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

Objective International guidelines recommend that preterm infants should 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 +/- 1.1 mmol/L), while sodium, chloride, and creatinine increased over GA by 0.17, 0.14 mmol/L/week, and 1.07 mu mol/L/week, respectively ( p < 0.003). Average preterm cord potassium and chloride were higher than the term ( p < 0.05). Compared with 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 mu mol/L), and 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, and SGA with lower glucose. Conclusion Cord blood values varied 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 changes across GA and by delivery mode, SGA, and being a multiple, which may have direct implications for neonatal care and fluid management. Key Points Cord blood electrolyte, creatinine, and glucose values vary across neonatal gestational age. Average preterm cord values of potassium and chloride were higher than term values. Cord reference values differ by delivery mode, growth, and multiple impacting neonatal care decisions.