title: Brain metabolism during a decrease in cerebral perfusion pressure caused by an elevated intracranial pressure in the porcine neocortex.
abstract: BACKGROUND
  Cranial hypertension coincides with a reduction in cerebral blood flow as well as in oxygen delivery and influences outcome. In this study, we monitored changes in energy-related metabolites in the porcine cortex during an increase of intracranial pressure (ICP) and to determine the level at which damage occurs.
  
  
  METHODS
  Male domestic pigs (32-40 kg) were anesthetized, mechanically ventilated, and randomly assigned to either the experimental (n = 6) or control groups (n = 5). A microdialysis probe (CMA 70) was inserted into the cortex to measure extracellular dialysate concentrations of lactate, pyruvate, glucose, glutamate, and glycerol. Every hour an increase of 10 mm Hg in ICP was preformed in the experimental group by infusion of artificial cerebrospinal fluid into the ventricular system of the brain until a maximum ICP of 50 mm Hg was reached.
  
  
  RESULTS
  We demonstrated a significant increase of lactate and glycerol compared with control at ICP values > or =30 mm Hg and cerebral perfusion pressure (CPP) below 50 mm Hg. The increase of ICP to > or =40 mm Hg in conjunction with a reduction in CPP below 40 mm Hg led to a significant increase in the lactate/pyruvate-ratio and glutamate, as well as a decrease of glucose in relation to control.
  
  
  CONCLUSIONS
  Our data strongly suggest that, during a defined ICP increase, lower CPP values may be tolerable until severe damage occurs. Borderline ICP and CPP values of 30 and 40 mm Hg, respectively, could be advised.
authors: Department of Anesthesiology, University Hospital RWTH Aachen, Aachen, Germany. nzoremba@ukaachen.de
authors: Norbert
authors: N
authors: Zoremba
authors: Joerg
authors: J
authors: Schnoor
authors: Michael
authors: M
authors: Berens
authors: Ralf
authors: R
authors: Kuhlen
authors: Rolf
authors: R
authors: Rossaint
mesh_terms: D000818:Animals; D002545:Brain Ischemia / Q000209:etiology* / Q000378:metabolism / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D004195:Disease Models, Animal; D005947:Glucose / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D019586:Intracranial Hypertension / Q000150:complications / Q000378:metabolism* / Q000503:physiopathology; D007427:Intracranial Pressure; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D017551:Microdialysis; D019579:Neocortex / Q000098:blood supply / Q000378:metabolism*; D019289:Pyruvic Acid / Q000378:metabolism; D034421:Sus scrofa; D013997:Time Factors
chemical_list: D019344:Lactic Acid; D018698:Glutamic Acid; D019289:Pyruvic Acid; D005947:Glucose; D005990:Glycerol