Assessment of dialysis adequacy using the dialysate urea monitor: preliminary experience of the dialysate urea monitor

Stability of Urea and Creatinine in Spent Hemodialysate

Urea and creatinine levels in spent hemodialysates showed only small declines in spite of incubation at 37° C for 36 hours. In the determination of dialysate-side solute removal, it would seem prudent to keep spent dialysate cold during collection to retard bacterial breakdown of these waste products.

Developments in online monitoring of haemodialysis patients: towards global assessment of dialysis adequacy

PURPOSE OF REVIEW

Online monitoring of haemodialysis provides more detailed and more immediate measurement of parameters currently assessed during haemodialysis. It can also assess novel variables that are not routinely measured and could intensively monitor the haemodynamic response to dialysis. In an era of expanding numbers of increasingly dependent patients on dialysis, the ability to provide intensive and extensive monitoring of haemodialysis is a boon. The technology available to do this is rapidly becoming more sophisticated, more widely available and more diverse than ever before.

RECENT FINDINGS

Adequacy of urea removal is of crucial importance to mortality on haemodialysis, and online monitoring of urea removal is now achievable using a number of different methods. Some of these methods also measure sodium flux, allowing precise monitoring of sodium balance. Haemodynamic disturbance can be assessed using relative blood volume monitoring equipment, or more directly with non-invasive pulse-wave analysis giving a continuous blood pressure reading. The attributes of each of the separate technologies involved are examined.

SUMMARY

Online monitoring of a variety of pertinent parameters during haemodialysis provides an array of tools that are steadily being incorporated into routine clinical practice. Research is also benefiting from novel insights into the process of haemodialysis provided by this technology.

Estimation of delivered dialysis dose by on-line monitoring of the ultraviolet absorbance in the spent dialysate

BACKGROUND

Several methods are available to determine Kt/V, from predialysis and postdialysis blood samples to using on-line dialysate urea monitors or to ionic dialysance using a conductivity method. The aim of this study is to compare Kt/V calculated from the slope of the logarithmic on-line ultraviolet (UV) absorbance measurements, blood urea Kt/V, dialysate urea Kt/V, and Kt/V from the Urea Monitor 1000 (UM; Baxter Healthcare Corp, Deerfield, IL).

METHODS

Thirteen uremic patients on chronic thrice-weekly hemodialysis therapy were included in the study. The method uses absorption of UV radiation by means of a spectrophotometric set-up. Measurements were performed on-line with the spectrophotometer connected to the fluid outlet of the dialysis machine; all spent dialysate passed through a specially designed cuvette for optical single-wavelength measurements. UV absorbance measurements were compared with those calculated using blood urea and dialysate urea, and, in a subset of treatments, the UM.

RESULTS

Equilibrated Kt/V (eKt/V) obtained with UV absorbance (eKt/Va) was 1.19 +/- 0.23; blood urea (eKt/Vb), 1.30 +/- 0.20, and dialysate urea (eKt/Vd), 1.26 +/- 0.21, and Kt/V in a subset measured by the UM (UM Kt/V) was 1.24 +/- 0.18. The difference between eKt/Vb and eKt/Va was 0.10 +/- 0.11, showing a variation similar to the difference between eKt/Vb and eKt/Vd (0.03 +/- 0.10) and in a subset between eKt/Vb and UM Kt/V (-0.02 +/- 0.11).

CONCLUSION

The study suggests that urea Kt/V can be estimated by on-line measurement of UV absorption in the spent dialysate.