Mechanisms of Peritoneal Acid-Base Kinetics During Peritoneal Dialysis: A Mathematical Model Study.

Area of Science:

• Nephrology
• Biophysics
• Mathematical Modeling

Background:

• Acid-base balance is critical during peritoneal dialysis (PD).
• Previous models focused on lactate-driven bicarbonate generation.
• Understanding kinetic transport across the peritoneal membrane is essential.

Purpose of the Study:

• To develop a mathematical model for acid-base changes during PD.
• To elucidate the mechanisms of peritoneal bicarbonate and pH kinetics.
• To compare model predictions with experimental data.

Main Methods:

• Modified the Rippe 3-Pore model for solute and water transport.
• Incorporated an electroneutrality constraint on peritoneal fluid ions.
• Added a peritoneal CO2 mass-conservation constraint.
• Fitted the model to experimental pH and bicarbonate data.

Main Results:

• The model accurately predicted peritoneal bicarbonate concentration kinetics.
• Total peritoneal bicarbonate mass kinetics exceeded porous transmembrane transport.
• CO2 transport and conversion contribute to bicarbonate generation.
• Predicted pH kinetics closely matched experimental data.

Conclusions:

• Peritoneal dialysis acid-base kinetics involve electroneutrality, CO2 transport (porous and nonporous), and CO2 conversion to bicarbonate.
• These mechanisms are more complex than previously proposed lactate-centered models.
• The model provides a more comprehensive understanding of ion kinetics during PD.