title: Brain tissue oxygenation, lactate-pyruvate ratio, and cerebrovascular pressure reactivity monitoring in severe traumatic brain injury: systematic review and viewpoint.
abstract: BACKGROUND
  Prevention and detection of secondary brain insults via multimodality neuromonitoring is a major goal in patients with severe traumatic brain injury (TBI).
  
  
  OBJECTIVE
  Explore the underlying pathophysiology and clinical outcome correlates as it pertains to combined monitoring of ≥2 from the following variables: partial brain tissue oxygen tension (PbtO(2)), pressure reactivity index (PRx), and lactate pyruvate ratio (LPR).
  
  
  METHODS
  Data sources included Medline, EMBASE, and evidence-based databases (Cochrane DSR, ACP Journal Club, DARE, and the Cochrane Controlled Trials Register). The PRISMA recommendations were followed. Two authors independently selected articles meeting inclusion criteria. Studies enrolled adults who required critical care and monitoring in the setting of TBI. Included studies reported on correlations between the monitored variables and/or reported on correlations of the variables with clinical outcomes.
  
  
  RESULTS
  Thirty-four reports were included (32 observational studies and 2 randomized controlled trials) with a mean sample size of 34 patients (range 6-223), and a total of 1,161 patient-observations. Overall methodological quality was moderate. Due to inter-study heterogeneity in outcomes of interest, study design, and in both number and type of covariates included in multivariable analyses, quantitative synthesis of study results was not undertaken.
  
  
  CONCLUSIONS
  Several literature limitations were identified including small number of subjects, lack of clinical outcome correlations, inconsistent probe location, and overall moderate quality among the included studies. These limitations preclude any firm conclusions; nevertheless we suggest that the status of cerebrovascular reactivity is not only important for cerebral perfusion pressure optimization but should also inform interpretation and interventions targeted on PbtO(2) and LPR. Assessment of reactivity can be the first step in approaching the relations among cerebral blood flow, oxygen delivery, demand, and cellular metabolism.
authors.affiliation: Division of Neurocritical Care, Department of Neurology, Baylor College of Medicine, 6501 Fannin Street, MS: NB 320, Houston, TX, 77030, USA, lazaridi@bcm.edu.
authors.forename: Christos
authors.initials: C
authors.lastname: Lazaridis
authors.forename: Charles M
authors.initials: CM
authors.lastname: Andrews
mesh_terms: D062186:Arterial Pressure / Q000502:physiology*; D001930:Brain Injuries / Q000175:diagnosis* / Q000378:metabolism / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism*; D008991:Monitoring, Physiologic / Q000379:methods*; D010101:Oxygen Consumption / Q000502:physiology*; D019289:Pyruvic Acid / Q000378:metabolism*
chemical_list: D019344:Lactic Acid; D019289:Pyruvic Acid