Technology and Health Care 4 (1996) 67-76 IDS Press An intravascular microdialysis sampling system suitable for application in continuous biochemical monitoring of glucose and lactate K. Rabenstein 1 ,2, A.l. McShane 2 , M.1. McKenna 3 , E. Dempseyl,5, T.v. Keaveny4 and R. Freaneyl,3,* 1 Education and Research Centre 2 Department of Anaesthesia and Intensive Care 3 Metabolism Laboratory 4 Department of Vascular Surgery, St. Vincent's Hospital, Elm Park, Dublin 4, Ireland 5 Dublin City University, Glasnevin, Dublin 9, Ireland 67 Abstract. Direct sensor implantation for continuous biochemical monitoring has proved disappointing, but microdialysis sampling devices can serve as a biocompatible patient-sensor interface. We propose a novel "MiniShunt" extracorporeal microdialysis sampling circuit designed to sample core blood, and report the performance of different microdialysis probe membrane types and sizes with pumped and non-pumped blood flow in anaesthetised dogs. Discrete microdialysate and plasma samples collected during glucose and lactate monitoring were analysed with a YSI analyzer and showed microdialysis efficiency (% relative recovery) in excess of 95% for both analytes using fibres of greater than 70 mm 2 internal surface area. Pumped veno-venous extracorporeal blood microdialysis sampling of this type could provide a suitable interface for future multi-analyte on-line biosensor applications in critically ill patients. Keywords: Microdialysis, extracorporeal circulation, monitoring, physiologic, blood glucose, lactates 1. Introduction Repeated measurements of biochemical analyte concentrations in blood are a vital guide for thera- peutic decisions and management of critically ill patients. Intra-arterial probes for on-line continuous measurement of blood gas parameters and oxygen saturation are available [1]. However, monitoring of other biochemical analytes is currently still dependent on intermittent phlebotomy and discrete analysis. Continuous on-line monitoring of glucose, lactate, urea, creatinine, potassium and other metabolites should be possible using multi-sensor arrays and a suitable sampling system. While miniaturised -Dr. R. Freaney, Metabolism Laboratory, St. Vincent's Hospital, Elm Park, Dublin 4, Ireland. Tel.: +353 1 269 45 33, ext. 4513; Fax: +353 1 260 11 86. 0928-7329/96/$8.00 © 1996 - IDS Press. All rights reserved