Cord-Blood Derived Chemistry Reference Values in Preterm Infants for Sodium, Chloride, Potassium, Glucose, and Creatinine

Abstract

Objectives: Guidelines recommend preterm infants be supported to maintain their serum electrolytes within “normal” ranges. In term babies, cord blood values differed in pathological pregnancies from healthy ones. Study design: We examined cord blood sodium, chloride, potassium, glucose, and creatinine to derive maturity-related reference intervals. We examined associations with gestational age, delivery mode, singleton versus multiple, and prenatal maternal adverse conditions. We compared preterm cord values to term, and to adult reference ranges. Results: There were 591 infants, 537 preterm and 54 term. Preterm cord glucose levels were steady (3.7+/-1.1mmol/l), while sodium, chloride and creatinine increased over GA by 0.17, 0.14 and 1.07 micromol/week respectively (p<0.003). Average preterm cord potassium and chloride were higher than term (p<0.05). Compared to adult reference intervals, cord preterm reference intervals were higher for chloride (100-111 vs 98-106 mmol/l), lower for creatinine (29-84 vs 62-115 micromol/l), more variable for potassium (2.7-7.9 vs. 3.5-5.0 mmol/l) and sodium (130-141 vs. 136-145 mmol/l). Cesarean section was associated with higher potassium and lower glucose; multiple births with higher chloride and creatinine and lower glucose; SGA with lower glucose. Conclusions: Cord blood values vary across the GA range with increases in sodium, chloride and creatinine while glucose remained steady. Average preterm reference values were higher than term values for potassium and chloride. Preterm reference values differed from published adults’ reference values. The varies across GA and by delivery mode, SGA, and being a multiple, which may have direct implications for neonatal care and fluid management.