title: Relevance of intracranial hypertension for cerebral metabolism in aneurysmal subarachnoid hemorrhage. Clinical article.
abstract: OBJECTIVE
  Intracranial hypertension, defined as intracranial pressure (ICP) >/= 20 mm Hg, is a complication typically associated with head injury. Its impact on cerebral metabolism, ICP therapy, and outcome has rarely been studied in patients with aneurysmal subarachnoid hemorrhage (aSAH); such an assessment is the authors' goal in the present study.
  
  
  METHODS
  Cerebral metabolism was prospectively studied in 182 patients with aSAH. The database was retrospectively analyzed with respect to ICP. Patients were classified into 2 groups based on ICP. There were 164 with low ICP (<20 mm Hg) and 18 with high ICP (>or=20 mm Hg, measured>6 hours/day). Cerebral microdialysis parameters of energy metabolism, glycerol, and glutamate levels were analyzed hourly from the brain parenchyma of interest for 7 days. The 12-month outcome in these patients was evaluated.
  
  
  RESULTS
  In the high ICP group, extended ICP therapy including decompressive craniectomy was necessary in 7 patients (39%). Cerebral glycerol levels and the lactate/pyruvate ratio were pathologically increased on Days 1-7 after aSAH (p<0.001). The excitotoxic neurotransmitter glutamate and glycerol, a marker of membrane degradation, further increased on Days 5-7, probably reflecting the development of secondary brain damage. An ICP>or=20 mm Hg was shown to have a significant influence on the 12-month Glasgow Outcome Scale (GOS) score (p=0.001) and was a strong predictor of mortality (OR=24.6; p<0.001). Glutamate (p=0.012), the lactate/pyruvate ratio as a marker of anaerobic metabolism (p=0.028), age (p<0.001), and Fisher grade (p=0.001) also influenced the GOS score at 12 months.
  
  
  CONCLUSIONS
  The authors confirmed the relevance of intracranial hypertension as a severe complication in patients with aSAH. Because high ICP is associated with a severely deranged cerebral metabolism and poor outcome, future studies focusing on metabolism-guided, optimized ICP therapy could help minimize secondary brain damage and improve prognosis in patients with aSAH.
authors.affiliation: Department of Neurosurgery, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Nagel
authors.forename: Daniela
authors.initials: D
authors.lastname: Graetz
authors.forename: Tania
authors.initials: T
authors.lastname: Schink
authors.forename: Katja
authors.initials: K
authors.lastname: Frieler
authors.forename: Oliver
authors.initials: O
authors.lastname: Sakowitz
authors.forename: Peter
authors.initials: P
authors.lastname: Vajkoczy
authors.forename: Asita
authors.initials: A
authors.lastname: Sarrafzadeh
mesh_terms: D000328:Adult; D001921:Brain / Q000378:metabolism*; D001927:Brain Diseases / Q000378:metabolism* / Q000401:mortality; D003399:Craniotomy; D019299:Decompression, Surgical; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D006801:Humans; D019586:Intracranial Hypertension / Q000378:metabolism* / Q000401:mortality* / Q000601:surgery; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D017551:Microdialysis; D008875:Middle Aged; D019095:Point-of-Care Systems; D011379:Prognosis; D011446:Prospective Studies; D019289:Pyruvic Acid / Q000378:metabolism; D012189:Retrospective Studies; D013345:Subarachnoid Hemorrhage / Q000378:metabolism* / Q000401:mortality* / Q000601:surgery; D016896:Treatment Outcome
chemical_list: D019344:Lactic Acid; D018698:Glutamic Acid; D019289:Pyruvic Acid; D005990:Glycerol