Abstract
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 born <30 weeks’ gestation, we conducted a retrospective cohort study in a tertiary neonatal intensive care unit (NICU) in South India. Infants <30 weeks who survived beyond 12 hours over a 2 year period were eligible. Exclusions included congenital renal anomalies, acute kidney injury, hemolyzed samples, or incomplete records. NOHK was defined as serum potassium >6.5 mmol/L within 72 h 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 159 infants <30 weeks, 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 (BUN), though creatinine and sodium were comparable. Mortality was significantly higher in NOHK (11.9% vs. 0%, p=0.001) and remained independently associated after adjustment. Morbidities like bronchopulmonary dysplasia, retinopathy of prematurity, intraventricular hemorrhage, and patent ductus arteriosus did not differ.

Key words: Infant, Premature, Cohort, Electrolyte Imbalance, Hyperkalemia, Neonatal Mortality.