title: Potential non-hypoxic/ischemic causes of increased cerebral interstitial fluid lactate/pyruvate ratio: a review of available literature.
abstract: Microdialysis, an in vivo technique that permits collection and analysis of small molecular weight substances from the interstitial space, was developed more than 30 years ago and introduced into the clinical neurosciences in the 1990s. Today cerebral microdialysis is an established, commercially available clinical tool that is focused primarily on markers of cerebral energy metabolism (glucose, lactate, and pyruvate) and cell damage (glycerol), and neurotransmitters (glutamate). Although the brain comprises only 2% of body weight, it consumes 20% of total body energy. Consequently, the ability to monitor cerebral metabolism can provide significant insights during clinical care. Measurements of lactate, pyruvate, and glucose give information about the comparative contributions of aerobic and anaerobic metabolisms to brain energy. The lactate/pyruvate ratio reflects cytoplasmic redox state and thus provides information about tissue oxygenation. An elevated lactate pyruvate ratio (>40) frequently is interpreted as a sign of cerebral hypoxia or ischemia. However, several other factors may contribute to an elevated LPR. This article reviews potential non-hypoxic/ischemic causes of an increased LPR.
authors.affiliation: University of Pennsylvania School of Medicine, Philadelphia, PA, USA. dlarach@med.upenn.edu
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Larach
authors.forename: W Andrew
authors.initials: WA
authors.lastname: Kofke
authors.forename: Peter
authors.initials: P
authors.lastname: Le Roux
mesh_terms: D000332:Aerobiosis / Q000502:physiology; D000693:Anaerobiosis / Q000502:physiology; D001786:Blood Glucose / Q000378:metabolism; D001921:Brain / Q000098:blood supply / Q000503:physiopathology*; D001930:Brain Injuries / Q000175:diagnosis* / Q000503:physiopathology*; D003422:Critical Care / Q000379:methods*; D004734:Energy Metabolism / Q000502:physiology*; D045604:Extracellular Fluid / Q000502:physiology*; D018698:Glutamic Acid / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D006801:Humans; D020925:Hypoxia-Ischemia, Brain / Q000175:diagnosis* / Q000503:physiopathology*; D019344:Lactic Acid / Q000378:metabolism*; D017551:Microdialysis; D008991:Monitoring, Physiologic / Q000379:methods*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000502:physiology; D019289:Pyruvic Acid / Q000378:metabolism*; D012039:Regional Blood Flow / Q000502:physiology
chemical_list: D001786:Blood Glucose; D019344:Lactic Acid; D018698:Glutamic Acid; D019289:Pyruvic Acid; D005990:Glycerol; D010100:Oxygen