title: A microdialysis technique for routine measurement of macromolecules in the injured human brain.
abstract: OBJECTIVE
  To evaluate a new intracerebral microdialysis catheter with a high-cutoff membrane and its potential for the study of macromolecules in the human brain.
  
  
  METHODS
  Paired intracerebral microdialysis catheters were inserted in 10 patients who became comatose after subarachnoid hemorrhage or traumatic brain injury and were then treated in our neurosurgical unit. The only differences from the routine use of microdialysis in our clinic were the length (20 mm) and cutoff properties of the catheter membranes (100 kD) and the perfusion fluids used (standard perfusion fluid, 3.5% albumin, or Ringer-dextran 60). Samples were weighed (for net fluid fluxes) and analyzed at bedside (for routine metabolites) and later in the laboratory (for total protein and interleukin-6). The in vitro recovery of glucose, glutamate, and glycerol were also investigated under different conditions.
  
  
  RESULTS
  Even brief perfusion with standard perfusion fluid resulted in a significant loss of volume from the microdialysis system. For albumin and Ringer-dextran 60 fluid, recovery was comparable to standard settings. Interleukin-6 (highest value close to 25,000 pg/ml) was sampled from all catheters, and total protein was analyzed from catheters perfused with Ringer-dextran 60 (average concentration, 234 mug protein/ml). There were detectable patterns of variations in the concentration of interleukin-6, seemingly related to concomitant variations in intracerebral conditions. In the present study, no direct comparison was made with the standard CMA 70 catheter (CMA Microdialysis, Stockholm, Sweden), but in vivo, the measured mean concentrations of glucose, glycerol, lactate, and pyruvate were comparable to those previously reported from standard catheters. In vitro, the recovery of metabolites was better when using Ringer-dextran 60 compared with albumin.
  
  
  CONCLUSIONS
  Microdialysis catheters with high-cutoff membranes can be used in routine clinical practice, allowing for sampling and analysis of cytokines and other macromolecules.
authors.affiliation: Department of Neurosurgery, University Hospital, Linköping, Sweden. Jan.Hillman@lio.se
authors.forename: Jan
authors.initials: J
authors.lastname: Hillman
authors.forename: Oscar
authors.initials: O
authors.lastname: Aneman
authors.forename: Chris
authors.initials: C
authors.lastname: Anderson
authors.forename: Florence
authors.initials: F
authors.lastname: Sjögren
authors.forename: Carina
authors.initials: C
authors.lastname: Säberg
authors.forename: Pekka
authors.initials: P
authors.lastname: Mellergård
mesh_terms: D001923:Brain Chemistry; D001930:Brain Injuries / Q000175:diagnosis / Q000378:metabolism*; D015600:Glasgow Coma Scale; D006801:Humans; D046911:Macromolecular Substances / Q000032:analysis*; D017551:Microdialysis / Q000379:methods*; D008970:Molecular Weight; D013997:Time Factors
chemical_list: D046911:Macromolecular Substances