Non-oliguric hyperkalemia in neonates less than 30 weeks of gestation: clinical characteristics and outcomes

Hyperkalemia is a frequent electrolyte imbalance in very preterm infants, often occurring in the first 72 hours of life. A unique entity, non-oliguric hyperkalemia (NOHK), is characterized by elevated serum potassium despite adequate urine output. While frequently reported, its risk factors, biochemical profile, and outcomes remain inadequately understood, particularly in low- and middle-income countries. To determine the incidence, maternal and neonatal risk factors, biochemical profile, and outcomes associated with NOHK in preterm neonates between 26⁺⁰ and 30⁺⁰ weeks' gestation, we conducted a retrospective cohort study in a tertiary neonatal intensive care unit (NICU) in South India. Infants born between 26⁺⁰ and 30⁺⁰ weeks' gestation and surviving beyond 12 hours during the 2-year study period were eligible. Infants born at <26⁺⁰ weeks were excluded due to variability in care practices during the study period, including the provision of comfort care. Other exclusions included congenital renal anomalies, acute kidney injury, hemolyzed samples, and incomplete records. NOHK was defined as serum potassium >6.5 mmol/l within 72 hours with urine output ≥1 ml/kg/h. Maternal, perinatal, and neonatal variables were extracted. Outcomes included mortality and major morbidities. Statistical comparisons used Mann-Whitney U and Chi-square/Fisher's exact tests; multivariate logistic regression adjusted for gestational age, antenatal steroids, Doppler abnormalities, and hypocalcemia. Of the total 159 eligible infants, 59 (37.1%) developed NOHK. Lower gestational age and hypocalcemia (18.6% vs. 2%, OR 11.2, p < 0.001) were significant risk factors. NOHK infants had higher blood urea nitrogen, though creatinine and sodium were comparable. Mortality was significantly higher in NOHK (11.9% vs. 2%, p = 0.001) and remained independently associated after adjustment. Morbidities such as bronchopulmonary dysplasia, retinopathy of prematurity, intraventricular hemorrhage, and patent ductus arteriosus did not differ.