Impact of Intraoperative Hyperglycemia on Brain Structures and Volumes.

Abstract

In hyperglycemic patients, who succumbed to septic shock, an increased rate of apoptosis of microglial cells and damaged neurons of the hippocampus were found. However, the influence of perioperative glucose levels on hippocampal brain structures has not yet been investigated. As part of the ongoing BIOCOG project, a subgroup of N=65 elderly nondemented patients were analyzed who underwent elective surgery of ≥60minutes. In these patients, at least one intraoperative blood glucose (BG) measurement was available from the medical charts. Intraoperative glucose maximum was determined in each patient. Preoperatively and at 3 months follow-up, structural neuroimaging was performed with T1-weighted magnetization prepared rapid gradient-echo sequence (MP-Rage) and a dedicated high-resolution hippocampus magnetic resonance imaging (MRI). The MRI scans were analyzed to assess pre- or postoperative volume changes of the hippocampus as a whole and hippocampal subfields. We also assessed changes of frontal lobe volume and cortical thickness. Overall, 173 intraoperative BG levels were obtained in 65 patients (median 2 per patient). A total of 18 patients showed intraoperative hyperglycemia (glucose maximum≥150 mg/dL). Controlling for age and diabetes status, no significant impact of intraoperative hyperglycemia was found on the pre-post volume change of the hippocampus as a whole, hippocampal subfields, frontal lobe, and frontal cortical thickness. This study found no effect of intraoperative hyperglycemia on postoperative brain structures and volumes including volumes of hippocampus and hippocampal subfields, frontal lobe, and frontal cortical thickness. Further studies investigating the impact of intraoperatively elevated glucose levels should consider a tighter or even continuous glycemic measurement and the determination of central microglial activation.