Ranking of factors determining potassium mass balance in bicarbonate haemodialysis.

BACKGROUND: One of the most important pathogenetic factors involved in the onset of intradialysis arrhytmias is the alteration in electrolyte concentration, particularly potassium (K(+)). METHODS: Two studies were performed: Study A was designed to investigate above all the isolated effect of the factor time t on intradialysis K(+) mass balance (K(+)MB): 11 stable prevalent Caucasian anuric patients underwent one standard (∼4 h) and one long-hour (∼8 h) bicarbonate haemodialysis (HD) session. The latter were pair-matched as far as the dialysate and blood volume processed (90 L) and volume of ultrafiltration are concerned. Study B was designed to identify and rank the other factors determining intradialysis K(+)MB: 63 stable prevalent Caucasian anuric patients underwent one 4-h standard bicarbonate HD session. Dialysate K(+) concentration was 2.0 mmol/L in both studies. Blood samples were obtained from the inlet blood tubing immediately before the onset of dialysis and at t60, t120, t180 min and at end of the 4- and 8-h sessions for the measurement of plasma K(+), blood bicarbonates and blood pH. Additional blood samples were obtained at t360 min for the 8 h sessions. Direct dialysate quantification was utilized for K(+)MBs. Direct potentiometry with an ion-selective electrode was used for K(+) measurements. RESULTS: Study A: mean K(+)MBs were significantly higher in the 8-h sessions (4 h: -88.4 ± 23.2 SD mmol versus 8 h: -101.9 ± 32.2 mmol; P = 0.02). Bivariate linear regression analyses showed that only mean plasma K(+), area under the curve (AUC) of the hourly inlet dialyser diffusion concentration gradient of K(+) (hcgAUCK(+)) and AUC of blood bicarbonates and mean blood bicarbonates were significantly related to K(+)MB in both 4- and 8-h sessions. A multiple linear regression output with K(+)MB as dependent variable showed that only mean plasma K(+), hcgAUCK(+) and duration of HD sessions per se remained statistically significant. Study B: mean K(+)MBs were -86.7 ± 22.6 mmol. Bivariate linear regression analyses showed that only mean plasma K(+), hcgAUCK(+) and mean blood bicarbonates were significantly related to K(+)MB. Again, only mean plasma K(+) and hcgAUCK(+) predicted K(+)MB at the multiple linear regression analysis. CONCLUSIONS: Our studies enabled to establish the ranking of factors determining intradialysis K(+)MB: plasma K(+) → dialysate K(+) gradient is the main determinant; acid-base balance plays a much less important role. The duration of HD session per se is an independent determinant of K(+)MB.

Efficacy and Safety of a New Technique of Conversion from Temporary to Tunneled Central Venous Catheters.

The usually applied conversion technique from temporary to tunneled central venous catheters (CVCs) using the same venous insertion site requires a peel-away sheath. We propose a conversion technique without peel-away sheath: a guide wire is advanced through the existing temporary CVC; then, a subcutaneous tunnel is created from the exit to the venotomy site. After removing the temporary CVC, the tunneled one is advanced along the guide wire. The study group included all patients requiring a catheter conversion from January 2012 to June 2014; the control group included incident patients who had received de novo placement of tunneled CVCs from January 2010 to December 2011. The main outcome measures were technical success and immediate complications. Seventy-two tunneled catheters (40 with our conversion technique and 32 with the traditional one) were placed in 72 patients. The technical success was 95% in the study group and 75% in the controls (p = 0.019). The immediate complications were one bleeding in the study group (2.5%) and one air embolism, one pneumothorax, and four bleedings (18.7%) in the controls (p = 0.039). Conversion from temporary to tunneled CVC using a guide wire and without a peel-away sheath is an effective and safe procedure.

Rethinking an effective AV fistula-graft screening program. An "A B C".

The goal of a vascular access screening program is to detect and preemptively correct hemodynamically significant stenosis, however, a practice pattern allowing to implement such a program still remains to be defined. Achieving balance between the increase in access-related procedures by adopting an aggressive screening program, and the risks associated with the absence of any screening program, i.e., failure or abandonment of the arterio-venous access with need for central venous catheter placement, can be extremely challenging. All major guidelines agree about the role of arterio-venous access monitoring, but the way surveillance should be managed is still a controversial issue. Preserving long-term vascular access function should be a goal for all hemodialysis teams, yet it ideally requires a multidisciplinary effort with a monitoring program, calling for a great deal of involvement by hemodialysis health professionals. In this context, the engagement of skilled nurses and the role of patient empowerment with collaborative decision-making may be the key to a successful vascular access screening program. Screening programs should be personalized, shared with the patients, and tailored according to vascular access type and site. In the near future, new devices and the use of artificial intelligence may allow to support interpretation of complex data and lead to the development of prediction models for vascular access failure.

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.

Optimizing the dialysate calcium concentration in bicarbonate haemodialysis.

BACKGROUND: There is no consensus regarding the optimal dialysate calcium concentration (DCa) during haemodialysis (HD). Low DCa may predispose to acute arrhythmias, whereas high DCa increases the long-term risk of soft tissue calcifications. METHODS: Twenty-two HD patients treated in four dialysis centres underwent two HD sessions, respectively, with 1.5 and 1.25 mmol/L total DCa. Calcium mass balance (CMB) was calculated from ionized calcium (iCa) in the dialysate and blood at the start and end of each run, using a kinetic formula to define the mean concentrations in the blood and dialysate and then estimating CMBs over the entire treatments. RESULTS: Mean blood iCa levels increased using 1.5 DCa, whereas they remained unchanged using 1.25 DCa. Diffusive CMB positively correlated with the dialysate/blood iCa gradient. With 1.5 DCa, diffusive CMBs were strongly positive at the blood side and negative at the dialysate side, indicating transfer from dialysate to blood. With 1.25 DCa, despite a negative dialysate/blood iCa gradient, diffusive CMB was slightly positive in blood and negative in dialysate. The global balances based on both the convective and diffusive components showed a positive net transfer of Ca from dialysate to blood with 1.5 DCa and an approximately neutral Ca flux with 1.25 DCa. CONCLUSIONS: While CMB is nearly neutral when using 1.25 DCa, the use of 1.5 DCa results in a gain of Ca during HD. The risks associated with Ca load should be considered in the choice of DCa prescription for HD but need also be weighed against the risk of worse haemodynamic dialysis tolerance.

Haemodynamic stability in standard bicarbonate haemodialysis and long-hour slow-flow bicarbonate haemodialysis.

BACKGROUND: The interplay of correct solute mass balances, such as that of sodium (Na+) and potassium (K+) (respectively, Na+MB and K+MB) with adequate ultrafiltration volumes (V(UF)), is crucial in order to achieve haemodynamic stability during haemodialysis (HD). The GENIUS single-pass batch dialysis system (Fresenius Medical Care, Germany) consists of a closed dialysate tank of 90 L; it offers the unique opportunity of effecting mass balances of any solute in a very precise way. METHODS: The present study has a crossover design: 11 stable anuric HD patients underwent two bicarbonate HD sessions, one of 4 h and the other of 8 h in a random sequence, always at the same interdialytic interval, at least 1 week apart. The GENIUS system and high-flux FX80 dialysers (Fresenius Medical Care, Germany) were used. The volume of blood and dialysate processed, V(UF) and dialysate Na+ and K+ concentrations were prescribed to be the same. Plasma water Na+ and K+ trends during dialysis as well as Na+MBs and K+MBs were determined. At the same time, systolic blood pressure (SBP) and diastolic blood pressure (DBP), mean arterial pressure (MAP) and heart rate trends during dialysis were analysed. Plasma volume (PV) changes were computed from plasma total protein concentrations and their trends analysed. RESULTS: Plasma water Na+ and K+ levels were not significantly different when comparing the start and the end of the sessions of the two treatments. Both the increase of plasma water Na+ levels and the decrease of plasma water K+ levels in the first 4 h were significantly slower during the 8-h sessions when compared with the 4-h ones (P < 0.048 and P < 0.006, respectively). Dialysis sessions were uneventful. SBP decreased significantly during the 4-h sessions, whereas it remained stable during the 8-h ones (P < 0.0001 and P = NS, respectively). Statistically significantly lower intradialysis decreases of SBP (-4.5 ± 16.2 vs -20.0 ± 15.0 mmHg, P < 0.02) and MAP (-1.4 ± 11.7 vs -8.6 ± 11.0 mmHg, P < 0.04) were achieved in the 8-h sessions with respect to the 4-h sessions, in spite of no significant difference for mean V(UF) (2.9 ± 0.9 vs 2.9 ± 0.8 L; P = NS) and mean Na+MBs (-298.1 ± 142.2 vs -286.2 ± 150.7 mmol; P = NS). The decrease of PV levels in the first 4 h was significantly slower during the 8-h sessions when compared with the 4-h ones (P < 0.0001). PV decrease was significantly higher at the end of the 4-h HD sessions than at the end of the 8-h HD sessions (P < 0.043). CONCLUSIONS: The present highly controlled experiments using a crossover design and precise Na+MB and K+MB controls showed that better haemodynamic stability was achieved in the 8-h sessions with respect to the 4-h sessions, in spite of no difference for mean V(UF) and Na+MBs. Thus, other pathophysiological mechanisms, namely, a better PV preservation, must be advocated in order to explain the better haemodynamic stability peculiar to long-hour slow-flow nocturnal HD treatments.

Removal of uraemic retention solutes in standard bicarbonate haemodialysis and long-hour slow-flow bicarbonate haemodialysis.

BACKGROUND: Several studies already stressed the importance of haemodialysis (HD) time in the removal of uraemic toxins. In those studies, however, also the amount of dialysate and/or processed blood was altered. The present study aimed to investigate the isolated effect of the factor time t (by processing the same total blood and dialysate volume in two different time schedules) on the removal and kinetic behaviour of some small, middle and protein-bound molecules. METHODS: The present study had a crossover design: 11 stable anuric HD patients underwent two bicarbonate HD sessions (~ 4 and ~ 8 h) in a random sequence, at least 1 week apart. The GENIUS single-pass batch dialysis system and the high-flux FX80 dialysers (Fresenius Medical Care, Bad Homburg, Germany) were used. The volume of blood and dialysate processed, volume of ultrafiltration, and dialysate composition were prescribed to be the same. For each patient, blood was sampled from the arterial line at 0, 60, 120, 180 and 240 min (all sessions), and at 360 and 480 min (8-h sessions). Dialysate was sampled at the end of HD from the dialysate tank. The following solutes were investigated: (i) small molecules: urea, creatinine, phosphorus and uric acid; (ii) middle molecule: ß(2)M; and (iii) protein-bound molecules: homocysteine, hippuric acid, indole-3-acetic acid and indoxyl sulphate. Total solute removals (solute concentration in the spent dialysate of each analyte × 90 L - the volume of dialysate) (TSR), clearances (TSR of a solute/area under the plasma water concentration time curve of the solute) (K), total cleared volumes (K × dialysis time) (TCV), and dialyser extraction ratios (K/blood flow rate) (ER) were determined. The percent differences of TSR, K, TCV and ER between 4- and 8-h dialyses were calculated. Single-pool Kt/Vurea, and post-dialysis percent rebounds of urea, creatinine and ß(2)M were computed. RESULTS: TSR, TCV and ER were statistically significantly larger during prolonged HD for all small and middle molecules (at least, P < 0.01). Specifically, the percent increases of TSR (8 h vs 4 h) were: for urea 22.6.0% (P < 0.003), for creatinine 24.8% (P < 0.002), for phosphorus 26.6% (P < 0.001), and for ß(2)M 39.2% (P < 0.005). No statistically significant difference was observed for protein-bound solutes in any of the parameters being studied. Single-pool Kt/Vurea was 1.41 ± 0.19 for the 4-h dialysis sessions and 1.80 ± 0.29 for the 8-h ones. The difference was statistically significant (P < 0.0001). Post-dialysis percent rebounds of urea, creatinine and ß(2)M were statistically significantly greater in the 4-h dialysis sessions (at least, P < 0.0002). CONCLUSIONS: The present controlled study using a crossover design indicates that small and middle molecules are removed more adequately from the deeper compartments when performing a prolonged HD, even if blood and dialysate volumes are kept constant. Hence, factor time t is very important for these retention solutes. The kinetic behaviour of protein-bound solutes is completely different from that of small and middle molecules, mainly because of the strength of their protein binding.

Is there a link between the late occurrence of a brachial artery aneurysm and the ligation of an arteriovenous fistula?

Arteriomegaly and aneurysms proximal to long-standing posttraumatic arteriovenous fistulas (AVF) have been described. Much fewer are the reports of the late occurrence of brachial artery aneurysms following the closure of a hemodialysis AVF. Here, we report the case of a 55-year-old male patient. He had received a cadaver donor kidney transplant in 1996; his distal radiocephalic (RC) wrist AVF in the left arm had been ligated in 2001; he developed an aneurysm of the left brachial artery 9 years after the ligation of the AVF (2009). He underwent the surgical intervention of aneurysmectomy at the level of the left brachial artery with construction of a bypass with autologous saphenous vein. In conclusion, the development of a RC wrist AVF is an intrinsically dynamic process characterized by the increase in both blood flow rate and internal diameter of the brachial artery; the latter might be associated with enhanced fracture of the elastic fibers with the consequent risk of the development of an aneurysm. Thus, arteriomegaly and aneurysm of the brachial artery proximal to long-standing AVFs might be seen as a "continuum" of these morphologic modifications.

How to manage catheter-related right atrial thrombosis: Our conservative approach.

BACKGROUND: Catheter-related right atrial thrombosis is an underestimated, severe, and life-threatening complication of any type of central venous catheters. No clear-cut epidemiological data are available. Catheter-related right atrial thrombosis is often asymptomatic; however, it can lead to serious complications and death. CASE SERIES: We report seven catheter-related right atrial thrombosis events occurred in five hemodialysis patients; two recurrences following primary treatment are included in the report, all of them managed with a conservative approach without catheter removal. Systemic anticoagulation (vitamin K antagonists), having a well-defined target of International Normalized Ratio of 2.5-3.0, combined with urokinase as a locking solution at the end of each hemodialysis session were the therapeutic strategy used in all patients. After the first month, the anticoagulation target was reduced to an International Normalized Ratio value of 1.5-2.0 and urokinase to a weekly administration. After sixth months, when no thrombus was identified at transthoracic echocardiographic examinations, the treatment was stopped. No bleeding complications were reported. CONCLUSION: The combination therapy here described is safe, quick, and effective, achieving the goal of not removing catheters.

Comparison of alternative methods for scaling dialysis dose.

BACKGROUND: Kt/Vurea was established as an index of haemodialysis (HD) adequacy. The use of Vurea 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, liver size (LV) and more recently, bioelectrical resistance (R), an independent and directly measurable biological parameter, were proposed as alternative methods for scaling dialysis dose. METHODS: The present study aimed to prospectively evaluate the predictive power of some demographic, anthropometric, bioelectrical (BIA) and biochemical parameters, of seven scaling parameters, namely Vurea, as derived from the Watson et al. formulae, W(0.67), BSA, REE, HMRO, LV and R and of eight HD adequacy indices [single-pool variable-volume Kt/Vurea, computed using the Daugirdas equation, its rescaled equivalents (Kt/W(0.67), Kt/BSA, Kt/REE, Kt/HMRO, Kt/LV and Kt/R) and Kt] on long-term survival of a cohort of 328 incident white HD patients. All individuals underwent periodical (every 3 months) biochemical evaluations and single-frequency BIA measurements, injecting 800 microA at 50 kHz alternating sinusoidal current with a standard tetrapolar technique. RESULTS: A first Cox regression analysis, testing the predictive power of some demographic, anthropometric, BIA and biochemical parameters, and of the eight HD adequacy indices on long-term survival of the patients, showed that only higher serum creatinine (Scr) levels (P < 0.0001) and lower Kt/R values (P < 0.04) were significant outcome predictors. As Kt was shown not to be an outcome predictor, a second Cox regression analysis, testing the predictive power of the same demographic, anthropometric, BIA and biochemical parameters, and of the seven scaling parameters on long-term survival of the patients, was built. It showed that only higher Scr levels (P < 0.0001) and higher R values (P < 0.04) were significant outcome predictors. Kaplan-Meier survival analyses of the patients stratified into two groups, respectively, according to the first quartile of R values (0.0-467.8 Ohm), the fourth quartile of Kt/R values (98-106 ml/Ohm) and the first quartile of Scr levels (0.0-11.6 mg/dl) showed a significantly higher long-term survival in the groups of patients having R values above the first quartile (P < 0.04), Kt/R values below the fourth quartile (P < 0.03) and Scr levels above the first quartile (P < 0.0001). CONCLUSIONS: Kt/R, R and Scr were independent significant predictors of long-term-survival in incident HD patients: R is related to the fluid status, whereas Scr, which reflects the lean body mass, seems to suggest that body composition is more important than body weight and/or body mass index. Further work is required to develop these concepts and to translate them into rigorous outcome-based adequacy targets suitable for clinical usage.

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.

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.

[A case of drug-induced syndrome of inappropriate secretion of antidiuretic hormone]. / Un caso di sindrome da inappropriata secrezione di ormone antidiuretico indotta da farmaci.

The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is characterized by hyponatremia, plasma hypo-osmolality, a urine sodium concentration >30-40 mmol/L, normal acid-base balance, a normal plasma potassium concentration and, frequently, hypouricemia. There are different types of SIADH: idiopathic, iatrogenic, and forms caused by central nervous system or lung disorders, neoplasia and major surgical interventions. Drug-induced SIADH is becoming the most frequent cause of hyponatremia encountered in clinical practice. Here we report the case of a 60-year-old man in a coma (I-II) and with very severe hyponatremia (99 mmol/L) due to SIADH induced by fluphenazine and amitriptyline, which he had been taking since many years as antidepressant drugs. SIADH became very quickly more severe due to the recent administration of cisplatin. There was rapid improvement of the clinical symptoms after withdrawal of the drugs involved and correction of hyponatremia. In conclusion, in rare cases like the present one hyponatremia related to SIADH may be so severe as to represent a true clinical emergency. The administration of drugs known to cause hyponatremia should be avoided, if possible; otherwise, very careful monitoring of the plasma sodium concentration is mandatory to avoid severe neurological complications which may lead to the death of the patient.

[Uremic toxins: the case of protein-bound compounds]. / Tossine uremiche: il caso dei "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.

Autogenous side-to-side brachial-basilic fistulas without vein transposition: a valuable option?

An autogenous brachial-basilic arteriovenous fistula (BBAVF) in the upper arm must be considered before placing prosthetic grafts in hemodialysis patients with multiple failures of forearm AVFs. The aim of this observational study was to compare technical and clinical outcomes of a new construction technique for BBAVF (n-BBAVF) with that of the standard one-stage side-artery to end-vein transposed BBAVF (t-BBAVF). A n-BBAVF is constructed in the following way: basilic vein and brachial artery are isolated. Patency of the proximal and distal vein is verified by injecting warmed (37 degrees C) saline solution. A venotomy and an arterotomy of 4-5 mm are performed. The two vessels are prepared for a side-to-side anastomosis without transposition of the vein. The latter allows both an antegrade and retrograde flow along the basilic vein, both proximally and distally to the anastomosis with more sites available for the venipunctures of the dialysis. Thirty BBAVFs were constructed as the secondary or tertiary vascular access in 30 patients over a 4-year period: 17 patients with adequate forearm basilic vein underwent the construction of a n-BBAVF; 13 underwent the construction of a t-BBAVF. The construction of a n-BBAVF requires a significantly lesser surgical time (55.0 +/- 9.0 minutes vs. 115.0 +/- 18.0, p < 0.0001), has fewer surgical complications (5.9% vs. 46.2%, p < 0.0001), and a reduced time to first use (24.5 +/- 6.3 vs. 37.7 +/- 9.1 days, p < 0.0001) than that of a t-BBAVF. n-BBAVFs showed a relatively low rate of thrombosis per patient-year at risk (0.067 at 1 year and 0.099 at 2 years). The latter was significantly lower at 1 year when compared with t-BBAVFs (0.067 vs. 0.285; p < 0.004). Our policy of "all AVFs should be autogenous" led us to the construction of a vascular access which is based on a side-to-side anastomosis between the brachial artery and the basilic vein without transposition of the vein allowing both antegrade and retrograde flow into the basilic vein. The results of this surgical technique appear satisfactory.

Is the removal of a central venous catheter always necessary in the context of catheter-related right atrial thrombosis?

Catheter-related right atrial thrombosis is a severe and life-threatening complication of central venous catheters in both adult and young patients. Catheter-related right atrial thrombosis can occur with any type of central venous catheters, utilized either for hemodialysis or infusion. Up to 30% of patients with central venous catheter are estimated to be affected by catheter-related right atrial thrombosis; however, neither precise epidemiological data nor guidelines regarding medical or surgical treatment are available. This complication seems to be closely associated with positioning of the catheter tip in the atrium, whereas it is unlikely with a tip located within superior vena cava. Herein, we report the case of a patient affected by catheter-related right atrial thrombosis, who showed a quick resolution of thrombosis with a new therapeutic scheme combining loco-regional thrombolytic therapy (urokinase as a locking solution) and systemic anticoagulation therapy (vitamin K antagonists), thus avoiding catheter removal. Neither complications of the combination therapy were reported, nor recurrence of catheter-related right atrial thrombosis occurred. In conclusion, the combination therapy here described was safe, quick and effective, achieving the goal of not removing the catheter.

[Membranoproliferative glomerulonephritis with relapsing episodes of acute kidney injury in the Schnitzler syndrome].

The Schnitzler syndrome (SS) is a rare and underdiagnosed entity that associates a chronic urticarial rash, monoclonal IgM (or sometimes IgG) gammopathy and signs and symptoms of systemic inflammation. During the past 45 years the SS has evolved from an elusive, little-known disorder to the paradigm of a late-onset auto-inflammatory acquired syndrome. Though there is no definite proof of its precise pathogenesis, it should be considered as an acquired disease involving abnormal stimulation of the innate immune system, which can be reversed by the interleukin 1 (IL-1) receptor antagonist anakinra. Here we describe the case of a 56-year-old male Caucasian patient affected by SS and hospitalized several times in our unit because of relapsing episodes of acute kidney injury. He underwent an ultrasound-guided percutaneous kidney biopsy in September 2012, which showed the histologic picture of type I membranoproliferative glomerulonephritis. He has undergone conventional therapies, including nonsteroidal anti-inflammatory drugs, steroids and immunosuppressive drugs; more recently, the IL-1 receptor antagonist anakinra has been prescribed, with striking clinical improvement. Although the literature regarding kidney involvement in the SS is lacking, it can however be so severe, as in the case reported here, to lead us to recommend the systematic search of nephropathy markers in the SS.

Kidney involvement in the Schnitzler syndrome, a rare disease.

The Schnitzler syndrome (SS) is a rare and underdiagnosed entity that associates a chronic urticarial rash, monoclonal IgM (or sometimes IgG) gammopathy and signs and symptoms of systemic inflammation. During the past 45 years, the SS has evolved from an elusive little-known disorder to the paradigm of a late-onset acquired auto-inflammatory syndrome. Though there is no definite proof of its precise pathogenesis, it should be considered as an acquired disease involving abnormal stimulation of the innate immune system, which can be reversed by the interleukin-1 receptor antagonist anakinra. It clearly expands our view of this group of rare genetic diseases and makes the concept of auto-inflammation relevant in polygenic acquired diseases as well. Increasing numbers of dermatologists, rheumatologists, allergologists, haematologists and, more recently, nephrologists, recognize the SS. The aim of this review is to focus on kidney involvement in the SS. Although the literature regarding kidney involvement in the SS is very poor it can be severe, as in our own case here reported, leading us to recommend the systematic search for nephropathy markers in the SS.

The impact of haemodialysis arteriovenous fistula on haemodynamic parameters of the cardiovascular system.

BACKGROUND: Satisfactory vascular access flow (Qa) of an arteriovenous fistula (AVF) is necessary for haemodialysis (HD) adequacy. The aim of the present study was to further our understanding of haemodynamic modifications of the cardiovascular system of HD patients associated with an AVF. The main objective was to calculate using real data in what way an AVF influences the load of the left ventricle (LLV). METHODS: All HD patients treated in our dialysis unit and bearing an AVF were enrolled into the present observational cross-sectional study. Fifty-six patients bore a lower arm AVF and 30 an upper arm AVF. Qa and cardiac output (CO) were measured by means of the ultrasound dilution Transonic Hemodialysis Monitor HD02. Mean arterial pressure (MAP) was calculated; total peripheral vascular resistance (TPVR) was calculated as MAP/CO; resistance of AVF (AR) and systemic vascular resistance (SVR) are connected in parallel and were respectively calculated as AR = MAP/Qa and SVR = MAP/(CO - Qa). LLV was calculated on the principle of a simple physical model: LLV (watt) = TPVR·CO(2). The latter was computationally divided into the part spent to run Qa through the AVF (LLVAVF) and that part ensuring the flow (CO - Qa) through the vascular system. The data from the 86 AVFs were analysed by categorizing them into lower and upper arm AVFs. RESULTS: Mean Qa, CO, MAP, TPVR, LLV and LLVAVF of the 86 AVFs were, respectively, 1.3 (0.6 SD) L/min, 6.3 (1.3) L/min, 92.7 (13.9) mmHg, 14.9 (3.9) mmHg·min/L, 1.3 (0.6) watt and 19.7 (3.1)% of LLV. A statistically significant increase of Qa, CO, LLV and LLVAVF and a statistically significant decrease of TPVR, AR and SVR of upper arm AVFs compared with lower arm AVFs was shown. A third-order polynomial regression model best fitted the relationship between Qa and LLV for the entire cohort (R (2) = 0.546; P < 0.0001) and for both lower (R (2) = 0.181; P < 0.01) and upper arm AVFs (R (2) = 0.663; P < 0.0001). LLVAVF calculated as % of LLV rose with increasing Qa according to a quadratic polynomial regression model, but only in lower arm AVFs. On the contrary, no statistically significant relationship was found between the two parameters in upper arm AVFs, even if mean LLVAVF was statistically significantly higher in upper arm AVFs (P < 0.0001). CONCLUSIONS: Our observational cross-sectional study describes statistically significant haemodynamic modifications of the CV system associated to an AVF. Moreover, a quadratic polynomial regression model best fits the relationship between LLVAVF and Qa, but only in lower arm AVFs.