Hypoglycemia in the neonate: current controversies.

An overview of current controversies in the field of neonatal hypoglycemia is presented. Such controversies include the biochemical definition of hypoglycemia, the methods of monitoring blood glucose concentrations at the bedside, and the effects of hypoglycemia on the brain, together with the relationship between neonatal symptoms, metabolic status and treatment, and neurological outcome. The historical background to this confusion is reviewed, emphasizing that much of this contention arises from analyses of blood glucose concentrations in the first postnatal days, performed on neonates over 30 years ago in which no consideration of the effects of medical management and nutritional policy was taken into account in interpreting the subsequent blood glucose profiles. It is emphasized that there is no evidence to support the perception that the brain of the low birthweight infant is more tolerant to low blood glucose concentrations that that of the fullterm infant. Possible approaches to definition are presented from which it is concluded that the definition of hypoglycemia should be: the lowest concentration of glucose which in combination with other metabolic fuels allows normal brain function. It is emphasized that hypoglycemia is a continuum, no single blood glucose concentration reflecting functional changes in every infant at that level. Confusion over the diagnosis of hypoglycemia is compounded by the inadequacy of currently available methods of bedside monitoring for blood glucose concentrations in the newborn nursery. A pragmatic approach to monitoring and to treatment is presented, suggesting that any infant at risk with a blood glucose concentration less than 2.6 mmol/L should be monitored thereafter, especially in relation to blood glucose changes before and after feeding. Finally, it is emphasized that the study that needs to be done is one which there is documentation of glucose and other fuel concentrations in relation to neurophysiological function during the newborn period and linked with randomized controlled trials of interventions, with follow-up into later childhood.