Claims
- 1. The method of determining the level of a predetermined metabolically important species in serum, without withdrawing blood or entering a sensor into the bloodstream, comprising the steps of:
- diverting at least a portion of a dialysate effluent stream, obtained from equilibration with blood through a hemodialyzer, through a sampling apparatus, including an ion-specific electrode sensitive to a desired species;
- producing an electrode EMF proportional to the concentration of the sensed species; and
- converting the EMF to data indicating the dialysate concentrations of the species and determining the serum levels of the species from such data.
- 2. The method as in claim 1, wherein:
- serum urea is monitored by diverting the dialysate effluent through an immobilized ureas column, wherein the urea is hydrolized to ammonia, and the concentration of ammonium-ion is sensed by the electrode.
- 3. The method as in claim 2, wherein:
- an equal volume of buffer solution is added to the dialysate effluent prior to sampling, thereof.
- 4. The method as in claim 1, wherein:
- serum phosphate is monitored by maintaining a partial pressure of oxygen in a reservoir of the dialysate effluent and a phosphate ion sensitive electrode is used to analyze the dialysate effluent.
- 5. The method as in claim 4, wherein:
- buffer is added to the dialysate effluent in the ratio of fifty parts buffer to one part dialysate effluent.
- 6. An apparatus for monitoring a blood serum metabolite by analyzing dialysate effluent equilibrated with blood via a hemodialyzer, comprising:
- diverting means for diverting at least a portion of the dialysate effluent into a sampling apparatus;
- sampling means in the sampling apparatus for selectively sampling a predetermined metabolite species present in the dialysate effluent, said sampling means including an ion-specific electrode for producing an EMF proportionate to the concentration of the species in the dialysate effluent; and
- means for converting the EMF to dialysate concentrations, which are, in turn, used to determine serum concentration of the species.
- 7. An apparatus as in claim 6, wherein:
- the sampling apparatus continuously samples the species in the dialysate effluent; and
- a recording device is connected to the means for converting the electrode EMF to record the species concentrations during hemodialysis.
- 8. An apparatus as in claim 6, further comprising:
- means to add a buffer solution to the dialysate effluent prior to sampling thereof, said means including a source of buffer solution; and means to pump an aliquot of said dialysate effluent and a selected quantity of buffer to said sampling means.
- 9. An apparatus as in claim 6, wherein:
- a plurality of calibrated solutions are connected to be added to the dialysate effluent prior to sampling thereof, to detect any drifts in the electronics, or other aberrations, and to provide a check on the stability and respone of the electrode with time.
- 10. An apparatus as in claim 6, wherein:
- the predetermined metabolite species is urea; the sampling apparatus includes an immobolized ureas column, through which the dialysate effluent is passed, during which the urea in the dialysate effluent is hydrolized to ammonia; and
- the electrode is a selective ammonium-ion sensitive electrode.
- 11. An apparatus for determining the level of a predetermined metabolically important species in serum, without withdrawing blood or entering a sensor into the bloodstream, comprising:
- diverting means for diverting at least a portion of a dialysate effluent stream, obtained from equilibration with blood through a hemodialyzer, through a sampling apparatus, including an ion-specific electrode sensitive to a desired species;
- means to produce an electrode EMF proportional to the concentration of the sensed species; and
- means to convert the EMF to data indicating the dialysate concentrations of the species and to determine the serum levels of the species from such data.
- 12. Apparatus as in claim 8, wherein said means to pump comprises a peristaltic pump, said means to add a buffer solution to the dialysate effluent comprising a line which joins with said diverting means downstream of said peristaltic pump;
- said sampling means including an immobilized ureas column through which dialysate effluent is adapted to be passed for hydrolysis of urea to ammonia; and
- said ion-specific electrode is an ammonium-ion sensitive electrode with an internal reference probe.
Government Interests
The invention described herein was made in the course of work under a grant or award from the Department of Health, Education and Welfare.
US Referenced Citations (9)