including inborn infants <34 weeks, without congenital malformations. Hypermagnesemia was considered if the umbilical magnesium level >  2.5 mEq/L. Maternal and neonatal variables were used to adjust the model, submitted to the multivariate hierarchical modelling process.

RESULTS: We evaluated 249 newborns with median birth weight and gestational age of 1375 (IQR 1020-1375) g and 31 (IQR 28-32) weeks, respectively. Hypermagnesemia occurred in 28.5% and admission hypothermia occurred in 28.9% . In the univariate analysis, the following variables were identified as being associated with admission hypothermia: hypermagnesemia (OR 3.71; CI 2.06-6.68), resuscitation (OR 2.39; CI 1.37-4.19), small to gestational age (OR 1.91; CI1.03-3.53), general anesthesia (OR 3.34; CI 1.37-8.13), birth weight (OR 0.998; CI 0.998-0.999) and gestational age (OR 0.806; CI 0.725-0.895). In the hierarchical regression model, hypermagnesemia remained independent associated with admission hypothermia (OR 3.20; CI 1.66-6.15), as well as birth weight (OR 0.999; CI 0.998-0.999) and tracheal intubation (3.83; CI 1.88-7.80).

CONCLUSION: Hypermagnesemia was associated with an increased risk of admission hypothermia, as did tracheal intubation and lower birth weight.