Cerebral Microdialysis Monitoring of Energy Metabolism: Relation to Cerebral Blood Flow and Oxygen Delivery in Aneurysmal Subarachnoid Hemorrhage.

Introduction: In this study, we investigated the roles of cerebral blood flow (CBF) and cerebral oxygen delivery (CDO 2 ) in relation to cerebral energy metabolism after aneurysmal subarachnoid hemorrhage (aSAH).

Methods: Fifty-seven adult aSAH patients treated on the neurointensive care unit at Uppsala, Sweden between 2012 and 2020, with at least 1 xenon-enhanced computed tomography (Xe-CT) scan in the first 14 days after ictus and concurrent microdialysis (MD) monitoring, were included in this retrospective study. CBF was measured globally and focally (around the MD catheter) with Xe-CT, and CDO 2 calculated. Cerebral energy metabolites were measured using MD.

Results: Focal ischemia (CBF <20 mL/100 g/min around the MD catheter was associated with lower median [interquartile range]) MD-glucose (1.2 [0.7 to 2.2] mM vs. 2.3 [1.3 to 3.5] mM; P =0.05) and higher MD-lactate-pyruvate (LPR) ratio (34 [29 to 66] vs. 25 [21 to 32]; P =0.02). A compensated/normal MD pattern (MD-LPR <25) was observed in the majority of patients (22/23, 96%) without focal ischemia, whereas 4 of 11 (36%) patients with a MD pattern of poor substrate supply (MD-LPR >25, MD-pyruvate <120 µM) had focal ischemia as did 5 of 20 (25%) patients with a pattern of mitochondrial dysfunction (MD-LPR >25, MD-pyruvate >120 µM) ( P =0.04). Global CBF and CDO 2 , and focal CDO 2 , were not associated with the MD variables.

Conclusions: While MD is a feasible tool to study cerebral energy metabolism, its validity is limited to a focal area around the MD catheter. Cerebral energy disturbances were more related to low CBF than to low CDO 2 . Considering the high rate of mitochondrial dysfunction, treatments that increase CBF but not CDO 2 , such as hemodilution, may still benefit glucose delivery to drive anaerobic metabolism.