title: Lactate and the lactate-to-pyruvate molar ratio cannot be used as independent biomarkers for monitoring brain energetic metabolism: a microdialysis study in patients with traumatic brain injuries.
abstract: BACKGROUND
  For decades, lactate has been considered an excellent biomarker for oxygen limitation and therefore of organ ischemia. The aim of the present study was to evaluate the frequency of increased brain lactate levels and the LP ratio (LPR) in a cohort of patients with severe or moderate traumatic brain injury (TBI) subjected to brain microdialysis monitoring to analyze the agreement between these two biomarkers and to indicate brain energy metabolism dysfunction.
  
  
  METHODS
  Forty-six patients with an admission Glasgow coma scale score of ≤13 after resuscitation admitted to a dedicated 10-bed Neurotraumatology Intensive Care Unit were included, and 5305 verified samples of good microdialysis data were analyzed.
  
  
  RESULTS
  Lactate levels were above 2.5 mmol/L in 56.9% of the samples. The relationships between lactate and the LPR could not be adequately modeled by any linear or non-linear model. Neither Cohen's kappa nor Gwet's statistic showed an acceptable agreement between both biomarkers to classify the samples in regard to normal or abnormal metabolism. The dataset was divided into four patterns defined by the lactate concentrations and the LPR. A potential interpretation for these patterns is suggested and discussed. Pattern 4 (low pyruvate levels) was found in 10.7% of the samples and was characterized by a significantly low concentration of brain glucose compared with the other groups.
  
  
  CONCLUSIONS
  Our study shows that metabolic abnormalities are frequent in the macroscopically normal brain in patients with traumatic brain injuries and a very poor agreement between lactate and the LPR when classifying metabolism. The concentration of lactate in the dialysates must be interpreted while taking into consideration the LPR to distinguish between anaerobic metabolism and aerobic hyperglycolysis.
authors.affiliation: Department of Neurosurgery, Vall d'Hebron University Hospital, Universidad Autonoma de Barcelona, Barcelona, Spain; Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Universidad Autonoma de Barcelona, Barcelona, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Sahuquillo
authors.affiliation: Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Universidad Autonoma de Barcelona, Barcelona, Spain.
authors.forename: Maria-Angels
authors.initials: MA
authors.lastname: Merino
authors.affiliation: Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Universidad Autonoma de Barcelona, Barcelona, Spain.
authors.forename: Angela
authors.initials: A
authors.lastname: Sánchez-Guerrero
authors.affiliation: Department of Neurosurgery, Vall d'Hebron University Hospital, Universidad Autonoma de Barcelona, Barcelona, Spain; Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Universidad Autonoma de Barcelona, Barcelona, Spain.
authors.forename: Fuat
authors.initials: F
authors.lastname: Arikan
authors.affiliation: Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Universidad Autonoma de Barcelona, Barcelona, Spain.
authors.forename: Marian
authors.initials: M
authors.lastname: Vidal-Jorge
authors.affiliation: Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Universidad Autonoma de Barcelona, Barcelona, Spain.
authors.forename: Tamara
authors.initials: T
authors.lastname: Martínez-Valverde
authors.affiliation: Neurotraumatology Intensive Care Unit, Vall d'Hebron University Hospital, Universidad Autonoma de Barcelona, Barcelona, Spain.
authors.forename: Anna
authors.initials: A
authors.lastname: Rey
authors.affiliation: Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Universidad Autonoma de Barcelona, Barcelona, Spain; Neurotraumatology Intensive Care Unit, Vall d'Hebron University Hospital, Universidad Autonoma de Barcelona, Barcelona, Spain.
authors.forename: Marilyn
authors.initials: M
authors.lastname: Riveiro
authors.affiliation: Department of Neurosurgery, Vall d'Hebron University Hospital, Universidad Autonoma de Barcelona, Barcelona, Spain; Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Universidad Autonoma de Barcelona, Barcelona, Spain.
authors.forename: Maria-Antonia
authors.initials: MA
authors.lastname: Poca
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D001930:Brain Injuries / Q000378:metabolism*; D004734:Energy Metabolism; D005260:Female; D005947:Glucose / Q000378:metabolism; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D019289:Pyruvic Acid / Q000378:metabolism*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D019344:Lactic Acid; D019289:Pyruvic Acid; D005947:Glucose