Abstract
The disruptive action of an acute or critical illness is frequently manifest through rapid biochemical changes that may require continuous monitoring. Within these changes, resides trend information of predictive value, including responsiveness to therapy. In contrast to physical variables, biochemical parameters monitored on a continuous basis are a largely untapped resource because of the lack of clinically usable monitoring systems. This is despite the huge testing repertoire opening up in recent years in relation to discrete biochemical measurements. Electrochemical sensors offer one of the few routes to obtaining continuous readout and, moreover, as implantable devices information referable to specific tissue locations. This review focuses on new biological insights that have been secured through in vivo electrochemical sensors. In addition, the challenges of operating in a reactive, biological, sample matrix are highlighted. Specific attention is given to the choreographed host rejection response, as evidenced in blood and tissue, and how this limits both sensor life time and reliability of operation. Examples will be based around ion, O2, glucose, and lactate sensors, because of the fundamental importance of this group to acute health care.
Highlights
Physiological processes operate under highly dynamic conditions that are controlled by a multitude of biofeedback systems operating on both long and short term timescales
The plasticisers assessed in this study showed varying degrees of toxicity, and reinforce the desirability of pre-use screening
Measurement uncertainty is further compounded by the catheter wall effect, where catheter tip impaction against a vessel wall advantage over an electrochemical sensor in that a sustained flux of O2 is not needed for response and so external transport constraints in vivo are reduced
Summary
Physiological processes operate under highly dynamic conditions that are controlled by a multitude of biofeedback systems operating on both long and short term timescales. These changes take place on highly compressed time scales and justify frequent, if not continuous, measurement, for both a better fundamental understanding and the better management of disease These variables can be considered to be highly labile and their dysregulation representsmajor failure of homeostatic control. The cell, tissue, and whole organism hierarchy gives us a dimensional scale across which we can select monitoring options at the supra-cellular level For clinical purposes, it is at the whole organism end of the range that we can see direct clinical value. There is a deviation from normal set points for a biochemical parameter, but moment to moment fluctuations that might change in dynamic character and could contain added information This has gone unrecognised because continuous tracking is not available, and the minor fluctuations nominally trivial.
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