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Biomedical subjects

M Surian

Publications and source records attributed to M Surian.

At least 37 records · Page 2Linked to original sources
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

Abnormal red-cell calcium pump in patients with idiopathic hypercalciuria.

Idiopathic hypercalciuria is a common disorder whose inheritance suggests an enzyme abnormality in calcium transport. We measured calcium-magnesium-ATPase activity in erythrocytes from 38 patients (mean age [+/- SEM], 40 +/- 2.1 years) with idiopathic hypercalciuria (24-hour urinary calcium excretion greater than or equal to 0.1 mmol per kilogram of body weight) and a history of multiple calcium oxalate kidney stones. As compared with 41 healthy controls, the patients with hypercalciuria had increased erythrocyte-membrane calcium-magnesium-ATPase activity (64.2 +/- 2.19 vs. 51.6 +/- 1.91 nmol of ATP split per milligram per minute; P less than 0.01) and increased sodium-potassium pump activity (6866 +/- 233 vs. 6096 +/- 228 mumol of sodium per liter of red cells per hour; P less than 0.05). No significant difference between the two groups was found in erythrocyte sodium-potassium cotransport, sodium-lithium countertransport, or potassium content. In 66 patients with kidney stones (38 with hypercalciuria and 28 with normal calcium excretion), 24-hour urinary calcium excretion correlated with calcium-magnesium-ATPase activity (r = 0.46, P less than 0.001). Erythrocyte calcium-magnesium-ATPase activity remained unchanged in eight subjects studied after four months on a low-calcium diet. A study of 30 healthy families found significant correlations between mean values in parents and those in offspring for calcium-magnesium-ATPase (r = 0.68, P less than 0.001) and urinary calcium excretion (r = 0.45, P less than 0.02), with no significant correlations between parents with respect to these measures (r = 0.27 and r = 0.08, respectively). We conclude that abnormalities in erythrocyte calcium-magnesium-ATPase activity may represent an inherited defect in calcium transport related to the cause of idiopathic hypercalciuria.

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↗
PubMed1987

Pharmacological evaluation of urate renal handling in humans: pyrazinamide test vs combined pyrazinamide and probenecid administration.

Uricosuric and antiuricosuric drugs have been utilised widely for the study of tubular urate transport in humans. A normal suppression of urate excretion after pyrazinamide is usually taken as evidence of normal presecretory reabsorption. However, in patients with reduced presecretory reabsorption, during pyrazinamide inhibition of urate secretion unreabsorbed urate might still undergo reabsorption along postsecretory sites, allowing for a normal pyrazinamide suppression of urate excretion. To test this possibility, we have performed the pyrazinamide test both alone and after pretreatment with probenecid, which should block postsecretory urate reabsorption. The test was performed in 8 controls, in 9 patients with 'low-excretory' hyperuricaemia, and in 7 patients with tubular urate wasting. Pyrazinamide-non-suppressible urate excretion after pretreatment with probenecid did not differ from the excretion obtained after pyrazinamide alone in hyperuricaemic patients (mean difference 1.33 +/- 2.3% of filtered urate; P = NS); it was slightly higher in controls (3.4 +/- 3.4; P less than 0.05), but was much higher in patients with tubular urate wasting (19.6 +/- 12.7; P less than 0.005). The pyrazinamide test, performed alone, was normal in three patients with tubular urate wasting, but it was abnormal in all patients after pretreatment with probenecid. These results are consistent with the possibility that, during maximal pyrazinamide effect, some uric acid escaping reabsorption at presecretory sites may undergo reabsorption along postsecretory sites, leading to a quantitative overestimation of presecretory reabsorption. This phenomenon appears to have clinical relevance, especially in patients with abnormal urate reabsorption.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

The influence of dialysis fluid composition on dialysis tolerance.

To evaluate the role of bicarbonate loss through the dialyser and acetate flux to the patient in the development of symptoms during acetate dialysis, bicarbonate loss during acetate dialysis was prevented by using a combination of acetate and bicarbonate in the dialysate. Seven uraemic patients were treated for 4 months with acetate dialysis and, successively, for a similar period of time with bicarbonate, and a combination of acetate and bicarbonate dialysis. Blood-pressure drop and the incidence of hypotension and symptomatic episodes were similar in bicarbonate and combination dialysis, and significantly lower than in acetate dialysis. Serum acetate concentrations were similar during acetate and combination dialysis. These findings indicate that bicarbonate loss rather than the presence of acetate was responsible for the patients' intolerance to acetate dialysis.

Acetates↗
PubMed1987

Clinical evaluation of segmental tubular reabsorption of sodium and fluid in man: lithium vs free water clearances.

Segmental sodium reabsorption in the proximal and distal tubule was evaluated by different methods in seven healthy subjects, seven patients with recurrent calcium nephrolithiasis, five patients with isolated renal glucosuria and three patients with Fanconi syndrome. In all the subjects, the delivery of fluid from the proximal tubule, evaluated as 'chloride' factor during maximal water diuresis (DDCl, 12.4 +/- 5.5 ml/dl GFR), was lower (P less than 0.001) than 'volume' or 'chloride' factors during maximal water diuresis plus frusemide administration (40 mg i.v.) (Vf, 22.5 +/- 7.5 and DDClf, 27.1 +/- 8.9 ml/dl GFR, respectively), and of lithium clearance (FELi, 28.1 +/- 12.6%). Vf was lower than DDClf (P less than 0.001) and FELi (P less than 0.005), while DDClf and FELi did not differ; these unequal results are likely to represent different degrees of free water back-diffusion along distal tubule segments in the free water clearance studies. Accordingly, estimation of sodium reabsorption in the distal tubule showed corresponding differences within the four methods as those observed for the distal delivery: it was 25.5 +/- 12.2% when evaluated as [FELi-FECl]; 24.8 +/- 8.3 ml/dl GFR when evaluated as [CH2Of/GFR + delta FECl] (i.e. free water clearance during frusemide plus the frusemide-induced absolute increase in FECl); 19.5 +/- 6.7 ml/dl GFR (P less than 0.001 vs [FELi-FECl] and [CH2Of/GFR + delta FECl] when evaluated as [(CH2O + CH2OBD)/GFR] (i.e. CH2O before frusemide plus the frusemide-induced absolute increase in urine flow rate); and 10.0 +/- 4.8 ml/dl GFR when evaluated as CH2O (P less than 0.001 vs all the other evaluations).(ABSTRACT TRUNCATED AT 250 WORDS)

Furosemide↗
PubMed1987

The changes in plasma diffusible levels and renal tubular handling of magnesium during pregnancy: a longitudinal study.

Magnesium fasting plasma levels (total, PMg, and ultrafiltrable, PMgUF), daily urinary excretion and tubular reabsorption in the fasting state were measured in 14 healthy women along an uncomplicated gestation and compared with the values observed 3-6 months after delivery (C). PMg and PMgUF progressively fell during gestation (from 1.96 +/- 0.14 and 1.38 +/- 0.09 mg/dl in C, respectively, to 1.67 +/- 0.13 (P less than 0.0005) and 1.2 +/- 0.09 (P less than 0.0005) after 17-26 weeks of gestation and to 1.66 +/- 0.10 (P less than 0.0005) and 1.17 +/- 0.08 (P less than 0.0005) after 27 weeks to term). The decrease in PMg and PMgUF was further apparent in an additional group of 46 pregnant women in comparison with 20 sex-matched non-pregnant controls. Urinary Mg excretion remained unchanged throughout gestation, as did glomerular filtered load of PMgUF and tubular Mg reabsorption in the fasting state, due to the increase in GFR. Moreover, urinary Mg excretion per unit GFR (MgE, mg/dlGFR) and fractional excretion of MgUF filtered load (FEMgUF, %) fell (from 41 +/- 25 and 3.0 +/- 0.9 in C, respectively, to 26 +/- 12 (P less than 0.01) and 2.2 +/- 1.0 (P less than 0.05] in the last period, indicating that a greater fraction of filtered Mg was being reabsorbed by renal tubules. There was a significant inverse correlation between PMgUF and GFR in all the periods studied (r = 0.39, P less than 0.025).(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗