title: Cerebral energy metabolism during mitochondrial dysfunction induced by cyanide in piglets.
abstract: BACKGROUND
  Mitochondrial dysfunction is an important factor contributing to tissue damage in both severe traumatic brain injury and ischemic stroke. This experimental study explores the possibility to diagnose the condition bedside by utilising intracerebral microdialysis and analysis of chemical variables related to energy metabolism.
  
  
  METHODS
  Mitochondrial dysfunction was induced in piglets and evaluated by monitoring brain tissue oxygen tension (PbtO2 ) and cerebral levels of glucose, lactate, pyruvate, glutamate, and glycerol bilaterally. The biochemical variables were obtained by microdialysis and immediate enzymatic analysis. Mitochondrial function was blocked by unilateral infusion of NaCN/KCN (0.5 mol/L) through the microdialysis catheter (N = 5). As a reference, NaCl (0.5 mol/L) was infused by intracerebral microdialysis in one group of animals (N = 3).
  
  
  RESULTS
  PbtO2 increased during cyanide infusion and returned to baseline afterwards. The lactate/pyruvate (LP) ratio increased significantly following cyanide infusion because of a marked increase in lactate level while pyruvate remained within normal limits. Glutamate and glycerol increased after cyanide infusion indicating insufficient energy metabolism and degradation of cellular membranes, respectively.
  
  
  CONCLUSIONS
  Mitochondrial dysfunction is characterised by an increased LP ratio signifying a shift in cytoplasmatic redox state at normal or elevated PbtO2 . The condition is biochemically characterised by a marked increase in cerebral lactate with a normal or elevated pyruvate level. The metabolic pattern is different from cerebral ischemia, which is characterised by simultaneous decreases in intracerebral pyruvate and PbtO2 . The study supports the hypothesis that cerebral ischemia and mitochondrial dysfunction may be identified and separated at the bedside by utilising intracerebral microdialysis.
authors.affiliation: Departments of Anaesthesiology and Neurosurgery, Odense University Hospital, Odense C, Denmark. troels.nielsen@ouh.regionsyddanmark.dk
authors.forename: T H
authors.initials: TH
authors.lastname: Nielsen
authors.forename: N V
authors.initials: NV
authors.lastname: Olsen
authors.forename: P
authors.initials: P
authors.lastname: Toft
authors.forename: C H
authors.initials: CH
authors.lastname: Nordström
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D001923:Brain Chemistry; D002245:Carbon Dioxide / Q000097:blood; D003576:Electron Transport Complex IV / Q000037:antagonists & inhibitors; D004734:Energy Metabolism / Q000187:drug effects*; D005260:Female; D005947:Glucose / Q000032:analysis; D018698:Glutamic Acid / Q000032:analysis; D006019:Glycolysis / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007427:Intracranial Pressure / Q000187:drug effects; D007773:Lactates / Q000032:analysis; D017551:Microdialysis; D008928:Mitochondria / Q000187:drug effects*; D010092:Oximetry; D010100:Oxygen / Q000097:blood; D011190:Potassium Cyanide / Q000633:toxicity*; D011773:Pyruvates / Q000032:analysis; D012966:Sodium Cyanide / Q000633:toxicity*; D034421:Sus scrofa; D013552:Swine
chemical_list: D007773:Lactates; D011773:Pyruvates; D002245:Carbon Dioxide; D018698:Glutamic Acid; D003576:Electron Transport Complex IV; D005947:Glucose; D011190:Potassium Cyanide; D012966:Sodium Cyanide; D010100:Oxygen