Low phosphatemia in extremely low birth weight neonates: A risk factor for hyperglycemia?

Hyperglycemia occurs in more than half of the extremely low birth weight (ELBW) neonates during the first weeks of life, and is correlated with an increased risk of morbi-mortality. Hypophosphatemia is another frequent metabolic disorder in this population. Data from animal, adult studies and clinical observation suggest that hypophosphatemia could induce glucose intolerance. Our aim was to determine whether a low phosphatemia is associated with hyperglycemia in ELBW neonates.

This observational study included ELBW infants admitted in a tertiary neonatal care center (2010-2011). According to the center's policy, they received parenteral nutrition from birth and human milk from day 1. Phosphatemia and glycemia were measured routinely during parenteral nutrition. Hyperglycemia was defined by two consecutives values >8.3 mmol/L (150 mg/dL). Statistical analysis used a joint model combining a mixed-effects and a survival submodels to measure the association between phosphate and hyperglycemia.

The study included 148 patients. Mean gestational (Standard Deviation) age was 27.3 (1.6) weeks; mean birth weight was 803 (124) grams; 57% presented hyperglycemia. The multivariate joint model showed that the hazard of hyperglycemia at a given time was multiplied by 3 for each 0.41 mmol/L decrease of phosphate level at this time (p = 0.002) and by 3.85 for the same decreased of phosphate the day before (p = 0.0015).

To our knowledge, this is the first study suggesting that low phosphatemia can be associated with hyperglycemia in ELBW neonates. Further studies will have to demonstrate whether better control of phosphatemia could help in preventing hyperglycemia.