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Related Experiment Videos

Clinical cerebral microdialysis: a methodological study.

P J Hutchinson1, M T O'Connell, P G Al-Rawi

  • 1Academic Department of Neurosurgery and Wolfson Brain Imaging Centre, University of Cambridge, United Kingdom. Peter.Hutchinson@dial.pipex.com

Journal of Neurosurgery
|July 7, 2000
PubMed
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Clinical microdialysis catheter length significantly impacts substance recovery in neurosurgical patients. Perfusion fluid and sample handling did not affect concentrations, but flow rate variations allowed for accurate recovery calculations.

Area of Science:

  • Neurosurgery
  • Neurochemistry
  • Biomedical Engineering

Background:

  • Clinical microdialysis is used to monitor cerebral extracellular chemistry in neurosurgical patients.
  • Variations in microdialysis application exist across institutions.
  • Key variables include catheter membrane length, perfusion fluid, flow rate, and analysis timing.

Purpose of the Study:

  • To assess the impact of varying microdialysis catheter characteristics on substance concentration.
  • To determine relative recovery and true extracellular concentration by adjusting flow rate and extrapolating to zero flow.
  • To compare substance concentrations from bedside enzyme analysis with off-line high-performance liquid chromatography (HPLC).

Main Methods:

  • Two adjacent microdialysis catheters were inserted into the frontal cortex of ventilated neurosurgical patients.

Related Experiment Videos

  • Catheter membrane length (10 mm or 30 mm), perfusion fluid (Ringer's or saline), and flow rate (0.1-1.5 microl/minute) were systematically varied.
  • Sample analysis was performed on-line and after storage; bedside enzyme analyzer results were compared with HPLC for glutamate.

    • Main Results:

    • Identical catheters yielded equivalent results; perfusion fluid and sample freezing/thawing did not alter concentrations.
    • Catheter membrane length significantly affected substance recovery.
    • Varying flow rates allowed for relative recovery calculation, showing approximately 70% recovery at 0.3 microl/minute and 30% at 1 microl/minute (10-mm membrane).
    • Glutamate concentrations from the enzyme analyzer correlated well with HPLC findings.

    Conclusions:

    • Catheter length is a critical factor in microdialysis substance recovery.
    • The extrapolation-to-zero-flow method, modified for flow rate variations, accurately calculates relative recovery.
    • Bedside enzyme analysis provides reliable glutamate measurements comparable to HPLC in this context.