[Continuous measurement of cations in the blood-stream of patients (author's transl)].

An electrochemical flow-through system in the blood-stream of patients is described, which allows continuous measuring of Na+-, K+- and Ca++-concentrations. The ion-selective electrodes show excellent selectivity constants. Activity potentials of greater than 97% of the theoretical measurement characteristics of the electrodes (Nernst-factor) could be achieved. This electrochemical measuring device makes it possible to measure continuously the electrolyte activities in the blood. Results of direct patient measurements are demonstrated.