Clinical and prognostic value of calcium and phosphorus levels as possible markers of endothelial dysfunction in preterm infants

Abstract

The system maintaining a sufficient level of calcium and phosphorus is formed only by the end of the first month of life, and in pretermure infants even later. These elements play a crucial role in many physiological processes. They also affect vascular function, endothelium, and endothelial nitric oxide (NO) synthase. Therefore, the aim of our study was to analyze the relationship of serum phosphorus and calcium levels with markers of endothelial dysfunction and features of the early neonatal period. The study included 37 preterm infants that received standard clinical, laboratory, and instrumental examination. As markers of endothelial dysfunction, the 4a/4b polymorphism of the eNOS gene was investigated and quantitative measurement of NO metabolites in urine was performed. Phosphorus and calcium levels in 37 preterm infants on the first day were 4.06 ± 1.88 mg/dL and 1.89 ± 2.08 mg/dL, and on the six day 4.89 ± 2.02 mg/dL and 1.86 ± 1.80 mg/dL, respectively. Combined hypocalcemia and hypophosphatemia were found in 27 (73.0%) of 37 examined infants. The presence of severe condition in early neonatal period was positively correlated with calcium levels on the first and sixth days after birth. There were determined positive correlation between calcium and phosphorus levels on the first day after birth and severity of clinical symptoms in neonatal period and birth gestational age. Serum calcium level in preterm birth infants was positively correlated with respiratory failure on the sixth day. Correlation between calcium and phosphorus serum levels was observed for severe and stable infants on the first day, but on the six day only in preterm birth infants with stable condition. We have not found an association between phosphorus and calcium levels and markers of endothelial dysfunction in preterm birth infants. Serum phosphorus and calcium levels and studied markers of endothelial dysfunction have been found to be independent markers of the risk of developing a complicated early neonatal period in preterm infants.