A system for the measurement of a metabolite in a physiological fluid is disclosed which comprises a catheter which includes an internal metabolite sensor downstream from a semipermeable region where dynamic equilibrium is attained between the external metabolite and a higher concentration of the same...http://www.google.de/patents/US4705503?utm_source=gb-gplus-sharePatent US4705503 - Metabolite sensor including a chemical concentration sensitive flow controller for a drug delivery system
