title: Improving the recovery of S100B protein in cerebral microdialysis: implications for multimodal monitoring in neurocritical care.
abstract: BACKGROUND
  Cerebral microdialysis is an established research tool that is used by an increasing number of neurocritical care units as a component of bedside multimodality monitoring. Body fluid biomarkers are an emerging tool for the assessment of brain injury. The correct interpretation of body fluid biomarker levels depends on the degree of recovery, i.e. relative recovery and the accuracy of the analytical technique.
  
  
  METHODS
  In vitro recovery experiments were performed on 100mL volumes of cerebrospinal fluid and solutions of S100B, glucose, lactate and pyruvate comparing relative recoveries using commercially available 20 kDa (CMA70) and 100 kDa (CMA71) microdialysis catheters. We also compared the CMA 600 microdialysis analyzer with a YSI 2003 STAT Plus analyzer for glucose and lactate to determine its reliability.
  
  
  RESULTS
  Significantly, we demonstrate the improved recovery of the protein S100B using a larger molecular weight (MW) cut-off catheter (20 kDa range: 0.1-9%; 100 kDa range: 1.7-18.3%) while maintaining comparable performance for the conventional markers glucose, lactate and pyruvate. Additionally we found that the CMA 600 analyzer may be prone to overestimation of lactate readings at higher concentration with implications for clinical decision-making.
  
  
  CONCLUSIONS
  Our data demonstrates that the 100 kDa MW cut-off catheter allows for the improved recovery of macromolecules in cerebral microdialysis research while maintaining the value of existing MD data for routine clinical use.
authors.affiliation: Department of Neurosurgery, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N3BG, UK. R.Afinowi@ion.ucl.ac.uk
authors.forename: R
authors.initials: R
authors.lastname: Afinowi
authors.forename: M
authors.initials: M
authors.lastname: Tisdall
authors.forename: G
authors.initials: G
authors.lastname: Keir
authors.forename: M
authors.initials: M
authors.lastname: Smith
authors.forename: N
authors.initials: N
authors.lastname: Kitchen
authors.forename: A
authors.initials: A
authors.lastname: Petzold
mesh_terms: D001930:Brain Injuries / Q000175:diagnosis / Q000378:metabolism*; D002404:Catheterization / Q000379:methods; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D045604:Extracellular Fluid / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D019344:Lactic Acid / Q000378:metabolism; D017551:Microdialysis / Q000379:methods*; D008991:Monitoring, Physiologic / Q000379:methods*; D009414:Nerve Growth Factors / Q000378:metabolism*; D019289:Pyruvic Acid / Q000378:metabolism; D020127:Recovery of Function / Q000502:physiology*; D015203:Reproducibility of Results; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000378:metabolism*
chemical_list: D009414:Nerve Growth Factors; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; C579160:S100B protein, human; D019344:Lactic Acid; D019289:Pyruvic Acid; D005947:Glucose