Potassium metabolism in continuous ambulatory peritoneal dialysis patients

Hypokalemia is common and may have contributed to the poor clinical outcome in peritoneal dialysis (PD) patients. In this study, we made a detailed investigation on the potassium metabolism in continuous ambulatory peritoneal dialysis (CAPD) patients and tried to find out the possible factors associated with the high prevalence of hypokalemia in PD patients.

A cross-sectional survey in 243 clinically stable CAPD patients was made in our PD center in 2010. Patients were divided into four groups according to whether they were anuric or not and different dialysis regimens. Patients' demographic data and data on potassium metabolism including dietary potassium intakes, residual renal potassium, and peritoneal dialysis potassium removal were collected.

The average potassium intake in our 243 PD patients was 32.1 ± 11.1 mmol/day. The total potassium removal was significantly higher in non-anuric patients as compared to anuric patients (33.2 ± 9.1 vs. 23.0 ± 4.7 mmol/day for 3 exchanges per day and 35.2 ± 8.9 vs. 28.6 ± 6.3 mmol/day for 4 exchanges per day, respectively, p < 0.01) and in anuric patients dialyzed with 4 exchanges per day as compared to anuric patients dialyzed with 3 exchanges per day (28.6 ± 6.3 vs. 23.0 ± 4.7 mmol/L, p < 0.05). Compared to non-anuric patients dialyzed with 3 exchanges per day, serum potassium level was significantly lower (4.1 ± 0.7 vs. 4.5 ± 0.7 mmol/L, p < 0.05) while the prevalence of hypokalemia was significantly higher (22.2% vs. 9.3%, p < 0.05) in non-anuric patients that dialyzed with 4 exchanges per day. There was a strong correlation between renal potassium removal and renal urea Kt/V (R(2) linear = 0.645, p < 0.05). In a linear multiregression analysis, dietary potassium intake, intracellular water (ICW) significantly positively predicted serum potassium level while dialysis exchanges, residual renal function (RRF), D/P potassium all significantly negatively predicted serum potassium levels.

Our study suggested that if potassium intake was limited in PD patients, we should be aware of the risk of hypokalemia with high doses of PD when patients have good RRF. Our study also suggested that potassium removal in PD patients may not necessarily reflect potassium intake even if serum potassium is normal, the effect of ICW should be considered when evaluating potassium homeostasis.