Autoradiographic determination of regional cerebral blood flow during hypoglycemia in newborn dogs.

To ascertain the regional cerebral blood flow (CBF) responses to hypoglycemia, nine newborn dogs were treated with insulin to blood glucose concentrations ranging from 1 to 35 mg/dl (mean 22 mg/dl). Systemic physiologic monitoring revealed no differences in mean arterial blood pressure, heart rate, paO2, paCO2, pHa, or blood lactate in the hypoglycemis animals and five normoglycemic controls. Significant increases in CBF occurred in 17 of 20 analyzed structures of brain in the hypoglycemic puppies, ranging from 158 to 446% of the normoglyycemic values. The percent increases in CBF were greatest in brainstem structures compared to other major regions of brain. A positive correlation existed between mean arterial blood pressure and cerebral cortical blood flow, suggesting a loss of CBF autoregulation during hypoglycemia. The pathophysiologic mechanism for the elevations in regional CBF might relate to stimulation of beta-adrenergic receptors in brain, as has been shown in adults.