Solute-solver: a web-based tool for modeling urea kinetics for a broad range of hemodialysis schedules in multiple patients.

Practical application of urea kinetic modeling to measure the delivered dose of hemodialysis is hampered by lack of a reference or gold-standard program that would be widely available and freely distributed. We developed and here describe an open-source JavaScript tool, "Solute-Solver," capable of batch processing of urea kinetics calculations. The Solute-Solver online interface is available at (www.ureakinetics.org); in addition, the tool can be used as a standalone HTML file that is designed to be run using a web browser. Solute-Solver is written in uncompiled JavaScript for transparency and easy modification, and the source code is available for download and modification. The program uses fourth-order Runge-Kutta numerical integration applied to a variable-extracellular-volume 2-pool model to compute a variety of clearance measures, including 1-pool and 2-pool Kt/V, "standard" weekly Kt/V, and other equivalent clearance measures. The program accepts comma- or semicolon-delimited input (which can be produced from a spreadsheet) and generates a separator-delimited output file that can be imported back into a spreadsheet or other database. The program also produces individual patient-by-patient report pages. It typically provides kinetic output for 300 patient treatments in 30-60 seconds. Advantages of this program over previously available equations and algorithms include the capacity to properly model such newer dialysis schedules as 6-times-weekly short daily or nocturnal hemodialysis, as well as account for substantial variation in residual renal function. Ultimately, this effort may promote wider use of formal urea modeling and facilitate research that requires measurement of hemodialysis or hemodialysis adequacy, especially involving the newer expressions of continuous equivalent clearance, and expressions of clearance normalized to body surface area.