Cerebral blood flow in type II diabetes mellitus patients with impaired awareness of hypoglycemia: a cross-sectional study

Cerebral blood flow is maintained and regulated through various homeostatic mechanisms. It is maintained even during hypoglycemia in patients with type 1 diabetes mellitus, but appears to increase in those with impaired awareness of hypoglycemia. However, experiments are lacking to clarify these findings. Thus, this study was conducted to investigate whether cerebral blood flow increases in type 2 diabetes mellitus patients with impaired awareness of hypoglycemia by using Doppler sonography. This was a cross-sectional study conducted from July 2021 to June 2022 in the emergency department (ED) of Inje University Busan Paik Hospital, Busan, South Korea. Patients with type 2 diabetes with complaints of various symptoms of hypoglycemia (defined as blood glucose level <60 mg/dL) were evaluated for this study after obtaining their informed consent. First, we assessed each patient's awareness of hypoglycemia using the Gold method. Cerebral blood flow was then measured on Doppler sonography. The primary outcome was blood flow in both internal carotid arteries, and secondary outcomes included the diameter and time-averaged maximum velocity of both internal carotid arteries. A total of 132 patients were enrolled in the study, but 11 patients were excluded from analysis. Hypoglycemia was associated with increased cerebral blood flow in those with impaired awareness of hypoglycemia, but this association was not observed in other groups. The blood flow in the left internal carotid artery was significantly higher compared to the right side, perhaps due to the anatomical differences between the two arteries. The increased cerebral blood flow could be due to an adaptive response to hypoglycemia to enhance nutrient supply to the brain. However, given that this was a cross-sectional study, causality could not be determined. Thus, as in type 1 diabetes mellitus, hypoglycemia is associated with an increased cerebral blood flow in type 2 diabetes mellitus as well.