Development and validation of a biparametric sensor for urea and creatinine in hemodialysis monitoring

The optimal dose of dialysis to be delivered is a subject of great interest because of its clinical and economic consequences. The classic Kt/V calcul ations have important erros, especially in high efficiency dialysis. The de velopment of a urea biosensor has made this monitoring easy. However urea i s not the only or the most important metabolite responsible for th symptoms of patients. There is a tendency to improve the dialysis tecnique, especia lly by using more biocompatible membranes with greater permeability and lar ger surface area. Consequently, in the future, monitoring of different moll ecular weight solutes can offer relevant information. In this article we de scribe the development and validation of a new biparametric sensor for urea and creatinine in hemodialysis monitoring. This device has been developed entirely at the department of Chemistry of t he Autonomous University of Barcelona. The analyser is based on a flow-inje ction analytical biosystem with two reactors. The enzymes used are creatini ne deiminase and urease, wich are covalently immobilized on controlled-pore glass beads and on a nylon open tubular reactor respectively. Once connect ed in the effluent dialysate, it automatically displays the cumulative urea and creatinine removal during the dialysis session. The analytical method was validated off-line by measuring urea and creatini ne from discrete effluent samples, after that the system was validated on-l ine during ten hemodialysis sessions by comparing it with the classical met hod of collecting all the effluent. The results agree with concurrent analyses using hospital laboratory method s. In the off-line experiments the correlation obtained was 0.99 for urea a nd 0.98 for creatinine. In the on-line studies, the correlation was 0.91 fo r urea and 0.97 for creatinine. We conclude that this biparametric sensor is accurate and reliable for the continuous monitoring of urea and creatinine removal during the dialysis se ssion.