Catecholamine Excretion in Spontaneously Occurring Asymptomatic Neonatal Hypoglycemia

Abstract

ExtractTwenty-six full-term infants delivered vaginally were studied. There were 16 males and 10 females. Capillary blood samples for glucose were obtained hourly. When the infant voided spontaneously, the urine collection for determination of epinephrine (E), norepinephrine (NE), metanephrine (M), normetanephrine (NM), and vanillylmandelic acid (VMA) was discontinued. Using the value of 30 mg/100 ml as the lower limit of normal for glucose in blood, the study patients were divided into three groups: group A (16 subjects), all values over 30 mg/100 ml; group B (5 subjects), one value under 30 mg/100 ml; group G (5 subjects), two or more values less than 30 mg/100 ml.Comparison of the means by groups revealed no significant differences in individual or total catecholamine excretions. The two patients who were judged to be the most severely hypoglycemic, however, showed the lowest epinephrine excretions of the entire study group. Nonparametric statistical analysis was used to compare the epinephrine excretion of the 16 patients who maintained a normal glucose level with that of the 10 patients of groups B and C. A P value of less than 0.05 was obtained, suggesting that the ability to maintain adequate blood glucose was associated with a higher epinephrine excretion. Nonparametric statistical analyses did not show a significant difference in E+M or E +M+VMA excretion among the study groups. This negative finding does not support our hypothesis of deficient epinephrine release as a contributory factor in spontaneous neonatal hypoglycemia.Catecholamines in urine were determined in nine newborns who were treated in a fashion similar to the study groups except that they were not subjected to heel punctures as repeated unpleasant stimuli. The results, expressed as mean±SD were: E, 7.73±5.36; NE, 35.3±22.9; M, 52.8±33.9; NM, 201 ±140; and VMA, 899±356 ng/kg/h. The only significant difference between these values and those of the study group lay in the levels of epinephrine excretion where significant differences were found between these subjects and those in group A. It appears reasonable to attribute the observed difference to the lack of stimulation by heel punctures.A rise in blood glucose concentrations was observed after epinephrine injection in all groups, with no differences between them. SpeculationThese results suggest that in certain instances failure of endogenous epinephrine release may play a role in spontaneous hypoglycemia of the newborn. A major unresolved question is whether this failure of epinephrine release is itself primary, or whether asymptomatic hypoglycemia is not a sufficient stimulus for adrenal activation in these children.

Adrenal Catecholamines Content in Fetal and Newborn Rats

“…In the newborn infant, spontaneously occurring asymptomatic hy poglycemia [17] or severe hypoglycemia in infant of diabetic mothers [18] were not associated with a rise in urinary epinephrine levels. In contrast, it has been shown that newborn infants are capable of responding to insulin-in duced hypoglycemia with increased urinary epinephrine secretion (11).…”