Peritoneal Dialysis I: Introduction and Procedure

Peritoneal dialysis uses the peritoneum as a natural filter through diffusion, osmosis, and ultrafiltration. Waste products and electrolytes move from high concentrations in the blood to low concentrations in the dialysate across the peritoneal membrane. Water is drawn into the hyperosmotic dialysate by osmotic pressure, removing excess fluid while solutes are carried along through convection.

Dacron cuffs secure the catheter in place and act as a barrier to prevent microorganisms from entering the peritoneum. Over time, fibrous tissue grows around these cuffs, anchoring the catheter more firmly and providing long-term stability. This design helps reduce infection risk and maintains catheter function.

The three phases are inflow, dwell, and drain. During inflow, typically 2 liters of dialysis solution is infused over about 10 minutes. The dwell phase lasts 4-6 hours, allowing the solution to absorb waste. Finally, the drain phase removes the fluid over 20-30 minutes, completing one exchange cycle.

Dextrose is the most common osmotic agent because it is safe and cost-effective. It creates an osmotic gradient that draws water across the peritoneal membrane into the peritoneal cavity, enhancing ultrafiltration and fluid removal. However, high glucose absorption can lead to complications like hyperglycemia and peritoneal membrane dysfunction over time.

Solution volume and composition depend on individual patient needs and peritoneal cavity size. An average-sized person typically uses 2 liters, while larger individuals may require 3 liters. Smaller volumes are used for patients with smaller bodies, pulmonary compromise, or inguinal hernias. Dialysate composition, including glucose and electrolyte concentrations, is adjusted to balance fluid and electrolyte levels.

Icodextrin and amino acid solutions are alternatives to dextrose. Icodextrin is an iso-osmolar preparation that induces ultrafiltration through its oncotic effect, reducing glucose absorption complications. Amino acid PD solutions provide nutritional support for patients requiring supplementation, offering flexibility in managing individual patient needs.

Membrane permeability varies among patients and affects the peritoneal membrane's ability to transfer solutes and water, influencing PD efficiency. Dwell time—the length the dialysate remains in the peritoneal cavity—impacts both waste and fluid removal. Together, these factors determine how effectively peritoneal dialysis systems and complications can be managed during treatment.