Improving the recovery of S100B protein in cerebral microdialysis: Implications for multimodal monitoring in neurocritical care

Introduction: Cerebral microdialysis is an established research too] 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 100 mL 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 (TM) 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. Conclusion: 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. (C) 2009 Published by Elsevier B.V.