title: Bedside microdialysis reflects dysfunction of cerebral energy metabolism in patients with aneurysmal subarachnoid hemorrhage as confirmed by 15 O-H2 O-PET and 18 F-FDG-PET.
abstract: OBJECTIVE
  To compare microdialysis (MD) and positron emission tomography (PET) in the detection of ischemia in aneurysmal subarachnoid hemorrhage (SAH) patients.
  
  
  METHODS
  15 SAH patients (13F/2M, 48+/-13 years, WFNS Grade I-V) were prospectively included in the study. A MD-catheter was inserted into the brain parenchyma most likely to be affected by vasospasm directly after aneurysm clipping. Glucose, pyruvate, lactate, glutamate and glycerol were analyzed hourly (CMA 600). 15O-H2O-PET scans (n=10) and 18F-FDG-PET scans (n=13) were performed between the day 2 and 17 after SAH. 15O-H2O-PET data were merged with CT scans to provide quantification of rCBF within the MD-ROI (rCBFMD; Amira, ZIB Berlin, Germany). 18F-FDG-PET data were evaluated visually by visual analysis.
  
  
  RESULTS
  Regions of glucose hypometabolism were observed in 10 patients with symptoms of ischemia. Their rCBF was lower compared to asymptomatic patients (p<0.05). The MD levels of glutamate, lactate, the L/P ratio and glycerol were significantly higher in symptomatic than asymptomatic patients (p<0.05). Out of all measured MD parameters, glutamate showed the closest correlation with rCBF (r=-0.66, p=0.014). Microdialysis parameters were well correlated with glucose hypometabolism (18F-FDG-PET) and symptoms of ischemia. However, the threshold for a metabolic derangement was above the limits of cerebral ischemia defined by PET.
  
  
  CONCLUSIONS
  MD is a useful tool to monitor ischemia, especially in patients with high-grade SAH.
authors.affiliation: Department of Neurosurgery, Charité Campus Virchow Medical Clinic, Humboldt University of Berlin, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Sarrafzadeh
authors.forename: D
authors.initials: D
authors.lastname: Haux
authors.forename: M
authors.initials: M
authors.lastname: Plotkin
authors.forename: L
authors.initials: L
authors.lastname: Lüdemann
authors.forename: H
authors.initials: H
authors.lastname: Amthauer
authors.forename: A
authors.initials: A
authors.lastname: Unterberg
mesh_terms: D000328:Adult; D000368:Aged; D002560:Cerebrovascular Circulation / Q000502:physiology*; D019788:Fluorodeoxyglucose F18; D006801:Humans; D017551:Microdialysis; D008875:Middle Aged; D010104:Oxygen Radioisotopes; D019095:Point-of-Care Systems; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D013345:Subarachnoid Hemorrhage / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000503:physiopathology*
chemical_list: D010104:Oxygen Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18