Hypercalcaemia, hypermagnesaemia, hyperphosphataemia and hyperaluminaemia in CAPD: improvement in serum biochemistry by reduction in dialysate calcium and magnesium concentrations.

Phosphate binders are necessary to control hyperphosphataemia in the majority of dialysis patients. Whilst aluminium salts are efficient phosphate binders, their use is associated with toxic side effects. Calcium salts are a widely used alternative, but hypercalcaemia is a common side effect, limiting their use and raising concern about metastatic calcification. Reduction of the dialysis fluid calcium concentration has been shown to reduce hypercalcaemia in haemodialysis patients, with an associated decrease in serum PTH. We analysed the effect of reduced calcium/magnesium (1.25/0.25 mmol/l), 40 mmol/l lactate, PD fluid (PD4) on 11 CAPD patients with uncontrollable hypercalcaemia (> 2.65 mmol/l) and hyperphosphataemia (> 1.80 mmol/l). Only 1 patient remained hypercalcaemic, while phosphate fell in 6 patients (2.23 +/- 0.16 on no binder, to 1.68 +/- 0.08 mmol/l at 6 months (p < 0.05), but was unchanged in 5 (2.10 +/- 0.15 to 2.48 +/- 0.14 mmol/l [p = NS]). Overall mean calcium x phosphate product changed little. However, in a subgroup it fell significantly (p < 0.05). Geometric mean iPTH rose, but not significantly. The subgroup of patients whose calcium x phosphate product fell, exhibited a much smaller rise in iPTH than the others (57.3-73.2 vs. 52.8-167.1 pg/ml). 1.25-Dihydroxyvitamin D3 was subnormal in all patients. Mean serum magnesium fell from 1.24 +/- 0.06 to 0.89 +/- 0.04 mmol/l (p < 0.001), whilst mean serum bicarbonate rose significantly (25.2 +/- 0.4 to 28.9 +/- 1.2 mmol/l; p < 0.01). Withdrawal of aluminium-containing phosphate binders resulted in mean serum aluminium falling significantly from 31.1 +/- 5.7 at start of PD4 to 15.4 +/- 2.7 mu g/l at 6 months (p < 0.05). In summary, in around 50% of CAPD patients with persistent hypercalcaemia and hyperphosphataemia, reduction in PD fluid calcium can produce significant improvement in phosphate, reduction of calcium x phosphate product, and enable avoidance of aluminium-containing phosphate binders. Patients whose calcium and phosphate control remains poor, still benefit from the reduction, or cessation, of oral aluminium intake.

Correlation of bone histology with parathyroid hormone, vitamin D3, and radiology in end-stage renal disease.

We analyzed transiliac bone biopsy specimens from 30 end-stage renal failure patients, taken at the time of admission for CAPD training. Results were compared with values of iPTH, bone alkaline phosphatase, 1,25-dihydroxyvitamin D3, skeletal survey, quantitative computed tomography (QCT) and single photon absorptiometry (SPA) bone density measurements. Osteitis fibrosa was the most common histological diagnosis, present in 15 of the 30 patients (50%), with eight classified as "severe" and seven as "mild." Eight patients (27%) had adynamic bone lesion, four mixed renal osteodystrophy (13%), and two (7%) osteomalacia. The mean age of the adynamic group was higher than the osteitis fibrosa group (41 +/- 12.1 vs. 56 +/- 10.2 years; P < 0.01), and than the mixed group (39 +/- 7.5 vs. 56 +/- 10.2 years; P < 0.02). Levels of iPTH enabled discrimination between groups, but not between individual patients, and values correlated with bone alkaline phosphatase (r = 0.62; P < 0.001). Erosion of the terminal phalanges was seen on the plain X-rays of 7 of 15 patients with mild or severe OF, and in three patients with another diagnosis. The majority of patients (> 90%) had bone density measurements within the normal range. No significant correlation existed between QCT or SPA scores and any of the histomorphometric parameters, or iPTH. We conclude that iPTH is the most helpful non-invasive investigation in this group of patients. Plain X-ray of the hands is the most useful radiological investigation, but single measurements of bone density are not diagnostic.

Effect of radiotherapy on peritoneal function in continuous ambulatory peritoneal dialysis.

A 25-year-old male patient underwent abdominal radiotherapy following the discovery of lymphadenopathy associated with a testicular teratoma. Prior to treatment, his peritoneal mass transfer area coefficients were within normal limits. One and 2 months after treatment, peritoneal permeability had increased to the extent that continuous ambulatory peritoneal dialysis was rendered impractical.

Calcium and magnesium mass transfer in peritoneal dialysis patients using 1.25 mmol/L calcium, 0.25 mmol/L magnesium dialysis fluid.

OBJECTIVE: To examine the effect of a reduced calcium/magnesium dialysis fluid (1.25/0.25 mmol/L, respectively) on calcium and magnesium mass transfer in both 1.36% and 3.86% glucose solutions. DESIGN: Each patient underwent four test exchanges, two with a standard dialysis fluid containing 1.36% and 3.86% glucose, and two with a reduced calcium/magnesium fluid containing 1.36% and 3.86% glucose. Calcium and magnesium were measured in dialysate and serum at 0 and 240 minutes. SETTING: Single renal unit of a university teaching hospital. PATIENTS: Sixteen patients established on CAPD, and peritonitis-free, for at least 3 months. RESULTS: A lower dialysate calcium results in negative mass transfer when serum-ionized calcium exceeds dialysate calcium (mean -0.21 +/- 0.15 mmol/exchange), and positive mass transfer when serum-ionized calcium is less than dialysate calcium in 1.36% glucose solutions (mean 0.57 +/- 0.18 mmol/exchange). A negative correlation was found between serum-ionized calcium level and calcium mass transfer. With a 3.86% reduced calcium/magnesium solution, calcium mass transfer is always negative (-0.88 +/- 0.18 mmol/exchange) due to ultrafiltration and solute drag. Fifteen patients were found to be hypermagnesemic at the time of the study. Magnesium mass transfer was neutral with the standard 1.36% glucose fluid (mean -0.01 mmol/exchange), but negative with the reduced calcium/magnesium 1.36% glucose fluid (mean -0.58 +/- 0.13 mmol/exchange). With the 3.86% glucose solution, both fluids produced negative magnesium mass transfer (mean -0.32 +/- 0.11 and -1.07 +/- 0.11 mmol/exchange for standard and reduced calcium/magnesium fluids, respectively). CONCLUSIONS: We conclude that this fluid formulation should reduce hypercalcemia and hypermagnesemia in CAPD patients.

Low-calcium dialysis fluid and oral calcium carbonate in CAPD. A method of controlling hyperphosphataemia whilst minimizing aluminium exposure and hypercalcaemia.

Oral calcium carbonate is an effective phosphate binder in dialysis patients. Its use minimizes aluminium intake, and by maintaining a high-normal serum ionized calcium, suppresses serum parathyroid hormone levels. However, the dose required to control hyperphosphataemia may cause hypercalcaemia. We performed prospective studies in 50 previously undialysed patients starting CAPD (28 study group, 22 control group). Calcium carbonate was the only phosphate binder used in the study group which utilized a low calcium PD fluid (calcium 1.25 mmol/l), whilst the control group used standard PD solution (calcium 1.75 mmol/l) with calcium carbonate plus aluminium hydroxide phosphate binders as clinically indicated. The study group was able to take larger doses of oral calcium carbonate with no increase in episodes of hypercalcaemia compared to the control group. There were no instances of hypocalcaemia in any patient using the low-calcium dialysis fluid. Phosphate control was better in the study group, despite the additional use of aluminium-containing phosphate binders by some patients in the control group. Serum aluminium levels in the study group were maintained at < 11.5 mumol/l, but increased significantly in the control group from 3 months onward. Mean serum parathyroid hormone in the study group declined significantly from baseline values over the first 6 months, and remained at the lower level. Bone histology showed a tendency towards improvement over the 12 months, in terms of osteoclast numbers and activity. We conclude that using dialysis fluid with a reduced calcium concentration in compliant, well-monitored patients is safe.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of oral stable strontium to provide an index of intestinal calcium absorption in chronic ambulatory peritoneal dialysis patients.

Recent interest in the role of oral calcium carbonate and low calcium dialysate has emphasised the need for a simple, safe and inexpensive test of intestinal calcium absorption. The stable, non-radioactive, strontium absorption test fits these requirements. Stable strontium and calcium-45 were administered simultaneously to 19 fasting CAPD patients and their serum levels were subsequently measured. There was a close correlation between the absorption of calcium and strontium at both 60 and 120 min post-ingestion. The two markers resulted in the same classification of patients as normal or malabsorbers in 18 of 19 cases (95%), suggesting that strontium could be substituted for calcium-45 in a 60-min test of absorption enabling safe, simple and repeated measurements in renal failure patients.