Acute effects of dietary phosphorus intake on markers of mineral metabolism in hemodialysis patients: post hoc analysis of a randomized crossover trial.

BACKGROUND: Long-term dietary phosphorus excess influences disturbances in mineral metabolism, but it is unclear how rapidly the mineral metabolism responds to short-term dietary change in dialysis populations. METHODS: This was a post hoc analysis of a randomized crossover trial that evaluated the short-term effects of low-phosphorus diets on mineral parameters in hemodialysis patients. Within a 9-day period, we obtained a total of 4 repeated measurements for each participant regarding dietary intake parameters, including calorie, phosphorus, and calcium intake, and markers of mineral metabolism, including phosphate, calcium, intact parathyroid hormone (iPTH), intact fibroblast growth factor 23 (iFGF23), and C-terminal fibroblast growth factor 23 (cFGF23). The correlations between dietary phosphorus intake and serum mineral parameters were assessed by using mixed-effects models. RESULTS: Thirty-four patients were analyzed. In the fully adjusted model, we found that an increase in dietary phosphorus intake of 100 mg was associated with an increase in serum phosphate of 0.3 mg/dL (95% confidence intervals [CI], 0.2-0.4, p < .001), a decrease in serum calcium of 0.06 mg/dL (95% CI, -0.11 to -0.01, p = .01), an increase in iPTH of 5.4% (95% CI, 1.4-9.3, p = .01), and an increase in iFGF23 of 5.0% (95% CI, 2.0-8.0, p = .001). Dietary phosphorus intake was not related to cFGF23. CONCLUSIONS: Increased dietary phosphorus intake acutely increases serum phosphate, iPTH, and iFGF23 levels and decreases serum calcium levels, highlighting the important role of daily fluctuations of dietary habits in disturbed mineral homeostasis in hemodialysis patients.

Accuracy of a Nutrient Database in Estimating the Dietary Phosphorus-to-Protein Ratio and Using a Boiling Method in Low-Phosphate Hospital Diets.

The use of the dietary phosphorus-to-protein ratio (PPR) to reduce dietary phosphorus while maintaining protein intake is valuable for nutritional management in the dialysis population, but the actual PPR values in hospital meals have not been determined. We aimed to determine the accuracy of a nutrient database for estimating the PPR in low-phosphate hospital diets compared with the accuracy of chemical analysis and produce hospital diets with low-phosphate content by boiling meat for 30 minutes before cooking. The phosphorus and protein content of 26 cooked dishes selected from the hospital menu was estimated using a food composition table (FCT) and sent for chemical analysis. Comparisons of FCT-based estimated values with measured values for every 100 g of tested foods revealed an overestimation for the PPR both in plant-based dishes (mean difference ± SD, 4.1 ± 14.6 mg/g, P = 0.06), and in meats (2.1 ± 2.3 mg/g, P = 0.06). By boiling meats, we crafted diets with PPR as low as 8 mg/g. Caution should be exercised in estimating the PPR using a FCT in hospital diets and boiling should be used to prepare hospital meals. Such diets will be promoted for dialysis patients in both inpatient and outpatient settings.

Risk factors for severe hypocalcemia after parathyroidectomy in prevalent dialysis patients with secondary hyperparathyroidism.

PURPOSE: Hypocalcemia is one of the common complications after parathyroidectomy (PTX). Severe hypocalcemia (SH) can lead to tetany, cardiac arrhythmia and even sudden death. However, predictors for the development of SH in patients with secondary hyperparathyroidism demonstrated in some small-scale studies with a limited sample size remain inconclusive. METHODS: A retrospective chart review of 420 consecutive dialysis patients who underwent PTX during a 12-year period was performed. We checked serum levels of calcium (Ca), phosphorus (P), alkaline phosphatase (ALP) and intact parathyroid hormone (iPTH) for three consecutive days postoperatively. SH was defined as the minimum values of serum calcium lower than 1.875 mmol/L (7.5 mg/dL) within 3 days after operation. RESULTS: The mean (±SD) age of our study population was 53 ± 12 years, and more than half (57 %) were female. SH occurred in 37 % of the patients after PTX. Using a multivariate stepwise logistic regression analysis, lower preoperative levels of Ca (odds ratio 0.69, 95 % CI 0.60-0.79, P < 0.001), higher preoperative levels of iPTH (odds ratio 1.04, 95 % CI 1.00-1.07, P = 0.048), P (odds ratio 2.43, 95 % CI 1.49-3.95, P < 0.001) and ALP (odds ratio 1.08, 95 % CI 1.05-1.11, P < 0.001) were found to be independent predictors of occurrence of SH following PTX. CONCLUSIONS: The readily obtainable preoperative laboratory parameters including Ca, iPTH, P, and ALP will allow identification of a subgroup of patients who are at greater risk for the development of SH following PTX.