Bedside clinical chemistry: from catheter tip sensor chips towards micro total analysis systems

With the start of the development of tiny chip chemical sensors in the seventies and eighties, which can easily be mounted in the tip of a catheter, it was thought that clinical chemistry would enter the operating theatre, the intensive care unit, etc. Continuous in vivo monitoring of many important blood variables should replace the sample technique with off-line laboratory determinations. However, problems with sensor stability and biocompatibility prevented this development. At the present moment a new field of research is unfolding rapidly: the micro Total Analysis Systems (μTAS). The result is that very small equipment for (bio)chemical analysis becomes available, operating completely automatic, because it contains all necessary components in one liquid handling board, like sample inlet facilities, micropumps, micromixers/reactors, sensors and the control electronics. These micro systems can operate without the necessity of being handled by trained laboratory personnel and are thus suitable for bedside monitoring. The state of the art in the field of μTAS will be discussed in this paper, with emphasis on suitability for continuous monitoring.