title: Time course of recovery from cerebral vulnerability after severe traumatic brain injury: a microdialysis study.
abstract: BACKGROUND
  The aim of this study was to evaluate the time course of recovery from cerebral vulnerability, using microdialysis (MD) technique and cerebral vascular autoregulation measurement, to clarify the appropriate timing of subsequent major surgical procedures, and to minimize the possibility of secondary brain injury in patients with severe traumatic brain injury (STBI).
  
  
  METHODS
  In 3,470 MD samples of 25 patients with STBI, cerebral extracellular biomarkers (glucose, lactate, pyruvate, glycerol, and glutamate) were measured. In addition, to estimate cerebral vascular autoregulaton, the pressure reactivity index (PRx) was calculated with intracranial pressure (ICP) and mean arterial pressure. The data with ICP, cerebral perfusion pressure (CPP), and PRx were collected hourly for 7 days after injury and they were compared with MD biomarkers daily.
  
  
  RESULTS
  During the study period, the average ICP and CPP remained stable and were within the threshold of STBI treatment guidelines. After injury, the extracellular glucose concentration decreased, and the levels of glycerol, glutamate, and lactate/pyruvate ratio (LPR), which indicate cerebral ischemia and neural cell damage, increased. On the fourth day after injury, the extracellular glucose concentration improved, and the value of LPR decreased. The average PRx decreased daily and became negative on the fifth day after injury.
  
  
  CONCLUSIONS
  Our results indicated that cerebral vascular autoregulation would recover on the fourth day after STBI, and cerebral perfusion might be increased by recovery of autoregulation. Thus, subsequent nonemergent surgery should be performed at least 4 days after STBI to prevent secondary brain injury. In addition, we should keep in mind that the cerebral vulnerability might persist for 4 days after suffering STBI.
authors.affiliation: Department of Emergency and Critical Care Medicine, Nippon Medical School, Tokyo, Japan. SYokobori@med.miami.edu
authors.forename: Shoji
authors.initials: S
authors.lastname: Yokobori
authors.forename: Akihiro
authors.initials: A
authors.lastname: Watanabe
authors.forename: Gaku
authors.initials: G
authors.lastname: Matsumoto
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Onda
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Masuno
authors.forename: Akira
authors.initials: A
authors.lastname: Fuse
authors.forename: Shigeki
authors.initials: S
authors.lastname: Kushimoto
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yokota
mesh_terms: D000704:Analysis of Variance; D015415:Biomarkers / Q000378:metabolism; D001831:Body Temperature; D001930:Brain Injuries / Q000378:metabolism* / Q000401:mortality; D045604:Extracellular Fluid / Q000737:chemistry; D005260:Female; D015600:Glasgow Coma Scale; D005947:Glucose / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D006801:Humans; D007427:Intracranial Pressure; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D017551:Microdialysis; D019289:Pyruvic Acid / Q000378:metabolism; D013997:Time Factors
chemical_list: D015415:Biomarkers; D019344:Lactic Acid; D018698:Glutamic Acid; D019289:Pyruvic Acid; D005947:Glucose; D005990:Glycerol