Distribution volume assessment compartment modelling: theoretic phosphate kinetics in steady state hemodialys...

Hyperphosphatemia constitutes a major problem in end-stage renal disease patients. At this stage, dialysis efficacy usually plays an important role in obtaining phosphate levels within the normal range. Currently, no practical tool capable of making individualized predictions about phosphate changes during and after hemodialysis (HD) have gained clinical acceptance. As a result, optimal dialysis prescriptions seem to be difficult to achieve. The objective of the present study was to develop and test a quantitative tool to predict intradialytic and postdialytic (2 hours) phosphate kinetics in HD therapy. This included distribution volume assessment.

The approach included compartment modeling. Various model attempts were produced and tested using experimental data that included 2 treatment regimens; conventional and nocturnal HD, with 2-hour postdialysis rebound. Graphical comparison and determination of R(2) was applied to determine the best model variation.

1-, 2- and 3-compartment simulations were produced. Both 2- and 3-compartment model variations showed a close fit with the experimental data. However, a 3-compartment model showed the best graphical fit. This was supported by R(2) values in the 0.951-0.979 range.

The 3-compartment model seems promising for prediction about plasma phosphate and holds the potential to be employed as a decision support tool and to enhance optimal dialysis prescriptions. Furthermore, the results provide specific suggestions about the distribution of phosphate in the body. Despite the promising results, further data and testing are necessary to validate the initial results.