Modeled Daily Ingested, Absorbed and Bound Phosphorus: New Measures of Mineral Balance in Hemodialysis Patients

Abstract

Background: Control of predialysis serum phosphorus in hemodialysis patients is challenging. We explored the utility of a novel kinetic phosphorus modeling program. Methods: As part of a quality assurance program, urea kinetic modeling results were combined with those from phosphorus kinetic modeling to compute modeled daily ingested phosphorus (DIP) and components making up this metric, including absorbed, bound, and nonabsorbed, nonbound phosphorus. Results: In 182 hemodialysis patients, DIP averaged 1,089 ± 348 mg/day in men and 934 ± 292 in women (p < 0.002) and correlated substantially with body weight. DIP/kg bodyweight (12.8 ± 3.40 mg/kg) was not significantly different between the sexes. Prescribed equivalent binder dose (EBD) was 4.98 ± 3.61 and 4.53 ± 3.02 g/day in men and women, respectively (p NS). Protein catabolic rate (PCR) was significantly higher in men (64.4 ± 18) g/day vs. women (48.2 ± 15.6, p < 0.001), and the DIP/PCR ratio was 17.4 ± 4.81 in men vs. 20.1 ± 5.76 in women (p < 0.001). Presence of residual kidney function was associated with a lower prescribed EBD dose (4.08 ± 2.62 vs. 5.38 ± 3.81 g/day, p < 0.01). Self-reported poor binder compliance was associated with higher DIP or DIP/kg as well as higher prescribed EBD. In anuric patients, DIP/kg was increased in patients consuming diets with high phosphate additive content and those reporting poor compliance with the prescribed dose of phosphate binders. Conclusions: The combination of urea kinetic and phosphorus modeling can be used to estimate measures related to phosphorus intake. High DIP/PCR or DIP/kg body weight values in anuric patients suggest consumption of a diet high in phosphorus additives or noncompliance with the prescribed amount of phosphorus binders.

Phosphate kinetic modeling as an estimate of daily ingested phosphate in hemodialysis patients with or without residual kidney function

“…In another report by Viaene et al (2012), there is a correlation between RKF and serum P level [16]. Also, RKF was associated with a lower prescribed binder dose in another study [17]. Coping with these results, the present study showed higher pre-dialysis P mean levels in the anuric group than in RKF patients.…”

“…The different outputs of this Daugirdas model were used in the context of quality assurance activities by other researchers to be tested for importance and validity. One of them is the study of Kapoian et al (2019) that aimed to determine if the new DIP or DABP metrics might be of great utility in analyzing the etiologies of high pre-dialysis serum P in HD cases [17]. Our study used the same model outputs with a different aim to test its validation to predict DIP in patients with and without RKF, which applied in the presence of simple clinical and laboratory data as the total weekly binder dose and pre-dialysis serum P, we reported higher estimated P which removed on HD and lowered P binder dosage that was needed in RKF than in anuric patients, this is in concordant with Kapoian study [17].…”

The dietary supplement chitosan lowers serum phosphorus in a hemodialysis patient not tolerating prescription medications

“…This leads to an estimate of a phosphorus binding capacity of 41 mg/g of chitosan (146 mg/3.5 g chitosan), similar to calcium carbonate 10 . Kapoian et al have devised a simpler method to estimate daily dietary phosphorus intake: multiplying body weight with 12.8 ± 3.4 mg per kg 11 . Remarkably, this method leads to the same result, 1200 mg/day, as the above calculations.…”

Comparison of modeled versus reported phosphate removal and modeled versus postdialysis serum phosphate levels in conventional hemodialysis

“…The phosphate kinetic model has been described previously. 3,5 See Appendix A for details. We made slight modifications to the model, lowering the coefficient for plasma water flow rate to account for a slightly higher intradialytic average hematocrit level than that assumed (33%) in the original model.…”

“…The average predicted phosphate removal with this model in the HEMO study patients was 1023 mg/treatment, but phosphate removal was never measured in that trial. We also extended the intradialytic part of the model to the interdialytic period, and developed a metric designed to simplify and quantitate the role of prescribed phosphate binders 4,5 . The ultimate goal of the model is to be able to predict the effect of changes in extracorporeal therapy and/or binder dose on the predialysis serum phosphate levels.…”