High early fluid and sodium intake as risk factors for acute kidney injury in very-low-birthweight infants

Background Acute kidney injury (AKI) is common in very-low-birthweight (VLBW) infants. Both fluid overload and dehydration can lead to AKI. Our aim was to examine the associations between early fluid and sodium intake and AKI. Methods This retrospective cohort study comprised 421 VLBW infants born at < 32 weeks. Detailed data on fluid management during the first 24 h of life, diuresis and weight changes during the first postnatal week and plasma creatinine measurements during the first 2 postnatal weeks were acquired from an electronic patient information system. AKI was defined according to the KDIGO definition modified for neonates. Results The incidence of AKI was 8.6%, and on average, it was diagnosed on the fifth postnatal day. Higher total fluid intake (mL/kg/24 h) during the first day of life was associated with an increased risk of AKI (OR, 1.015; 95% CI, 1.005–1.025; p < 0.01), analysis adjusted for gestational age and being small-for-gestational age. The highest fluid intake quartile had a 5.6-fold risk of developing AKI when compared with the lowest quartile ( p = 0.01). A higher total sodium intake (mmol/kg/24 h) was associated with an increased risk of AKI (OR, 1.12; 95% CI, 1.03–1.21; p < 0.01). Among infants with AKI, a substantial proportion of early fluid and sodium intake (median 27% and 59% of total intake, respectively) originated from volume expanders. Infants diagnosed with AKI exhibited an average weight gain of + 2.8% by the second day of life. Conclusions As part of efforts to minimize the risk of AKI, avoiding excessive fluid and sodium administration during the first postnatal hours may be beneficial.