Correction of metabolic acidosis with potassium citrate in renal transplant patients and its effect on bone quality.

BACKGROUND: Acidosis and transplantation are associated with increased risk of bone disturbances. This study aimed to assess bone morphology and metabolism in acidotic patients with a renal graft, and to ameliorate bone characteristics by restoration of acid/base homeostasis with potassium citrate. METHODS: This was a 12-month controlled, randomized, interventional trial that included 30 renal transplant patients with metabolic acidosis (S-[HCO(3)(-)] <24 mmol/L) undergoing treatment with either potassium citrate to maintain S-[HCO(3)(-)] >24 mmol/L, or potassium chloride (control group). Iliac crest bone biopsies and dual-energy X-ray absorptiometry were performed at baseline and after 12 months of treatment. Bone biopsies were analyzed by in vitro micro-computed tomography and histomorphometry, including tetracycline double labeling. Serum biomarkers of bone turnover were measured at baseline and study end. Twenty-three healthy participants with normal kidney function comprised the reference group. RESULTS: Administration of potassium citrate resulted in persisting normalization of S-[HCO(3)(-)] versus potassium chloride. At 12 months, bone surface, connectivity density, cortical thickness, and cortical porosity were better preserved with potassium citrate than with potassium chloride, respectively. Serological biomarkers and bone tetracycline labeling indicate higher bone turnover with potassium citrate versus potassium chloride. In contrast, no relevant changes in bone mineral density were detected by dual-energy X-ray absorptiometry. CONCLUSIONS: Treatment with potassium citrate in renal transplant patients is efficient and well tolerated for correction of metabolic acidosis and may be associated with improvement in bone quality. This study is limited by the heterogeneity of the investigated population with regard to age, sex, and transplant vintage.

Finding the right position: a three-year, single-center experience with the "self-locating" catheter.

BACKGROUND: Peritoneal dialysis (PD) catheter displacement is a major cause of dysfunction. Various catheter forms have been designed to improve outcome. One of them is based on the classical Tenckhoff catheter, but includes a small tungsten cylinder at the distal end to optimize location and to prevent dislocations. ♢ METHODS: In this retrospective study, we analyzed the functionality and complication profile of the self-locating catheter implanted at our center from November 2005 to September 2008 in our PD program. ♢ RESULTS: Data from 27 self-locating catheters implanted in 25 patients (12 women) were obtained. Patients were followed for up to 30 months (median observation time: 13 months), resulting in a cumulative study period of 357 PD months. A total of 22 complications were identified, including 1 episode of peritonitis per 52 patient-months, 1 tunnel infection, and 1 exit-site infection. The "functional catheter failure incidence rate" was approximately 0.01 catheters per month on PD (or approximately 1 catheter loss per 100 PD months). The catheter survival was 93% at 1 year. ♢ CONCLUSIONS: The "self-locating" PD catheter demonstrates low rates of catheter migration and dislocations, and good catheter survival.

Posttransplant acidosis and associated disorders of mineral metabolism in patients with a renal graft.

BACKGROUND: Persisting disturbances in acid/base homeostasis may have an impact on several metabolic aspects of individuals with a kidney graft, specifically with regard to mineral metabolism and bone. METHODS: We undertook a cross-sectional analysis among 823 unselected patients being transplanted with a functioning renal allograft who had at least one measurement of venous serum bicarbonate available within a 4-year period before May 1, 2005. As a determinate of metabolic acidosis bicarbonate was measured along with serum calcium, phosphate, parathyroid hormone, and other routine serological and epidemiological parameters. Data were assessed according to quartiles of serum bicarbonate and by univariate analysis. A multivariate regression model examined the effects of potential predictors of acidosis. RESULTS: Mean serum bicarbonate was 22.5+/-4 mmol/L, with 58.1% of the examined renal transplant patients having metabolic acidosis as defined by a venous bicarbonate of <24 mmol/L. Bicarbonatemia was highly associated with serum parathyroid hormone, phosphate, and calcium but also with renal graft function (determined as calculated glomerular filtration rate). Multiple stepwise regression analysis revealed age, glomerular filtration rate, parathyroid hormone, and albumin to be the strongest predictors of serum bicarbonate concentration. Therapy with any calcineurin inhibitor was not associated with an increased likelihood of acidosis (odds ratio 1.04), but a significant difference was found between cyclosporine A and tacrolimus, which had an attributed odds ratio for acidosis of 0.6 and 1.8, respectively. CONCLUSIONS: Metabolic acidosis is highly prevalent among an unselected cohort of renal transplant patients. A clear association exists between the severity of acidosis and disturbances of mineral metabolism. Thus, persisting acid/base disorders may accentuate bone disease in a setting with other factors predisposing for posttransplant osteopathy.