Letter

Early fluid intake and chronic lung disease

Neonatal intraventricular hemorrhage prevention bundles for preterm infants commonly defer daily weighing for the first 72 h, with reweighing occurring on day 4. Clinicians rely on maintaining stable sodium values as a proxy of fluid status to inform fluid management decisions over the first 96 h after birth. Yet, there exists a paucity of research evaluating whether serum sodium or osmolality are appropriate proxies for weight loss and whether increasing variability in sodium or osmolality during this early transitional period is associated with adverse in-hospital outcomes.

To evaluate whether serum sodium or osmolality change in the first 96 h after birth was associated with percent weight change from birth weight, and to assess potential associations between serum sodium and osmolality variability with in-hospital outcomes.

This retrospective, cross-sectional study included neonates born at ≤30 gestational weeks or ≤1250 g. We evaluated associations between serum sodium coefficient of variation (CoV), osmolality CoV, and maximal weight loss percentage in the first 96 h after birth with in-hospital neonatal outcomes.

Among 205 infants, serum sodium and osmolality were poorly correlated with percent weight change in individual 24-h increments (R² = 0.01–0.14). For every 1% increase in sodium CoV, there was an associated 2-fold increased odds of surgical necrotizing enterocolitis and 2-fold increased odds of in-hospital mortality (odds ratio, 2.07; 95% CI: 1.02, 4.54; odds ratio, 1.95; 95% CI: 1.10, 3.64, respectively). Sodium CoV was more strongly associated with outcomes than absolute sodium maximal change.

In the first 96 h, serum sodium and osmolality are poor proxies for assessing percent weight change. Increasing variability of serum sodium is associated with later development of surgical necrotizing enterocolitis and all-cause in-hospital mortality. Prospective research is needed to evaluate whether reducing sodium variability in the first 96 h after birth, as assessed by CoV, improves newborn health outcomes.

Un adecuado balance hídrico en los recién nacidos prematuros con extremo bajo peso al nacer es fundamental para la disminución de la morbimortalidad en los primeros días de vida. Con frecuencia, el manejo del balance hídrico es causa de confusión y mucha dedicación de tiempo entre especialistas. Uno de los elementos fundamentales, es precisar las pérdidas hídricas transepidérmicas y respiratorias, lo que se conoce como pérdidas insensibles. El objetivo de esta revisión es fundamentar los conceptos principales y sintetizar las formas habitualmente empleadas en este procedimiento, a través de una fórmula matemática de fácil aplicación y posible de llevar a una planilla de cálculos, para así simplificar este proceso y las indicaciones de fluidos derivadas.

An adequate fluid balance in extremely low birth weight newborns is essential to reducing morbidity and mortality during the first days of life. Fluid balance management in these newborns is often confusing and time consuming. Key to this process is correctly identifying transepidermal and respiratory water losses, known as insensitive losses. The purpose of this revision is to review the main concepts in this area and synthesize the habitual formulas utilized in fluid balance management in a spreadsheet that simplifies this process and consequent prescriptions.