Glucose and Lactate Concentrations in Plasma, Cerebrospinal Fluid, and Brain Parenchyma Following Aneurysmal...

Patients with aneurysmal subarachnoid hemorrhage (aSAH) are at high risk of secondary ischemia, and timely insight into cerebral metabolism may improve clinical management. Cerebral microdialysis offers continuous metabolic monitoring but is invasive, focal, and confined to specialized centers. Peripheral blood and cerebrospinal fluid (CSF) could provide less invasive, more accessible surrogates for assessing cerebral metabolic status. This study aimed to evaluate glucose and lactate dynamics across blood, CSF, and brain parenchyma in patients with severe aSAH.

A total of 39 patients with aSAH undergoing multimodal neuromonitoring were retrospectively analyzed. Glucose and lactate levels from plasma, CSF, and cerebral microdialysis were matched within 90-min intervals relative to each microdialysis measurement. Associations were analyzed using linear mixed-effects models.

Plasma (p < 0.001) and CSF (p < 0.001) glucose levels were significantly associated with cerebral glucose concentrations. Moderate correlations were observed between plasma-brain (r = 0.54) and plasma-CSF (r = 0.55), while CSF-brain correlation was weaker (r = 0.36). For lactate, significant associations were found between CSF and brain (p = 0.04; r = 0.24) and between plasma and CSF (p < 0.001; r = 0.33), but plasma-brain lactate showed no significant relationship. The plasma-brain glucose association weakened slightly over time (p = 0.008) and strengthened during episodes of low brain tissue oxygenation (pbtO₂ < 15 mm Hg; p = 0.01). Insulin had no effect on glucose relationships but significantly attenuated the plasma-brain lactate association (p < 0.001). The presence of metabolic crisis (lactate/pyruvate ratio > 40) strengthened the CSF-brain lactate association (p = 0.04). CSF cell count had no significant effect.

In severe aSAH, glucose and lactate levels in blood and CSF reflect cerebral values in a compartment- and metabolite-specific manner, but with high variability influenced by clinical conditions. These findings suggest that blood and CSF provide only limited information about cerebral metabolism, highlighting the complementary value of cerebral microdialysis for individualized, brain-targeted monitoring.