Hypoglycemia is the most common metabolic problem seen in newborn infants. The overall incidence of neonatal hypoglycemia varies from 1.3 to 3 per 1,000 live births (Adamkin & American Academy of Pediatrics, 2011). This variability is seen due in part to the controversial definition of neonatal hypoglycemia in addition to the different populations, different method and timing of feeding, and different types of glucose testing. For example, serum glucose levels are higher than whole blood values. The controversial definition is reinforced by the American Academy of Pediatrics statement, which notes that “there has been no substantial evidence-based progress in defining what constitutes clinically important neonatal hypoglycemia particularly regarding how it relates to brain injury, and that monitoring for, preventing, and treating neonatal hypoglycemia remain largely empirical.” In other words, the level or duration of hypoglycemia that is harmful to an infant’s developing brain is not known.
The laboratory value used to define neonatal hypoglycemia varies in part because of the normal physiologic changes a newborn experiences as he or she transitions to extrauterine life. The healthy neonate demonstrates a drop in the blood glucose concentrations to approximately 30 mg/dL within 1 to 2 hours after birth, and typically returns to more than 45 mg/dL with normal feeding within 12 hours (Cornblath et al., 2000).
Neonatal hypoglycemia is a result of an imbalance between glucose supply and the metabolic needs of the neonate, which may be because of inadequate glycogen stores, inappropriate changes in insulin secretion, inadequate muscle stores as a source of amino acids for gluconeogenesis, or inadequate lipid stores for the release of fatty acids, or increased glucose utilization from sepsis or other illnesses (Deshpande & Ward Platt, 2005). Excluding infants who are receiving insulin therapy, almost all hypoglycemia in the neonate occurs during fasting. Postprandial hypoglycemia is rare in neonates but may be seen with hyperinsulinism, or persistent hyperinsulinemic hypoglycemia of infancy (PHHI). PPHI is the most common cause of hypoglycemia in the first 3 months of life. It is well recognized in infants of mothers with diabetes. The etiology for hyperinsulinism is the fetal response to elevated maternal glucose by producing elevated levels of insulin. Following birth, the insulin concentrations are inappropriately elevated and lead to neonatal hypoglycemia. Most cases of hyperinsulinism are transient; however, prolonged neonatal hyperinsulinism, also known as “congenital hyperinsulinism,” is most commonly associated with an abnormality of beta-cell regulation throughout the pancreas. In rare cases, surgical treatment is necessary 171for the neonate who is unresponsive to conventional therapy. Surgical treatment involves resection of 80% to 90% of the pancreas (Garg & Devaskar, 2006).