Physical activity in chronic kidney disease: a plausible approach to vascular calcification?

Vascular calcification (VC) is a prominent feature that affects up to 40 to 80% of Chronic Kidney Disease (CKD) patients depending on the degree of renal impairment. Though etiology and pathogenesis of the different types of VC are far from being elucidated, it is conceivable that an imbalance between promoters and inhibitors represents the condition that triggers VC deposition and progression. In addition to traditional cardiovascular risk factors, several lines of evidence suggest that specific factors may affect the arterial system and prognosis in CKD. Over the last decade, a few pharmacological strategies aimed at controlling different selected risk factors for VC have been investigated yielding conflicting results. In light of the complicated interplay between inhibitors and promoters as well as the fact that VC represents the result of cumulative and prolonged exposure to multiple risk factors, a more comprehensive risk modification approach such as lifestyle modification or physical activity (PA) may represent a valid strategy to attenuate VC deposition and progression.We herein aim at reviewing the rationale and current evidence on the potential for lifestyle modification with a specific focus on PA as a cost-effective strategy for VC treatment.

[The Italian Registry of Vascular Access]

The Vascular Access Study Group of Italian Society of Nephrology has designed a National Register in order to create an archive that collects the data on vascular accesses more detailed than the mere indication of arteriovenous fistula with native vessels, prosthetic fistula and central venous catheter. The obstacles to such a project are represented by the absence of "uniformity" in the name of the arterovenous fistula, the difficulty in increasing the daily work of dialysis centers with another registry and finally by privacy concerns. In order to standardize the vascular accesses name the Study Group proposal is to eliminate any denomination and adopt a code-descriptive system, indicating the seat of the anastomosis (1/3 distal, middle and proximal forearm, arm or lower limb), the limb (if dominant or non-dominant), the vessels involved, the type of anastomosis and the number of interventions that the pt has undergone including the last one. In this way, uniformity and universality are guaranteed. Every aspect scribed will be a cell of a data base and can used to statistical analysis. The study group has set up a software (Gev@) in order to facilitate data storage. The software is based on a form compiled at the end of each surgical procedure. The form will then be archived in digital format thereby generating automatically the data base. The advantage of this system, is represented by the possibility of turning a routine medical procedure, namely the recording of a surgical procedure, in a data base exportable for the creation of the register. As regards the issue of privacy will be obtained the patient's consent to the processing of data and the register will be stored and managed according to the regulations in terms of privacy. In the coming months, after a time of testing, the software will be available to each italian dialisys center.

[SLED v CRRT: the choice between a Rolls and a Ferrari?]

Although several advantages have been attributed to continuous renal replacement therapy (CRRT), including greater hemodynamic stability permitting better fluid removal, improved recovery of renal function, and more efficient removal of small and large metabolites, none of these factors has been adequately corroborated in controlled trials. On the other hand, sustained low efficiency dialysis (SLED) has enjoyed an unsurpassed renaissance over the last decade for treatment of severely ill patients with acute kidney injury in the intensive care unit (ICU). SLED combines excellent detoxification and good cardiovascular tolerability for even severely ill patients in the ICU. SLED also provides good treatment time flexibility at lower costs than CRRT with the advantage that existing dialysis systems can be used. In conclusion, SLED represents an alternative to CRRT, enabling optimal treatment of complex critically ill patients. It can be considered a key treatment modality for patients on ICU, giving nephrologists and ICU physicians the opportunity for pooling their twin areas of expertise.

[A technique for inserting inadvertently removed tunneled hemodialysis catheters through the original exit site]

Accidental loss of tunneled hemodialysis (HD) central venous catheters (CVCs) is a rare complication. In the absence of other sites available for positioning a new CVC, the lack of a vascular access exposes the patient to a high risk of mortality. The technique for inserting inadvertently removed tunneled CVCs using the original exit site has never gained popularity and has been used, although with good results, in selected cases only. The purpose of this case report is to describe our experience in similar cases, and to propose a variant of the procedure described above: in 4 cases occurring over the last 12 months, our technique permitted recovery of vascular access for up to 72 hours after the loss of the CVC, with placement of a new cuffed CVC performed in the space of a few minutes. There were no cases of bleeding nor episodes of infection. The patients resumed their regular HD program with adequate performance of the CVC during a follow-up period that ranged from 3 to 12 months.In conclusion, we believe that this simple manoeuvre can help the nephrologist solve one of the dialysis room's moments of genuine emergency.

Effect of dialysate calcium concentrations on parathyroid hormone and calcium balance during a single dialysis session using bicarbonate hemodialysis: a crossover clinical trial

BACKGROUND

In bicarbonate-based hemodialysis, dialysate total calcium (tCa) concentration may have effects on mineral metabolism.

STUDY DESIGN

Randomized crossover trial of 3 dialysate tCa concentrations (2.5, 2.75, and 3.0 mEq/L).

SETTING & PARTICIPANTS

22 stable anuric uremic patients underwent three 4-hour bicarbonate hemodialysis sessions with the 3 different dialysate tCa concentrations using a single-pass batch dialysis system.

OUTCOMES

Hourly measurements of plasma water ionized calcium (iCa) and plasma parathyroid hormone (PTH) concentrations. tCa mass balances were measured from the dialysate side.

RESULTS

Hourly plasma water iCa concentrations were higher with a dialysate tCa concentration of 3.0 compared with 2.75 and 2.5 mEq/L (P < 0.05), as were iCa concentrations at the end of dialysis sessions (2.66 ± 0.1, 2.56 ± 0.12, and 2.4 ± 0.08 mEq/L, respectively; P < 0.001). Mean tCa mass balance values (diffusion gradient from the dialysate to the patient) were positive with all dialysate tCa concentrations and increased progressively with dialysate tCa concentration (75 ± 122, 182 ± 125, and 293 ± 228 mg, respectively; P < 0.001). Plasma PTH levels increased during dialysis using dialysate tCa concentration of 2.5 mEq/L (mean increase, 225 ± 312 pg/mL) and decreased with dialysate tCa concentrations of 2.75 and 3.0 mEq/L (mean decreases, 68 ± 325 and 99 ± 432 pg/mL, respectively).

LIMITATIONS

Small sample size and lack of measurement of total-body calcium mass balances.

CONCLUSIONS

A dialysate tCa concentration of 2.75 mEq/L might be preferable to 2.5 or 3.0 mEq/L because it is associated with mildly positive tCa mass balance values, plasma water iCa levels in the reference range, and stable PTH levels during dialysis.

Serum parathyroid hormone and phosphate influence the levels of circulating CD34+ cells in uremia

BACKGROUND

Parathyroid hormone (PTH) is an active stimulator of bone marrow osteoblasts; it is involved in the niche organization, ie the bone marrow microenvironment which controls the turnover and the fate of endothelial progenitor cells (EPCs). PTH stimulates EPC production; this action can be measured by counting the number of circulating CD34+ cells.

METHODS

This observational cross-sectional study aimed to verify this effect in 3 groups of hemodialysis patients with different serum PTH levels. The first group consisted of 11 patients affected by secondary hyperparathyroidism (SHPTH group, serum PTH levels >500 pg/ml); the second group consisted of 10 patients with serum PTH levels between 150 and 500 pg/ml (TargetPTH group); the third group consisted of 10 patients with serum PTH levels below the treatment target after parathyroidectomy (PTx group, serum PTH levels <150 pg/ml). Serum PTH, calcium (Ca), phosphorus (P), alkaline phosphatases (ALP), urea nitrogen, albumin and hemoglobin were measured. Flow cytofluorimetry with CD45+ sequential gating was effected; therefore, CD34+ cells could be analyzed.

RESULTS

The SHPTH group showed significantly higher values of serum PTH, P and ALP (respectively, p<0.0001, p<0.033 and p<0.0001), and significantly lower values of circulating CD34+ cells (both in absolute and percent terms) in the SHPTH and in the TargetPTH groups (for both, p<0.0001). Two models of multiple regression analysis built with circulating CD34+ cells (expressed as percentage in the first one and as absolute values in the second one) as dependent variables showed that only serum PTH and P values were inversely associated with both.

CONCLUSIONS

Our data suggest that an inverse relationship exists in uremic patients among circulating CD34+ cells and serum P and PTH levels. The count of circulating CD34+ cells might represent a novel biomarker for the assessment of the cardiovascular risk for dialysis patients.

[Uremic toxins: the case of protein-bound compounds]

Uremic retention solutes, if biologically or biochemically active, are called ''uremic toxins''. The retention of these solutes has a negative impact on many functions of the organism, particularly the cardiovascular system. The classification which is applied today is based on the kinetic behavior of the uremic retention solutes during dialysis: 1) small water-soluble molecules (< 500 Daltons); 2) middle molecules (> 500 Daltons); 3) protein-bound compounds. The latter are the object of the present review. The most important among them are p-cresol, p-cresyl sulfate, homocysteine, phenols, and indoles. No interventional studies are currently available that show the effect of an improvement in the removal of protein-bound compounds on patient outcomes, simply because most of the alternative dialysis strategies proposed so far are not superior to standard dialysis in removing protein-bound compounds. The question as to how to improve the removal of these solutes therefore remains unanswered. Alternative strategies might include adsorption therapies, either administered orally or during the extracorporeal treatment. In conclusion, the uremic syndrome is a complex clinical entity which involves a large number of retention solutes, many more than the small water-soluble molecules. Dialysis strategies should therefore aim to remove not only urea but also retention solutes, mainly because middle and protein-bound molecules appear to be correlated more frequently with deleterious biological, biochemical and clinical effects.

A new index of hemodialysis adequacy: clearance x dialysis time / bioelectrical resistance

BACKGROUND

Kt/V urea was established as an index of hemodialysis (HD) adequacy. The use of V urea (as derived by the Watson et al formulae) as a normalizing factor has been questioned, and alternative parameters such as body weight 0.67 (W 0.67), body surface area (BSA), resting energy expenditure (REE), high metabolic rate organ (HMRO) mass and liver size (LV) have been proposed (respective HD adequacy indices: Kt/W 0.67, Kt/BSA, Kt/REE, Kt/HMRO and Kt/LV).

METHODS

The present study aimed to calculate the 6 previously described normalizing factors (all obtained utilizing anthropometric variables) and to measure bioelectrical resistance (R), an independent and directly achievable biological parameter, in 481 white, disease-free individuals and 270 white prevalent HD patients, pair-matched by age, body weight and height, after stratification by sex. Further, we aimed to evaluate the effect of substituting BSA, W 0.67, REE, HMRO, LV and R for V urea as denominator in Kt/V urea on the distribution of target dialysis dose in a cohort of 1,058 white prevalent HD patients. All individuals underwent 1 single-frequency bioelectrical impedance measurement, on the nondominant side of the body, injecting 800 μA at 50 kHz alternating sinusoidal current with a standard tetrapolar technique.

RESULTS

When comparing pair-matched disease-free men and women with HD men and women, respectively, only R was statistically significantly different (p<0.0001 and p<0.02, respectively). As expected, V urea, BSA, W 0.67, REE, HMRO and LV were not significantly different in both comparisons. Furthermore, equivalent Kt/R for a range of prescribed Kt/V urea was able to give a more clearcut differentiation among sexes and body sizes, when compared with the other methods for scaling dialysis dose.

CONCLUSIONS

BSA, W 0.67, REE, HMRO and LV, as well as V urea are derived by means of calculations which utilize anthropometric variables. In contrast, R is a biological parameter which can be directly measured in the clinical setting by means of a simple, low-cost, fast and repeatable procedure. Even though Kt/R is probably the most appropriate method for scaling dialysis dose among those evaluated in the present study, further work is required to develop these concepts and translate them into rigorous outcome-based adequacy targets suitable for clinical usage.

A simple approach for assessing equilibrated Kt/V beta 2-M on a routine basis

BACKGROUND

Large observational studies have shown a reduction in morbidity and mortality in patients on high-flux haemodialysis (HD) or convective techniques, compared with low-flux HD. An index to evaluate treatment efficiency in middle molecule (MM) removal would be recommended. Since beta-2-microglobulin (beta2-M) is a recognized MM marker, we evaluated an easy approach for Kt/V(beta2-M) assessment on a routine basis, avoiding other complex methods.

METHODS

An equation that estimates single-pool (sp) Kt/V(beta2-M) was derived from Leypoldt's formula, which calculates beta2-M dialyser clearance (K(beta2-M)) from the post/pre-dialysis beta2-M concentration (C(t)/C(0)) ratio and the weight loss/end-dialysis weight (Delta W/W) ratio. Our equation, spKt/V(beta2-M) = 6.12 Delta W/W [1 - ln(C(t)/C(0))/ln(1 + 6.12 Delta W/W)], was derived by assuming urea distribution volume (V(u)) as 49% of W and beta2-M volume (V(beta2-M)) as V(u)/3, in agreement with the average patient values in the HEMO Study. The spKt/V(beta2-M) values calculated with our equation (F) in 129 patients on 407 sessions of different high-flux treatments were compared with those calculated with the method applied in the HEMO Study (HM). Equilibrated beta2-M concentration (C(eq)) of the same sessions was also estimated with the equation for C(eq) by Tattersall, and equilibrated Kt/V (eKt/V(beta2-M)) was calculated by introducing Tattersall's equation into our simplified spKt/V(beta2-M) formula.

RESULTS

Mean results of our spKt/V(beta2-M) equation (F) were very close to those of the HM method (1.48 +/- 0.38 vs 1.47 +/- 0.37). The difference was less than +/-0.1 in 95% of cases. A mean end-session beta2-M rebound of 44 +/- 14% was predicted, which caused a mean reduction in actual Kt/V(beta2-M) of ~27% (eKt/V(beta2-M) = 1.08 +/- 0.26).

CONCLUSIONS

The method proposed to estimate spKt/V(beta2-M) and eKt/V(beta2-M) could become a simple tool to monitor the efficiency of high-flux HD and convective techniques and to evaluate the adequacy of treatments in terms of MM removal. Moreover, it might help to better understand the effects of different dialysis schedules. Validation on a larger dialysis population is required.

Vitamin D treatment in hemodialysis patients with low serum levels of parathyroid hormone: which is the best choice?

BACKGROUND

This short-term prospective study aimed to assess the effects of treatment with calcidiol (25-hydroxycholecalciferol) or calcitriol in the subset of hemodialysis patients characterized by stable low serum levels of parathyroid hormone (PTH) or affected by hypoparathyroidism after total parathyroidectomy (PTx).

METHODS

Two groups were created according to baseline serum levels of 25-hydroxyvitamin D (25(OH)D): group A (12 patients): <15 ng/mL; group B (12 patients): >15 ng/mL. They underwent a 6-month treatment with oral calcidiol (group A) or oral calcitriol (group B).

RESULTS

Group A showed a statistically significant increase in the serum levels of calcium corrected for serum albumin (cCa), phosphorus (P), total alkaline phosphatases (ALP), PTH and 25(OH)D. Group B showed a statistically significant increase in serum levels of cCa and P. A statistically significant decrease in serum levels of ALP and 25(OH)D was observed. Baseline serum 25(OH)D levels were 12.6 + 3.8 ng/mL in group A and 23.0 + 5.0 ng/mL in group B (p<0.0001). After 6 months, they increased to 38.3 + 21.0 ng/mL in group A (p<0.01) and decreased to 16.9 + 5.8 ng/mL in group B (p<0.01).

CONCLUSIONS

Treatment with oral calcitriol was associated with a decrease in the serum levels of ALP and 25(OH)D; treatment with oral calcidiol was associated with more physiological serum levels of 25(OH)D and with an increase in the serum levels of ALP and PTH: whether the statistically significant differences in the biochemical parameters achieved with the 2 treatments have a clinical relevance, remains a matter of debate.

Simvastatin-induced myoglobinuric acute kidney injury following ciclosporin treatment for alopecia universalis

Alopecia areata can affect the entire scalp (alopecia totalis) or cause loss of all body hair (alopecia universalis). Ciclosporin (CsA) has been suggested for its treatment, with controversial results. Concomitant use of statins and CsA may increase the risk of rhabdomyolysis due to drug–drug interactions.

Here we report the case of a 45-year-old woman treated with CsA for alopecia universalis, who presented a severe myoglobinuric acute kidney injury following the concomitant use of simvastatin. Upon admission to our unit, she was oligo-anuric. Her serum creatinine level was 13.8 mg/dl. CsA and simvastatin therapy were stopped, and haemodialysis treatment was started (eight daily dialysis sessions) until sufficient kidney function was regained. After 1 month, her serum creatinine level was 3.5 mg/dl; after 2 months and onwards (follow-up of 4 months), her serum creatinine level was 1.4 mg/dl and creatinine clearance was 43.2 ml/min.

In conclusion, physicians should be aware of the potential risks of the combined use of CsA and statins. Patients should be advised to report any muscle symptoms when they are on statins and CsA. The laboratory follow-up should include the monitoring of serum creatinine and muscle enzyme levels, blood CsA levels and liver function tests.

[Management of central venous catheter: prevention of thrombosis and bacteremia]

The use of central venous catheters (CVC) as vascular access has increased considerably in recent years, especially because of the progressive aging and increasingly severe comorbidities of the dialysis population. The main factors limiting the long-term use of a hemodialysis catheter are thrombosis and infection. Thrombosis can be treated with thrombolytic agents and prevented effectively by means of anticoagulants. CVC infections represent the main cause of morbidity and mortality in these patients. This is the reason why systemic antibiotic therapy must be started very rapidly, based even on a simple clinical suspicion and in the absence of any confirmation of bacteremia. If antibiotic therapy fails, the CVC must be removed. The recent introduction of antibiotic lock therapy appears to be an effective means to prevent bacteremia. However, it must not be forgotten that the best way of preventing CVC-related bacteremia is by reinforcing all control procedures, with the active involvement of patients and staff.

[A particular case of hemodialysis with a single-pass batch system]

The GENIUS 90 Therapy System (GENIUS) (Fresenius Medical Care, Bad Homburg, Germany) is a mobile dialysis machine with a 90-liter, thermally insulated glass tank. Fresh dialysis fluid is prepared by mixing sterile ingredients (electrolytes and glucose) with preheated ultrapure water. Here we report the case of a 60-year-old hemodialysis patient who was hospitalized in our unit in November 2005 because of an ischemic stroke affecting the left temporal-parietal-occipital region of the brain. The persisting clinical features included right hemiplegia, motor aphasia, epilepsy and stage I coma. The patient started thrice-weekly GENIUS hemodialysis treatment (about 270 sessions to date) in his hospital room with no continuous nursing assistance. In conclusion, GENIUS is able to offer user-friendly, high-quality and adequate dialysis treatment.

[We should strive for optimal hemodialysis: treatment time is the key factor]

Nephrologists should strive for optimal hemodialysis. Convection, at least as it is conceived today, is far from optimal and the same is true of standard bicarbonate dialysis. A very recent paper by Eloot et al (Kidney Int 2008: 73: 765-70) clearly illustrates the way towards optimal hemodialysis by showing in a simple and intelligent manner the independent effect of the factor time on the adequacy of hemodialysis. Furthermore, it simplifies the conceptual scenario of dialysis adequacy and points to diffusion mechanisms as the key modality to remove uremic retention solutes. Thus, it is clear that we should strive for longer and/or more frequent dialysis sessions. Long nocturnal home hemodialysis every other night appears to be more appealing to patients than 5 to 7 dialysis sessions a week. The Italian Society of Nephrology should promote trials and the National Health Service should provide funds for these promising hemodialysis schedules.

Activator protein 2alpha mediates parathyroid TGF-alpha self-induction in secondary hyperparathyroidism

In secondary hyperparathyroidism, enhanced expression of TGF-alpha in the parathyroid leads to its own upregulation, generating a feed-forward loop for TGF-alpha activation of its receptor, EGFR receptor (EGFR), which promotes parathyroid hyperplasia. These studies examined the role of activator protein 2alpha (AP2), an inducer of TGF-alpha gene transcription, in the upregulation of parathyroid TGF-alpha in secondary hyperparathyroidism. In rat and human secondary hyperparathyroidism, parathyroid AP2 expression strongly correlated with TGF-alpha levels and with the rate of parathyroid growth, as expected. Furthermore, the increases in rat parathyroid content of AP2 and its binding to a consensus AP2 DNA sequence preceded the increase in TGF-alpha induced by high dietary phosphate. More significant, in A431 cells, which provide a model of enhanced TGF-alpha and TGF-alpha self-induction, mutating the core AP2 site of the human TGF-alpha promoter markedly impaired promoter activity induced by endogenous or exogenous TGF-alpha. Important for therapy, in five-sixths nephrectomized rats fed high-phosphate diets, inhibition of parathyroid TGF-alpha self-induction using erlotinib, a highly specific inhibitor of TGF-alpha/EGFR-driven signals, reduced AP2 expression dosage dependently. This suggests that the increases in parathyroid AP2 occur downstream of EGFR activation by TGF-alpha and are required for TGF-alpha self-induction. Indeed, in A431 cells, erlotinib inhibition of TGF-alpha self-induction caused parallel reductions in AP2 expression and nuclear localization, as well as TGF-alpha mRNA and protein levels. In summary, increased AP2 expression and transcriptional activity at the TGF-alpha promoter determine the severity of the hyperplasia driven by parathyroid TGF-alpha self-upregulation in secondary hyperparathyroidism.

Does vitamin D receptor and calcium receptor activation therapy play a role in the histopathologic alterations of parathyroid glands in refractory uremic hyperparathyroidism?

BACKGROUND AND OBJECTIVES

Vitamin D receptor activation by vitamin D sterols and calcium-sensing receptor stimulation by cinacalcet are the most powerful treatments of secondary hyperparathyroidism. This study was aimed to assess a possible association between histopathologic changes of parathyroid tissue and treatment modality.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Studies were performed on 82 parathyroids of 22 adult white hemodialysis patients undergoing first parathyroidectomy. The type of hyperplasia and the distribution of chief and oxyphil cells, expressed as oxyphil/chief cell ratio, were assessed. Three groups could be studied according to treatment modality: group A consisted of 6 patients who were treated with cinacalcet, intravenous calcitriol, and phosphate binders; group B consisted of 6 patients who were treated with intravenous calcitriol and phosphate binders, and group C consisted of 10 patients who were treated with phosphate binders alone.

RESULTS

Sixty-eight (82.9%) out of 82 glands removed showed nodular hyperplasia. It was more frequent in groups A and B than in group C. A stepwise forward logistic regression model showed that the probability of nodular hyperplasia was higher in patients who were on calcitriol and/or cinacalcet therapy, in female gender and in patients with a higher body mass index. Oxyphil/chief cell ratio also was significantly different among the three groups. Cinacalcet treatment was the only predictor of this ratio.

CONCLUSIONS

An association was found between calcitriol and/or cinacalcet therapy and a high prevalence of nodular hyperplasia, and between cinacalcet therapy and high oxyphil/chief cell ratio. The meaning of the observed associations remains uncertain.

[Occlusion of hemodialysis vascular accesses by means of endovascular procedures]

Correct management of complications is crucial to the long-term survival of vascular access for hemodialysis. The present work report our experience with endovascular procedures in the occlusion of complicated arteriovenous fistulas (AVFs) and grafts in patients with a high surgical risk. Among the endovascular procedures carried out between January 2003 and December 2006, all those regarding the occlusion of vascular accesses by means of embolization or exclusion were selected retrospectively. Embolization means the release into the circulation of material to occlude the vascular lumen; exclusion is obtained by means of covered stents, which, when placed in a blood vessel, exclude its ramifications. Seven procedures of endovascular occlusion of vascular accesses were performed in the study period. All patients were considered as having a high surgical risk or presented technical difficulties related to surgical intervention. Venous hypertension was the indication in 5 cases and grade III or IV steal syndrome was the indication in 2 cases. Six AVFs were treated: 2 distal radiocephalic, 1 brachiocephalic, 2 brachiobasilic, and 1 Gracz AVF; an antebrachial graft was also treated. Occlusion was obtained in 4 cases by means of embolization and in 3 cases by means of exclusion. The technical success was 100% with virtually no complications. Endovascular occlusion of vascular access represents an effective and safe procedure in selected cases, also when compared with the surgical approach. Furthermore, the different technical solutions available allow to adequately solve the problems linked to anatomical variability and to the sites of the vascular accesses.

Development and Validation of Bioimpedance Analysis Prediction Equations for Dry Weight in Hemodialysis Patients

BACKGROUND

Accurate assessment of hydration status and specification of dry weight (DW) are major problems in the clinical treatment of hemodialysis (HD) patients. Bioelectrical impedance analysis (BIA) has been recognized as a noninvasive and simple technique for the determination of DW in HD patients.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

This study was designed to develop and validate BIA prediction equations for DW in HD patients. It included white adults (1540 disease-free adults with normal body mass index [BMI] and 456 prevalent and 27 incident HD patients). All participants underwent at least one single-frequency BIA measurement (800 muA and 50 kHz alternating sinusoidal current with a standard tetrapolar technique). The BIA variable measured was resistance (R). Data of 1463 (95% of the cohort) disease-free individuals with normal BMI (prediction sample) were used to establish best-fitting BIA prediction equations of body weight. The latter were cross-validated in the residual 5% subset (77 individuals) of the same cohort (validation sample).

RESULTS

Multiple regression analysis showed a significant relationship among body weight, R, age, and height in 739 men (R(2) = 0.82, P < 0.0001) and among body weight, R, and height in 724 women (R(2) = 0.68, P < 0.0001) in the prediction sample. The Bland Altman analysis showed a mean difference between predicted and measured body weight of 0.3 +/- 1.0 kg (95% confidence interval +/- 2.0 kg) in the validation sample. The BIA prediction equations that were obtained in disease-free individuals with normal BMI were applied to a cohort of 456 prevalent HD patients: The mean difference between achieved and estimated DW was 0.1 +/- 1.0 kg (P = 0.53) in men and -0.3 +/- 1.0 (P = 0.76) in women. Finally, BIA prediction equations were tested in a cohort of 27 incident HD patients. The mean difference between predicted and achieved DW was -0.6 +/- 1.0 kg (P = 0.76) in men and 0.6 +/- 1.0 (P = 0.50) in women.

CONCLUSIONS

This study was able to develop and validate BIA prediction equations for DW in HD patients. They seem to be a promising tool; however, they still need external validation.

Cinacalcet is effective in relapses of secondary hyperparathyroidism after parathyroidectomy

BACKGROUND

Relapses of secondary hyperparathyroidism (SHPTH) after parathyroidectomy (PTx) in haemodialysis patients are relatively frequent. Calcimimetics (cinacalcet HCl) offer a new therapeutic opportunity for their treatment. However, no data about the treatment with cinacalcet of relapses of SHPTH after PTx are available in literature. The aim of this single-centre prospective study was to evaluate the therapeutic efficacy of cinacalcet in this high-risk category of patients.

METHODS

Twelve haemodialysis patients of our Dialysis Unit had a relapse of SHPTH after PTx, defined as serum levels of immunoreactive intact parathyroid hormone (iPTH)>300 pg/ml. They were stratified into a treatment group (the six patients having the highest serum levels of iPTH) and a control group (the remaining six patients): the former were treated for 6 months with a dose of cinacalcet ranging from 30 mg every other day to 60 mg a day; the latter continued to be administered the conventional treatment. Serum levels of albumin, iPTH, calcium (Ca), phosphate (P) and alkaline phosphatase were determined monthly. The treatment group included four cases of nodular hyperplasia and two cases of carcinoma of parathyroid glands, whereas the control group included four cases of nodular hyperplasia and two cases of diffuse hyperplasia.

RESULTS

At the start of the study, the six patients treated with cinacalcet showed a more severe picture of biochemical abnormalities when compared with the control patients. After 6 months of treatment, a statistically significant reduction in the serum levels of iPTH, Ca, P and CaxP product was obtained only in the patients treated with cinacalcet. Symptomatic episodes of hypocalcaemia (serum Ca<7.0 mg/dl) were observed in three patients of this group. The six patients undergoing the conventional treatment showed at 6 months a not significant decrease in the mean serum levels of iPTH and a not significant increase in the mean serum levels of Ca, P and CaxP product, when compared with the baseline values.

CONCLUSIONS

Our single-centre prospective study, even though small and of short duration, shows that cinacalcet is effective also in controlling relapses of SHPTH after PTx, thus representing a solid, and sometimes unique, therapeutic opportunity for this high-risk category of patients.

[Management of arteriovenous fistula: anastomosis and more....]

The huge amount of human and economic resources necessary for a vascular access creation in haemodialysis strongly requires a very careful patient assessment and the choice of the most appropriate procedures, both aiming at improving quality of care and optimizing available resources. This review focuses on arteriovenous fistula (AVF) monitoring and surveillance, not only by following current guidelines, but also by exploring the most interesting data of the literature; attention is particularly focused on the haemodynamic aspects of AVF, which play a relevant role not only in himself. the natural history of vascular access, but also of the patient.

Sestamibi Scintigraphy, Topography, and Histopathology of Parathyroid Glands in Secondary Hyperparathyroidism

BACKGROUND

Several imaging techniques presently are available to assess the location of hyperplastic parathyroid glands. The purpose of the present study is to assess the place of dual-phase technetium Tc 99m-sestamibi (MIBI) scintigraphy in the preoperative localization of hyperplastic parathyroid glands in patients with severe secondary hyperparathyroidism (SHPT).

METHODS

We studied 35 consecutive adult white hemodialysis patients undergoing a first parathyroidectomy after performing MIBI scintigraphy. Hyperplasia of the parathyroid glands was classified as diffuse (DH) or nodular (NH). Statistical analysis was conducted by comparing patients with MIBI-negative (no focal area of increased uptake) with MIBI-positive (> or = 1 focal area of increased uptake) results and stratifying parathyroid glands according to location (superior and inferior).

RESULTS

MIBI scintigraphy showed focal areas of increased uptake in at least 1 gland in 25 patients (71.4%). Total number of focal areas of increased uptake was 42 of 121 glands removed (sensitivity, 34.7%; specificity, 100%). One hundred one glands showed NH and 20 glands showed DH. The 25 patients with MIBI-positive results had 85 pathological glands removed, and the 10 patients with MIBI-negative results had 36 pathological glands removed: in the former, most glands showed NH (77 of 85 glands; 90.6%), and in the latter, 24 of 36 glands showed NH (66.7%; P = 0.004 at chi-square test). The sensitivity of MIBI scintigraphy for distinguishing specific subtypes of hyperplasia was 37.6% (38 of 101 glands) for NH and 20.0% (4 of 20 glands) for DH (P = 0.0005). The following values were significantly greater in inferior compared with superior glands: (1) estimated weight (2.1 +/- 0.8 versus 1.6 +/- 1.2 g; P = 0.04), (2) percentage of MIBI positivity (34 of 42 inferior glands [80.9%] versus 8 of 42 superior glands [19.1%]; P = 0.0001), and (3) percentage of localization permitted by MIBI scintigraphy (34 of 63 inferior glands [54.0%] versus 8 of 58 superior glands [13.8%]; P = 0.0001). Thus, NH, although equally distributed between inferior (53 of 63 glands) and superior (48 of 58 glands) glands, showed a percentage of MIBI positivity significantly greater in inferior (34 of 53 glands [64.1%]) compared with superior glands (8 of 48 glands [16.7%]; P = 0.0001).

CONCLUSION

MIBI scintigraphy did not show high sensitivity in identifying hyperplastic glands, although it was able to identify those with NH better than those with DH. Thus, MIBI scintigraphy has limited value preoperatively for patients with SHPT. Estimated weight, percentage of MIBI positivity, and percentage of localization permitted by MIBI scintigraphy were significantly greater in inferior glands.