Fluid Balance in Infants Born at 22-23 Weeks of Gestation: Trajectories and Associations with Outcomes

Abstract

Objectives: To investigate fluid balance, sodium intake, and hyperglycemia during the first 2 weeks of life in infants born at 22-23 weeks of gestational age, and to examine their associations with hospital outcomes.

Study design: Retrospective, single-center, cohort study of all infants surviving beyond 72 hours (22-23 weeks; January 2019-June 2024). Total fluid intake, weight, and urine output were collected during the first 14 days, and used to calculate daily insensible water loss. Daily intake of sodium, plasma sodium and glucose levels, and the occurrence of acute kidney injury (AKI) were recorded. Relationships with bronchopulmonary dysplasia, patent ductus arteriosus, necrotizing enterocolitis, and death were analyzed.

Results: Survival until discharge was 57% (39/69). The nadir weight loss was -15 ± 6% (mean ± SD) at median 3 (IQR 2-5) days. Average total fluid intake during the first week of life was 176 ± 25 mL/kg/day; peak mean urine output (119 ± 39 mL/kg/day) and insensible water loss (87 ± 54 mL/kg/day) occurred at days 2 and 5, respectively. The median daily sodium intake was 4.6 and 4.5 mmol/kg/day in the first and second weeks, respectively. Hypernatremia (plasma sodium >150 mmol/L) occurred in 42% and prolonged (>2 days) hyperglycemia (plasma glucose >10 mmol/L) was frequent (87%). AKI occurred in 28%. Mortality was independently associated with weight loss >15% (OR: 3.9, 95% CI: 1.4-11.1, P = .013), and AKI (OR: 3.5, 95% CI: 1.1-11.3, P = .034).

Conclusions: In infants born at 22-23 weeks of gestation, a large loss of body weight and AKI are prevalent during the first 2 weeks of life and are associated with increased mortality. Preventing excessive weight loss might improve outcomes.

Keywords: acute kidney injury; dehydration; extreme prematurity; hyperglycemia; hypernatremia; immaturity; insensible water loss; skin.