title: Microdialysis Monitoring of CSF Parameters in Severe Traumatic Brain Injury Patients: A Novel Approach.
abstract: BACKGROUND
  Neuro-intensive care following traumatic brain injury (TBI) is focused on preventing secondary insults that may lead to irreversible brain damage. Microdialysis (MD) is used to detect deranged cerebral metabolism. The clinical usefulness of the MD is dependent on the regional localization of the MD catheter. The aim of this study was to analyze a new method of continuous cerebrospinal fluid (CSF) monitoring using the MD technique. The method was validated using conventional laboratory analysis of CSF samples. MD-CSF and regional MD-Brain samples were correlated to patient outcome.
  
  
  METHODS
  A total of 14 patients suffering from severe TBI were analyzed. They were monitored using (1) a MD catheter (CMA64-iView, n = 7448 MD samples) located in a CSF-pump connected to the ventricular drain and (2) an intraparenchymal MD catheter (CMA70, n = 8358 MD samples). CSF-lactate and CSF-glucose levels were monitored and were compared to MD-CSF samples. MD-CSF and MD-Brain parameters were correlated to favorable (Glasgow Outcome Score extended, GOSe 6-8) and unfavorable (GOSe 1-5) outcome.
  
  
  RESULTS
  Levels of glucose and lactate acquired with the CSF-MD technique could be correlated to conventional levels. The median MD recovery using the CMA64 catheter in CSF was 0.98 and 0.97 for glucose and lactate, respectively. Median MD-CSF (CMA 64) lactate (p = 0.0057) and pyruvate (p = 0.0011) levels were significantly lower in the favorable outcome group compared to the unfavorable group. No significant difference in outcome was found using the lactate:pyruvate ratio (LPR), or any of the regional MD-Brain monitoring in our analyzed cohort.
  
  
  CONCLUSIONS
  This new technique of global MD-CSF monitoring correlates with conventional CSF levels of glucose and lactate, and the MD recovery is higher than previously described. Increase in lactate and pyruvate, without any effect on the LPR, correlates to unfavorable outcome, perhaps related to the presence of erythrocytes in the CSF.
authors.affiliation: Section for Neurosurgery, Department of Clinical Neuroscience, Karolinska Institutet, Karolinska University Hospital Solna , Stockholm , Sweden.
authors.forename: Eric P
authors.initials: EP
authors.lastname: Thelin
authors.affiliation: Section of Anesthesiology and Intensive Care, Department of Physiology and Pharmacology, Karolinska Institutet , Stockholm , Sweden.
authors.forename: David W
authors.initials: DW
authors.lastname: Nelson
authors.affiliation: Department of Clinical Neuroscience, Karolinska Institutet , Stockholm , Sweden.
authors.forename: Per Hamid
authors.initials: PH
authors.lastname: Ghatan
authors.affiliation: Section for Neurosurgery, Department of Clinical Neuroscience, Karolinska Institutet, Karolinska University Hospital Solna , Stockholm , Sweden.
authors.forename: Bo-Michael
authors.initials: BM
authors.lastname: Bellander
keywords: TBI; cerebrospinal fluid; lactate; microdialysis; outcome; pyruvate