Clinical microdialysis in the neurosurgical intensive care unit: promises and pttfalls

Introduction: Microdialysis permits the analysis of substances in the extracellular space of the brain Ammo acids, energy metabolites and cations are commonly measured, and alterations of these compounds correlate with pathophystotogical events and outcome Here we report our experience with the capabilities, limitations and safety of this technique. Materials and Methods: We performed microdialysis monitoring in 88 patients for a total of 5213 hours of monitoring Loop microdialysis probes with were placed in the right frontal cortex during ICP pressure transducer insertion or in cerebral cortex exposed duhng decompressive craniotomy The probes were perfused at 2 ul/min with normal saline and 60 ul samples were collected every 30 minutes. Arnino acids and cations were measured by HPLC, and glucose and lactate were measured using an enzyme electrode analyzer (Yellow Springs Instruments) Results: Microdialysis monitoring is labor intensive and requires dose attention to probe and fluidic line integrity during patient transport and manipulation. We had no infectious complications, and had a single instance of a small intraparenchymal hematoma near the microdialysis probe and an adjacent substantially larger pressure transducer. OfMine analysis leads to time delays between sample acquisition and results, but implementation of glucose and lactate analysa in the NICU dramatically improved sample throughput and raised the potential of clinical relevance. Elevations of excitatory amino acids, lactate and potassium, and reductions in extracellular glucose correlated with pathophysiotogical events and poor outcome Conclusions: Microdialysis is a safe and valuable research tool in neurointensh/e care Aoohcafan to clinical decision makina raauires develooment of robust on-line or near on-line analysis.