Sodium loss, extracellular volume overload and hypertension in peritoneal dialysis patients treated by automated peritoneal dialysis cyclers

Abstract

Introduction: Achieving sodium balance is important for peritoneal dialysis patients, as sodium excess may lead to hypertension and extracellular water expansion. We wished to determine whether greater sodium removal had adverse consequences. Methods: We calculated 24-h urinary and peritoneal sodium losses in peritoneal dialysis patients treated by automated cyclers, when attending for peritoneal membrane and bioimpedance assessments. Results: We reviewed 439 peritoneal dialysis patients, 56.7% male, average age 54.6 years, median sodium loss 110 (68–155) mmol/day. Sodium loss was strongly associated with urine volume, r = 0.37, protein nitrogen appearance rate, r = 0.29, and body cell mass, r = 0.21, all p < 0.001. We found no association with blood pressure or anti-hypertensive medication prescription, or extracellular water. On multivariable logistic regression analysis, sodium loss was associated with greater urine output, odds ratio 1.001, 95% confidence interval 1.00–1.001, p < 0.001, and protein nitrogen appearance (odds ratio 1.023, confidence interval 1.006–1.04), p = 0.008. Adjusting for body weight, sodium loss was associated with urine output (odds ratio 1.001, confidence interval 1.001–1.002, p < 0.001), and negatively with body fat index (odds ratio 0.96, confidence interval 0.93–0.99, p = 0.008) and co-morbidity grade (odds ratio 0.58, confidence interval 0.36–0.39, p = 0.023). Conclusion: Heavier peritoneal dialysis patients with greater estimated dietary protein intake (protein nitrogen appearance), those with greater residual renal function and peritoneal clearances, along with lower co-morbidity, had greater daily sodium losses. Adjusting for body weight, then sodium losses were greater with higher daily urine output, and lower in patients with proportionately more body fat and co-morbidity. Sodium losses would appear to primarily determined by body size and not associated with hypertension or extracellular water expansion.

Comparison of sodium removal in peritoneal dialysis patients treated by continuous ambulatory and automated peritoneal dialysis

“…Peritoneal sodium removal was also associated with the volume of icodextrin prescribed, supporting other studies which have shown that volume status is better maintained with icodextrin compare to 22.7 g/L glucose exchanges [26]. Whereas some smaller earlier studies did not demonstrate an effect of hypertonic glucose dialysates and peritoneal sodium losses [9], we noted a univariate association, which would be expected as hypertonic dialysates would be expected to increase ultrafiltration [10, 24]. There was a weak association between higher mean arterial blood pressure and lower peritoneal sodium losses, and previous studies have either reported a similar association or no effect of peritoneal sodium losses on blood pressure [9, 27].…”

“…These patients had greater residual renal function and urinary sodium losses, thus over-all losses were similar between modalities, supporting the results of smaller studies [10, 24]. As with many centres we practice incremental dialysis, with peritoneal dialysis prescriptions taking into account residual renal function [25], and as such patients with greater residual renal function and urinary sodium losses had correspondingly lower peritoneal sodium losses.…”

Peritoneal sodium removal compared to glucose absorption in peritoneal dialysis patients treated by continuous ambulatory peritoneal dialysis and automated peritoneal dialysis with and without a daytime exchange

“…[24,25] Earlier studies reported that PD technique failure was more common for fast transporters, but this risk was reduced or reversed with the introduction of APD cyclers in combination with the liberal use of icodextrin. [26,27] We noted lower peritoneal sodium removal to glucose absorption when patients did not use icodextrin, irrespective of whether they used CAPD or APD and CCPD. On multivariable analysis treatment with APD remained a significant factor associated with lower peritoneal sodium removal and higher glucose absorption, but this is most likely due to not using icodextrin.…”