Peritoneal Dialysis Solutions

Sodium

Sodium overload complicated by fluid overload and hypertension commonly occurs in patients with kidney failure, including those receiving PD, particularly those with fast peritoneal solute transfer rates or low levels of residual kidney function. Removal of sodium in PD is achieved primarily by convection through ultrafiltration. Generally, the sodium concentration in PD solutions is 131–134 mmol/L. With a standard sodium PD solution prescribed for 8L/day, approximately 1.68 g (73.08 mmol) of sodium can be expected to be removed from the body. Other factors reported to promote sodium removal include achieving higher ultrafiltration volume (e.g., by higher prescribed exchange volumes, higher PD solution glucose concentrations) and shorter dwell time (particularly in fast peritoneal solute transfer rates).

An alternative strategy for augmenting peritoneal sodium removal is the use of low-sodium PD solutions (125 mmol/L). In a multicenter randomized controlled trial of low-sodium PD solution (125 mmol/L) versus standard-sodium PD solution (134 mmol/L) in 82 hypertensive PD patients from 17 sites, the low-sodium PD regimen resulted in higher mean daily sodium removal (0.39 g) compared to the standard-sodium solution at 12 weeks and a decrease in both systolic and diastolic blood pressure by 11 and 5 mm Hg, respectively, thereby allowing reduction in antihypertensive medication usage. The standard-sodium solution resulted in lower daily sodium removal (0.07 g), minor decrease of systolic blood pressure (1 mmHg), and no change in diastolic blood pressure at 12 weeks. These promising results are, however, based on relatively small size trials, such that the applicability and effectiveness of low-sodium PD solutions in broader clinical settings have not yet been demonstrated.

Potassium

Patients with CKD often suffer from hyperkalemia due to a decrease in kidney clearance. PD solutions typically do not contain any potassium in order to maximize the concentration gradient across the peritoneal membrane, thereby promoting potassium diffusion into the peritoneal fluid. On average, daily peritoneal potassium removal in PD patients is estimated to be of the order of 30.4 mmol/day and is directly proportional to the dwell time of each exchange. Potassium removal is also dependent on residual kidney function, intracellular volume, and dietary intake in patients receiving PD. Intracellular volume and dietary intake were shown to have a positive correlation with serum potassium level, while residual kidney function and dialysis exchanges had a negative correlation with serum potassium level.

Calcium

There are three levels of calcium available in commercially manufactured dextrose-based PD solutions: 1 mmol/L, 1.25 mmol/L, and 1.75 mmol/L ( Table 22.1 ). Most commonly, PD solutions with 1.25 mmol/L calcium are used for treatment unless there are clinical indications to use high-calcium (1.75 mmol/L) PD solutions (e.g., hypocalcemia, such as may occur following parathyroidectomy) or low-calcium (1.00 mmol/L) solutions (e.g., hypercalcemia). A glucose polymer PD solution, icodextrin, is currently only available with a 1.75 mmol/L calcium concentration.