Hypoglycemia in the late preterm and full-term neonate.
To describe the identification and management of neonatal hypoglycemia in the late preterm and full-term neonate, to delineate the debated aspects of the definition of hypoglycemia, and to emphasize the importance of identification and management of persistent hypoglycemia.
Hypoglycemia is common in late preterm and term infants (with a prevalence as high as 15–20%) because of an increased number of infants born between 34 and 38 weeks’ gestation over the past 20 years, increasing births of large for gestational age (LGA) infants (a consequence of increasing prevalence of maternal obesity with associated gestational diabetes), and a high prevalence of intrauterine growth restriction (IUGR) (with associated low glycogen and fat stores and hence higher incidence of hypoglycemia) as a consequence of poor prenatal care, smoking, and drug use among pregnant women. Hypoglycemia further complicates transitional conditions such as hypothermia, respiratory distress, and poor feeding.
Glucose is an essential fuel for cellular metabolism and is the primary fuel of choice for certain cells such as the neurons, and most other cells utilize glucose as their main source of energy in the form of adenosine triphosphate (ATP). Clinical signs of hypoglycemia occur relatively late when there is failure to generate enough ATP for adequate cellular function. This may be due to not only hypoglycemia but also deficiency of alternative fuels or inability to break down stored energy sources. Because it is difficult to measure available alternative fuels for ATP generation clinically, the availability of fuel source is estimated by the blood levels of glucose, a surrogate molecule.
During gestation, there is a reliable transfer of maternal glucose to the fetus, and the fetus utilizes the minimum amount of energy for its own metabolism and stores the transported glucose in the form of glycogen and fat. This in utero physiologic state is interrupted at birth, and the neonate’s metabolic needs increase substantially after birth. Thus there is an initial drop in glucose, followed by a slow and steady rise in its blood glucose to the acceptable normal range. For these reasons, coming up with a definition of hypoglycemia in the neonate has been a challenge, since blood sugar fluctuations are common in the first several hours after birth. The American Academy of Pediatrics (AAP) and the Pediatric Endocrine Society (PES) have both tried to come to a consensus for a safe range of glucose in neonates. It is now accepted that plasma glucose values drop down to 30 mg/dL (1.67 mmol/L) in the first 2 hours of life and subsequently rise to a value of at least 45 mg/dL (2.5 mmol/L) before stabilizing at around 12−24 hours. The AAP defines hypoglycemia as a numerical plasma glucose value of less than 47 mg/dL (2.6 mmol/L) in ...