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Biomedical subjects

F Malberti

Publications and source records attributed to F Malberti.

At least 37 records · Page 2Linked to original sources
PubMed1993

Calcium mass transfer and kinetics in CAPD using calcium-free solutions.

In 12 continuous ambulatory peritoneal dialysis (CAPD) patients we evaluated peritoneal calcium mass transfer (CaMT), serum and effluent dialysate ionized calcium (iCa) changes, and the variations of the dialysate-to-plasma (D/P) ratio for calcium throughout 6-hour dwell exchanges with zero calcium, 1.25 mmol/L calcium (1.25 Ca), and 1.75 mmol/L calcium (1.75 Ca) peritoneal solutions. The infused ionized and total calcium were, respectively, 1.28 +/- 0.04 and 1.77 +/- 0.04 mmol/L with 1.75 Ca and 0.89 +/- 0.03 and 1.28 +/- 0.04 mmol/L with 1.25 Ca solutions. During CaMT studies, the ultrafiltration rate was 250 mL on average, and serum iCa 1.24 mmol/L. Calcium was gained by the patients (+0.41 +/- 0.6 mmol/L) using standard solutions. CaMT was -0.67 +/- 0.4 mmol/L with 1.25 Ca and -2.4 +/- 0.4 mmol/L with zero Ca solutions. Throughout the exchanges the D/P ratio for iCa decreased from 0.97 +/- 0.03 at 0 minutes to an equilibrium value (at about 240 minutes) of 0.84 +/- 0.03 with 1.75 Ca solutions, while it increased from 0.75 +/- 0.04 to 0.83 +/- 0.05 with 1.25 Ca solutions. After a 6-hour exchange with zero Ca, the D/P ratio for iCa was 0.76 +/- 0.04, significantly lower than the D/P ratio for urea (0.97 +/- 0.02), creatinine (0.89 +/- 0.06), and bicarbonate (0.98 +/- 0.02). In conclusion, dialysate and serum iCa are in equilibrium at a D/P ratio of about 0.84. Thus calcium is gained by the patients using 1.75 Ca solutions, and it is lost (both by diffusion and ultrafiltration) using 1.25 Ca solutions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Improvement of secondary hyperparathyroidism and reduction of the set point of calcium after intravenous calcitriol.

In this study we evaluated the effect of intravenous calcitriol on parathyroid function and ionized calcium/PTH sigmoidal curve obtained during low and high calcium hemodialysis in 10 patients with osteitis fibrosa whose secondary hyperparathyroidism was refractory to conventional therapy. After four months of intravenous calcitriol, serum ionized calcium increased from 1.28 +/- 0.08 to 1.37 +/- 0.11 mmol/liter (P < 0.001), serum phosphate from 1.54 +/- 0.18 to 1.79 +/- 0.4 mmol/liter (P = NS), serum calcitriol from 16.7 +/- 9.9 to 34.3 +/- 6.4 pg/ml (P < 0.001), while alkaline phosphatase decreased from 366 +/- 340 to 226 +/- 180 IU/liter (P < 0.05), osteocalcin from 46.4 +/- 20 to 34.5 +/- 15.3 ng/ml (P < 0.05) and basal intact PTH from 1069 +/- 700 to 305 +/- 270 (P < 0.01). Basal PTH started to decrease after one month of treatment prior to the increase in the ionized calcium. Because of hypercalcemia, the dialysate calcium was decreased from 1.75 to 1.5 mmol/liter in three of five patients on hemodialysis and calcium-containing solutions were substituted by calcium-free replacement fluids in four of five patients on hemodiafiltration. Calcitriol dose at the first month of therapy was 5.6 +/- 0.8 micrograms/week, but successively it was decreased because of hypercalcemia to a final dose of 3.6 +/- 1.3 micrograms/week. After intravenous calcitriol the ionized calcium/PTH sigmoidal curve shifted to the left and downward. Maximally stimulated PTH and maximally inhibited PTH obtained during low and high calcium dialysis significantly decreased as did the ratio of basal PTH/PTHmax and the set point of calcium.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcitriol↗
PubMed1993

Computerized management of peritoneal dialysis.

The importance of the evaluation of dialytic adequacy is well known in peritoneal dialysis. It is necessary to be able to quantify and individualize the substitution treatment. In 15 patients we compared five quantitative approaches by using original software: Teehan's dialysis index (DI); Diaz-Buxo's liters/week (LW); Keshaviah's the quantity of dialysis prescribed (wKt/V); and Boen and Twardowski's weekly creatinine clearance (WC). All patients were treated by continuous ambulatory peritoneal dialysis (CAPD) according to the peritoneal equilibration test (PET). Peritoneal solute clearances for urea, creatinine, uric acid, and phosphorus were adequate, but there was disagreement between adequacy indexes. According to the DI, 40% of our patients were underdialyzed, 33% were adequate, and 27% received excessive dialytic dose, while according to LW and wKt/V, about 50% were adequate, 10% underdialyzed, and 40% received excessive doses. According to WC, 74% were overdialyzed and 26% were adequate. In two patients only (13%) all the indexes indicated underdialysis. We think that the DI is too severe an adequacy index, probably because residual renal clearances have a great weight in the formula, while WC may lead to an overestimate of the actual dose of therapy in patients with significant residual renal clearance. Prospective, randomized and clinical studies are needed to better assess the optimal index for individualization of targeted peritoneal dialysis prescription.

Creatinine↗
PubMed1993

The sigmoidal parathyroid hormone-ionized calcium curve and the set point of calcium in hemodialysis and continuous ambulatory peritoneal dialysis.

A high incidence of adynamic bone disease not related to aluminum intoxication has been reported in continuous ambulatory peritoneal dialysis (CAPD). Since reduced parathyroid hormone (PTH) secretion may predispose to adynamic bone, we investigated whether parathyroid gland sensitivity may be depressed in CAPD in comparison with hemodialysis (HD). Thus we determined parathyroid function by the evaluation of the PTH-ionized calcium (ICa) relationship, which was obtained inducing hypocalcemia and hypercalcemia in 19 CAPD and 18 HD patients with biochemical and histological evidence of mild (MILD) or severe (OF) hyperparathyroidism, but negative stainable bone aluminum. Either CAPD or HD patients with OF showed a shift to the right of the sigmoidal PTH-ICa curve in comparison with patients with MILD, greater set point of calcium, and maximal PTH stimulation and inhibition. The PTH-ICa curve and the other parathyroid function parameters were not different in CAPD and HD patients within the same bone histological group. In conclusion, our data document that parathyroid gland activity is stimulated either in CAPD and HD patients with OF, but is not depressed in CAPD patients in comparison with HD patients.

Calcium↗
PubMed1992

Effect of chronic intravenous calcitriol on parathyroid function and set point of calcium in dialysis patients with refractory secondary hyperparathyroidism.

This study evaluates the effect of intravenous calcitriol on parathyroid function and ionized calcium-PTH sigmoidal curve obtained during low- and high-calcium haemodialysis in 10 patients with osteitis fibrosa whose secondary hyperparathyroidism was refractory to conventional therapy. After 4 months of intravenous calcitriol, serum ionized calcium increased from 1.28 +/- 0.08 to 1.37 +/- 0.11 mmol/l (P less than 0.001), serum phosphate from 1.54 +/- 0.18 to 1.79 +/- 0.4 mmol/l (P NS), serum calcitriol from 16.7 +/- 9.9 to 34.3 +/- 6.4 pg/ml (P less than 0.001), while alkaline phosphatase decreased from 366 +/- 340 to 226 +/- 180 IU/l (P less than 0.05), osteocalcin from 46.4 +/- 20 to 34.5 +/- 15.3 ng/ml (P less than 0.05), and basal intact PTH from 1069 +/- 700 to 305 +/- 270 (P less than 0.01). Basal PTH started to decrease after 1 month of treatment prior to the increase in the ionized calcium. Because of hypercalcaemia the dialysate calcium was decreased from 1.75 to 1.5 mmol/l in three of five patients on haemodialysis, and calcium-containing solutions were replaced by calcium-free fluids in four of five patients on haemodiafiltration. Calcitriol dose, at the first month of therapy was 5.6 +/- 0.8 micrograms/week, but it was successively decreased because of hypercalcaemia to a final dose of 3.6 +/- 1.3 micrograms/week. After intravenous calcitriol the ionized calcium-PTH sigmoidal curve shifted to the left and downward. Maximally stimulated PTH and maximally inhibited PTH obtained during low- and high-calcium dialysis significantly decreased, as well as the ratio of basal PTH/PTHmax and the set point of calcium.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcitriol↗
PubMed1991

Effect of hemodialysis and hemodiafiltration on uremic neuropathy.

This study was undertaken to compare the effect of 1 year hemodialysis (HD) or hemodiafiltration (HDF) treatment on peripheral neuropathy. Thus 21 of 42 patients on chronic HD (1-1.3 m2 cuprophane dialyzer, Qb 300 ml/min) were switched to HDF (1.3 m2 polysulfone dialyzer, Qb 400 ml/min, substitution volume 9-13 liters, ultrafiltration rate 60-70 ml/min), while the remaining patients were considered as a control group. Treatment time was scheduled both in HD and HDF to maintain adequate BUN levels in relation to protein catabolic rate. However, HDF provided a significantly greater weekly inulin (MW 5,000) clearance than HD (5.8 +/- 1.2 vs. 1.6 +/- 0.2 ml/min; p less than 0.001). HD and HDF groups were comparable for age, time on dialysis and starting electroneurographic parameters, which were on average within the normal range. After 1 year follow-up, creatinine, hematocrit, calcium, phosphate, PTH, BUN, protein catabolic rate and residual GFR were comparable in the two groups, whereas beta 2-microglobulin was significantly reduced in HDF patients (29 +/- 6.7 vs. 38.8 +/- 13.9 mg/l in HD patients, p less than 0.01). During the 1-year treatment, electroneurographic parameters did not change in HDF patients, whereas a significant decrease of ulnar motor nerve conduction velocity, ulnar muscle action potential amplitudes, median sensory nerve conduction velocity and peroneal muscle action potential amplitudes was detected in HD patients. We conclude that HDF might prevent the worsening of the electroneurographic indices occurring during chronic HD treatment, as it provides a more effective removal of middle and larger molecules than HD. The use of a more biocompatible membrane in HDF might further contribute to this favorable effect on uremic neuropathy.

Adult↗
PubMed1991

Ionised calcium changes and parathyroid hormone secretion in haemodiafiltration in relation to substitution fluid calcium content.

This study was carried out to evaluate the acute effect of either 1.75 mmol/l calcium (A-HDF) or bicarbonate-containing and calcium-free (B-HDF) substitution fluid on calcium balance, serum ionised calcium, and intact parathyroid hormone (PTH) during haemodiafiltration (HDF: 1.3 m2 polysulphone dialyser; blood flow rate, 400 ml/min; treatment time 210 min; substitution fluid volume, 10 litres; dialysate calcium, 1.75 mmol/l). During A-HDF calcium balance was slightly positive (1.47 +/- 2.95 mmol), serum ionised calcium increased from 1.24 +/- 0.08 mmol/l to a final 1.46 +/- 0.05 mmol/l at the end of the treatment (P less than 0.001), and PTH decreased from 227 +/- 231 pg/ml to 150 +/- 123 pg/ml (P less than 0.01), during B-HDF calcium balance was negative (-3.06 +/- 1.3 mmol), ionised calcium decreased from 1.29 +/- 0.05 to 1.24 +/- 0.05 mmol/l (P less than 0.05) without inducing a statistically significant increase in PTH. However, in some patients the increase in PTH after treatment was greater than 50%. When the ultrafiltration rate was increased to 75-100 ml/min and bicarbonate-containing and calcium-free replacement fluid was used (B2-HDF), calcium balance became more negative (-9.75 +/- 4.55 mmol) and the decrease of ionised calcium was greater (from 1.3 +/- 0.06 to 1.14 +/- 0.04 mmol/l, P less than 0.01) inducing a significant increase of PTH (from 297 +/- 366 to 443 +/- 518 pg/ml, P less than 0.01). PTH changes were negatively correlated (r = -0.85) to ionised calcium changes during the treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Bicarbonates↗
PubMed1989

Effects of acute administration of acetazolamide and frusemide on lithium clearance in humans.

To investigate the mechanism(s) of acute frusemide-induced increases in FELi, the effects of frusemide and acetazolamide, the carbonic anhydrase inhibiting agent, were evaluated in 19 healthy subjects either before or after pretreatment with acetazolamide or frusemide (11 subjects and eight subjects respectively). Acetazolamide pretreatment did not modify frusemide-induced increases in FELi (delta FLi 12.8 +/- 4.1% compared to 14.6 +/- 7.3%, P = NS); similarly, frusemide pretreatment did not modify acetazolamide-induced increases in FELi (delta FLi: 11.3 +/- 5.9% compared to 9.8 +/- 3.8%, P = NS). Acetazolamide-induced changes of FELi were correlated significantly with acetazolamide-induced increases of FEHCO3 (r = 0.61, P less than 0.05), FENa (r = 0.46, P less than 0.05) but not of FECl (r = 0.25, P = NS). On the other hand, frusemide-induced changes of FELi were correlated significantly with frusemide-induced increases of FENa (r = 0.62, P less than 0.005), FEC1 (r = 0.52, P less than 0.025) but not of FEHCO3 (r = 0.3, P = NS). Thus, frusemide effects on tubular lithium reabsorption are not related to carbonic anhydrase inhibition; furthermore, it appears that frusemide and acetazolamide affect lithium reabsorption by different and independent mechanism(s), possibly acting at different nephron site(s).

Acetazolamide↗
PubMed1989

Adequacy of haemodiafiltration.

In this study we have evaluated the influence of blood and ultrafiltration flow rate on the performance of five different high-flux membrane dialysers during haemodiafiltration. On the basis of clearance data we optimised the haemodiafiltration schedule of six uraemic patients to maintain an adequate midweek blood urea nitrogen concentration, while reducing the treatment time from 285 +/- 23 min to 210 min. After a follow-up of 6 months, we observed no difference in the clinical tolerance or in the biochemical parameters, compared to those found during the preceding haemodialysis period. Our data confirm the suggestions of other authors that haemodiafiltration is an effective alternative to conventional haemodialysis.

Adult↗
PubMed1988

Efficacy and safety of long-term treatment with calcium carbonate as a phosphate binder.

The efficacy and safety of calcium carbonate as a phosphate binder was evaluated in 20 patients on chronic hemodialysis who had previously received aluminum hydroxide. During the control period the patients were on aluminum hydroxide and calcitriol therapy and had plasma phosphorus levels less than 6 mg/dL (4.95 +/- 0.8 mg/dL). Aluminum hydroxide was then discontinued and no phosphate binder was prescribed for 1 month. Every patient developed hyperphosphatemia so that calcium carbonate treatment was begun and calcitriol dose was adjusted in relation to plasma calcium changes. After 24 months of calcium carbonate therapy, plasma phosphorus was 4.85 +/- 0.7 mg/dL, using a daily dose of calcium carbonate of 2.57 +/- 1.3 g (range, 1 to 6 g). The daily dose per patient of calcitriol was not different from that prescribed during the control period, but in five patients calcitriol was permanently withdrawn for hypercalcemia. At the end of the study plasma calcium, magnesium, bicarbonate, alkaline phosphatase, and parathyroid hormone values were unchanged in comparison with the control period, whereas a significant reduction in plasma aluminum and plasma aluminum increase induced by deferoxamine infusion was observed. The frequency of hypercalcemic and hyperphosphatemic episodes during the last 12 months of calcium carbonate therapy (6.2% and 16.6%, respectively) was not different from that observed during the 12 months on aluminum hydroxide therapy preceding the control period (4.5% and 14.7%, respectively). It was concluded that calcium carbonate is effective in the control of hyperphosphatemia and secondary hyperparathyroidism in patients on chronic hemodialysis and that the incidence of hypercalcemia is low when the daily dosage is less than 6 g.

Adult↗