Institute of Nephrology, First Hospital, Peking University, Beijing, P.R. China.
Background: Hyperphosphatemia is common in dialysis patients and is influenced significantly by dietary protein intake. In this study, we investigated phosphorous control and the metabolic balance of phosphorus and calcium in our peritoneal dialysis patients.
Methods: Forty-one clinically stable continuous ambulatory peritoneal dialysis patients using peritoneal dialysis solution with a calcium concentration of 1.75 mmol/L participated in the study. Calcium carbonate was used as the phosphate binder. Dietary calcium, phosphorus, and protein intake were calculated for each patient from a 3-day dietary record; 24-hour urine, dialysate, and fasting blood were collected, and calcium, phosphorus, and protein levels in serum, urine, and dialysate were measured.
Results: Dietary protein, phosphorus, and calcium intake were 0.79 ± 0.27 g/kg/day, 595.9 ± 174.8 mg/day, and 441.9 ± 212.7 mg/day, respectively. Peritoneal dialysis removed 241.9 ± 87.2 mg/day phosphorus, whereas 45.4 ± 65.8 mg phosphorus was removed via urine. Hyperphosphatemia (> 1.8 mmol/L) occurred in 53.7% of patients despite the fact that 61% of hyperphosphatemic patients received calcium carbonate. A mean of 52.6 ± 83.5 mg/day calcium was absorbed from the dialysis solution. Eight patients (19.5%) presented with hypercalcemia. Serum phosphorus level correlated significantly with dietary protein intake (r = 0.508, p < 0.01). However, the serum calcium level did not correlate with calcium intake from diet or dialysate.
Conclusions: The incidence of hyperphosphatemia is still relatively high despite the low protein and low phosphorus intake in our peritoneal dialysis patients. A positive calcium balance was common in our patients using dialysis solution containing 1.75 mmol/L calcium, which needs to be further studied.
Key words: hyperphosphatemia, calcium and phosphate balance, diet, peritoneal dialysis
方法：參與者為 41 位臨床狀況穩定的連續攜帶式腹膜透析（CAPD）接受者，透析液之鈣濃度為 1.75 mmol/L。研究期間，磷酸鹽的結合劑為碳酸鈣。調查人員對病人在 3 天內磷、鈣、及蛋白質的攝取量作出記錄，並測量病人血清、尿液、及透析液中磷、鈣、及蛋白質的濃度。 結果：病人每天的蛋白質、磷、及鈣的攝取量分別為 0.79 ± 0.27 g/kg、595.9 ± 174.8 mg、及 441.9 ± 212.7 mg；每天經透析清除的磷為 241.9 ± 87.2 mg，經尿液排出的磷則為 45.4 ± 65.8 mg。高磷酸鹽血症（> 1.8 mmol/L）的發生率為 53.7%，而在這些病人之中，曾接受碳酸鈣的有 61%。每天從透析液吸收的鈣平均為 52.6 ± 83.5 mg，出現高鈣血症者則有 8 人（19.5%）。血清磷濃度與飲食中蛋白質的攝取量呈顯著的正相關（r = 0.508，p < 0.01）；然而血清鈣濃度與飲食或透析液中鈣的攝取量之間，卻缺乏顯著相關性。
結論：本研究的腹膜透析接受者維持偏低的蛋白質及磷攝取量，然而高磷酸鹽血症的發生率仍然相對偏高。在採用鈣濃度為 1.75 mmol/L 的透析液下，鈣的正平衡頗為常見；但這仍有待更進一步的調查。
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