Continuous monitoring of urea levels during hemodialysis

An ammonium ion-specific electrode system is evaluated for analysis of blood urea nitrogen from serum, plasma ultrafiltrate, or hemodialyzer dialysate fluid. The electrode shows a high sensitivity over clinically useful concentration ranges. Free serum ammonia, volatile amines, or urea ammonia after hydrolysis can be measured. In a double blind study excellent correlation was found for 187 blood urea nitrogen samples measured with the electrode with standard auto-analyzer techniques. Continuous monitoring of urea in dialysate fluid is described. Urea clearances were measured from dialysate effluent from an in vitro dialysis using conventional equipment. These values show excellent correlation to those from stnadard analysis methods. A continuous urea sensor for on-line hemodialysis application which can provide quantification of therapy is described.