Capillary recruitment for preservation of cerebral glucose influx in hypoglycemic, preterm newborns: evidence for a glucose sensor?

Abstract

Changes in cerebral blood volume (CBV) were investigated by means of near-infrared spectroscopy in 18 preterm newborns during treatment with intravenous bolus glucose. All newborns were breathing spontaneously, and their postnatal age was 2 hours. Blood glucose concentration ranged between 0.3 and 2.2 mmol/L. Cerebral blood volume began to decrease shortly after the glucose infusion was terminated, and steady state was obtained after approximately 3 minutes. The decrease in CBV averaged 0.15 mL/100 g (range 0.02 to 0.40 mL/100 g). Thereafter, CBV remained constant. Individual reductions in CBV were inversely related to the pretreatment concentration of glucose, whereas there was no relation between changes in CBV and alterations in blood gas values or in mean arterial blood pressure. It is suggested that previously unperfused capillaries are recruited to maintain the glucose transport into neurons of hypoglycemic, preterm newborns. The rapidity whereby vessels adjust to alterations in glucose levels indicates the existence of a cerebral glucose sensor.