The risks associated with percutaneous native kidney biopsies: a prospective study

BACKGROUND

The known risks and benefits of native kidney biopsies are mainly based on the findings of retrospective studies. The aim of this multicentre prospective study was to evaluate the safety of percutaneous renal biopsies and quantify biopsy-related complication rates in Italy.

METHODS

The study examined the results of native kidney biopsies performed in 54 Italian nephrology centres between 2012 and 2020. The primary outcome was the rate of major complications 1 day after the procedure, or for longer if it was necessary to evaluate the evolution of a complication. Centre and patient risk predictors were analysed using multivariate logistic regression.

RESULTS

Analysis of 5304 biopsies of patients with a median age of 53.2 years revealed 400 major complication events in 273 patients (5.1%): the most frequent was a ≥2 g/dL decrease in haemoglobin levels (2.2%), followed by macrohaematuria (1.2%), blood transfusion (1.1%), gross haematoma (0.9%), artero-venous fistula (0.7%), invasive intervention (0.5%), pain (0.5%), symptomatic hypotension (0.3%), a rapid increase in serum creatinine levels (0.1%) and death (0.02%). The risk factors for major complications were higher plasma creatinine levels [odds ratio (OR) 1.12 for each mg/dL increase, 95% confidence interval (95% CI) 1.08-1.17], liver disease (OR 2.27, 95% CI 1.21-4.25) and a higher number of needle passes (OR for each pass 1.22, 95% CI 1.07-1.39), whereas higher proteinuria levels (OR for each g/day increase 0.95, 95% CI 0.92-0.99) were protective.

CONCLUSIONS

This is the first multicentre prospective study showing that percutaneous native kidney biopsies are associated with a 5% risk of a major post-biopsy complication. Predictors of increased risk include higher plasma creatinine levels, liver disease and a higher number of needle passes.

MO817: New Scenarios in Use of Calcimimetics: Could Etelcalcetide Improve Anaemia?

BACKGROUND AND AIMS

Alterations of mineral metabolism in patients with chronic renal failure (MBD-CKD) are frequently found and appear in the earliest stages of the disease. If not accurately diagnosed and treated, they could lead to serious clinical complications. With the same safety and better tolerability compared with cinacalcet, etelcalcetide demonstrated greater efficacy in the control of parathyroid hormone (iPTH) with an improvement in patients' compliance.

Several reports in the literature document the effect of elevated levels of iPTH on anaemia. In vitro experiments showed that elevated concentrations of PTH (comparable to those found in the blood of uraemic patients with secondary hyperparathyroidism) exert a significant inhibition on erythroid progenitors, decreasing the number of erythropoietin receptors on erythroid progenitors and making these cells insensitive to erythropoietin.

High levels of iPTH could have, furthermore, a haemolytic effect on the peripheral RBCs causing disturbed calcium metabolism, increased cytosolic calcium and enhanced osmotic fragility of the cells.

Aim of this study was to verify in a dialysis cohort if etelcalcetide could not only improve iPTH levels but also haemoglobin levels with a reduction in weekly doses of erythropoiesis-stimulating agents (ESA).

METHOD

We analysed data from 130 haemodialysis adult patients over 2 years from three different centres. A total of 24 patients treated with etelcalcetide (Image 1) were enrolled and followed at different time points (1–3–6–12–24 months). Patients were on stable doses of ferric carboxymaltose, active vitamin D analogues, phosphorus binders, supplement of oral calcium and calcium concentration in dialysate (1.25–1.50 mmol/L).

RESULTS

Data analysed after 24 months of treatment with etelcalcetide (Image 2) demonstrated not only a drastic improvement in iPTH values (772.53 ± 452.6 pg/mL versus 308.7 ± 207 pg/mL–60.05%) but also a statistically significant improvement of haemoglobin values ( 10.35 ± 1.45 g/dL versus 11.57 ± 0.97 g/dL;  P < .05) in addition to a reduction in the weekly ESAs units required (193.39 ± 148 UI/kg/week versus 142.71 ± 118 UI/kg/week; P < .05). This effect was achieved by maintaining constant ferritin and TSAT levels and without substantial changes in iron carboxymaltose therapy. No side effects were recorded for the entire duration of the treatment.

CONCLUSIONS

Considering the well-known direct and indirect inhibition of parathyroid hormone on erythropoiesis, reduction of iPTH levels achieved with etelcalcetide could improve haemoglobin levels and reduce required weekly ESA units, with obvious clinical and economic advantages. Further studies, on large populations and over longer periods of time, are required.

MO581ASSOCIATION OF ETELCALCETIDE WITH ADYNAMIC BONE DISEASE IN DIABETIC PATIENTS : A MULTI-CENTRIC STUDY

Background and Aims

Several dialysis patients frequently suffer of different mineral and bone disorders (CKD-MBD) associated with secondary hyperparathyroidism (sHPT). Among CKD-MBD, adynamic bone disease (ABD) is an alteration characterized by reduced osteblasts and osteoclasts, no accumulation of osteoid and low bone turnover. The histologic pattern of ABD is generally associated to low levels of PTH.

Etelcalcetide is a novel second-generation calcimimetic given intravenously after each hemodialysis session that has a longer elimination half-life than cinacalcet. Plasmatic concentration remains stable from 24 h to 48 h after injection. One potential risk of calcimimetics, such as etelcalcetide, is the dramatic and sustained PTH lowering, which could lead to the induction of adynamic bone disease (ABD). ABD and elevated serum levels of advanced glycation end products (AGEs) often are found in patients with renal failure caused by diabetic nephropathy since AGEs are involved in the pathogenesis of ABD by inhibiting osteoblastic activity and by parathyroid hormone secretion in response to hypocalcemia. So, diabetic patients treated with etelcalcetide could be considered at increased risk of developing ABD.

Aim of our study was to verify the incidence of adynamic bone disease, (defined by low PTH levels) in prevalent diabetic and non-diabetic HD patient of three large community Hospital.

Method

Data were collected from 3 dialysis units with n = 130 patients on the charge for a period of 1 year from start of the calcimimetic. A total of 40 patients ( 23 male, 17 female) on etelcalcetide were enrolled (21 Diabetic, 19 non diabetic patients). Time points of assessment included 1-3-6-12 months. Patients were 18-years-old or older; they were on stable doses of active vitamin D analogs, phosphorus binders, a supplement of oral calcium, and calcium concentration in dialysate (1.25–1.50 mmol/L)

Results

Median age was 55,9 years and dialysis vintage was 4.6 year. 59,5% percent of patients switched from cinacalcet to etelcalcetide (90 days from last cinacalcet prescription); the remaining patients were calcimimetic naive. 40% of patients had a history of at least one cardiovascular event 61.5% had a starting etelcalcetide dose of 5 mg and the median weekly dose was 7.5 mg (range: 2.5-15 mg).

On Diabetic Group: mean PTHi, Ca2+ and P before calcimimetic start was respectively 844±479,30 pg /mL , 9,95±0,97 mg/dl , 5,02±0,99 mg/dl. In non diabetic patients: mean PTHi, Ca2+ and P before calcimimetic start was: 793,36±534,41 150 pg /mL, 9,33±0,70 mg/dl, 5,9±1,17 mg/dl

Conclusion

Results of our study show that after 1 year of etelcalcetide treatment, levels of PTHi are lower more in non-diabetic patients, ( M12: 473±340,08 vs 253,13 + 98,87 p:0.042) despite scientific evidence currently supporting hypothesis that osteoblastic activity is reduced by AGES and ABD risk is increased in diabetic nephropathy. Therefore, etelcalcetide could be used safely in diabetic patients and could even protect from the risk of development ABD. However, further studies are required to validate this hypothesis.

Results are shown in the following table:

P1555REVERSIBLE AKI AND HEART INVOLVEMENT RESULTING FROM AMANITA PROXIMA POISONING TREATED WITH HAEMODIALYSIS: A SINGLE-CENTER CASE SERIES

Background and Aims

Worldwide, amatoxin-containing mushrooms account for >95% of mushroom poisoning-related death. Recently, Amanita species not containing amatoxin, such as Amanita Proxima, have been implicated in poisonings resulting in acute kidney injury. Allenic norleucine has been isolated from these fungi and accounts for their nephrotoxicity. AKI is characterized by interstitial nephritis on renal biopsy and resolves over weeks. Here we report several case of AKI associated with cardiac involvement. We aimed to describe improvement of cardiac output and resolution of AKI after replacement dialysis treatment.

Method

From January 2013 to January 2020, eight consecutive patients with AKI from Amanita Proxima poisoning were enrolled in a large Italian community hospital. We collected clinical data including hepatic, cardiac and renal function parameters. In all the cases studied, in addition to renal failure, there were a worsening of cardiac function.

Results

We identified 8 patients suffering from Amanita Proxima intoxication, with a mean age of 57.8±24.5 years (62.5% were female). All patients presented preliminary gastrointestinal symptoms occurred within 24 hours from the mushroom intake and suddenly developed kidney injury and underwent replacement dialysis treatment using standard bicarbonate dialysis. At baseline, patients' mean eGFR was 7±2.3 mL/min/1.73m, with a mean BUN of 124±41 mg/dl, AST 52,6±42,5 IU/L, ALT 115,5±105,7 IU/L,. Cardiac involvement was also found in all cases, evidenced by ECG alteration (62,5%), an increase in myocardial necrosis enzymes (87,5%) and a reduction in the ejection fraction (50%) of about 15 percent. In 25% of cases, typical chest pain was also found. Mean troponin was 3,82±7,31 ng/ml, myoglobin 243,55±275,18 ng/ml CPK 187,6±42 IU/L and CK-MB of 13,72±14,96 IU/L. Kidney failure and cardiac impairment was successfully resolved in 87.5% of poisonings. At the end of treatment all renal and cardiac parameters significantly decreased (P<0.001): mean eGFR was 57±24 mL/min/1.73m, mean BUN was 69±12.7 mg/dl, AST 23,57±9,77 IU/l, ALT 25±10,64 IU/L. Mean troponin was 0,04±0,03 ng/ml, myoglobin 111,8±93,39 ng/ml, CPK 68,33± IU/L and CK-MB 0,66± 0,61 IU/L.

Only one patient died for intoxication-related complication. The mean number of dialysis treatments to achieve the resolution of renal failure was eight.

Conclusions

The cases reported suggest that Amanita proxima have a potential severe cardiac toxicity that request a precise cardiac evaluation. Early identification of intoxication and rapid start of dialysis therapy are crucial for the resolution of heart damage.

What volume to choose to assess online Kt/V?

INTRODUCTION

Urea distribution volume (V) can be assessed in different ways, among them the anthropometric Watson Volume (V_W). However, many studies have shown that V_W does not coincide with V and that the latter can be more accurately estimated with other methods. The present multicentre study was designed to answer the question: what V to choose to assess online Kt/V?

MATERIALS AND METHODS

Pre- and postdialysis blood urea nitrogen concentrations and the usual input data set for urea kinetic modelling were obtained for a single dialysis session in 201 Caucasian patients treated in 9 Italian dialysis units. Only dialysis machines measuring ionic dialysance (ID) were utilized. ID reflects very accurately the mean effective dialyser urea clearance (Kd). Six different V values were obtained: the first one was V_W; the second one was computed from the equation established by the HEMO Study to predict the single pool-adjusted modelled V from V_W (V_H) (Daugirdas JT et al. KI 64: 1108, 2003); the others were estimated kinetically as: 1. V_ID, in which ID is direct input in the in the double pool variable volume (dpVV) calculation by means of the Solute-solver software; 2. V_Kd, in which the estimated Kd is direct input in the dpVV calculation by means of the Solute-solver software; 3. V_KTV, in which V is calculated by means of the second generation Daugirdas equation; 4. V_SPEEDY, in which ID is direct input in the dpVV calculation by means of the SPEEDY software able to provide results quite similar to those provided by Solute-solver.

RESULTS

Mean± SD of the main data are reported: measured ID was 190.6 ± 29.6 mL/min, estimated Kd was 211.6 ± 29.0 mL/min. The relationship between paired data was poor (R² = 0.34) and their difference at the Bland-Altman plot was large (21 ± 27 mL/min). V_W was 35.3 ± 6.3 L, V_H 29.5 ± 5.5, V_{_}ID 28.99 ± 7.6 L, V_{_}SPEEDY 29.4 ± 7.6 L, V_KTV 29.7 ± 7.0 L. The mean ratio V_W/V_ID was 1.22, (i.e. V_W overestimated V_ID by about 22%). The mean ratio V_H/V_ID was 1.02 (i.e. V_H overestimated V_ID by only 2%). The relationship between paired data of V_ID and V_W was poor (R² = 0.48) and their mean difference at the Bland-Altman plot was very large (-  6.39 ± 5.59 L). The relationship between paired data of V_ID and V_H was poor (R² = 47) and their mean difference was small but with a large SD (- 0.59 ± 5.53 L). The relationship between paired data of V_ID and V_SPEEDY was excellent (R² = 0.993) and their mean difference at the Bland-Altman plot was very small (- 0.54 ± 0.64 L). The relationship between paired data of V_ID and V_KTV was excellent (R² = 0.985) and their mean difference at the Bland-Altman plot was small (- 0.85 ± 1.06 L).

CONCLUSIONS

V_ID can be considered the reference method to estimate the modelled V and then the first choice to assess Kt/V. V_SPEEDY is a valuable alternative to V_ID. V_KTV can be utilized in the daily practice, taking also into account its simple way of calculation. V_W is not advisable because it leads to underestimation of Kt/V by about 20%.

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.

Pregnancy in end-stage renal disease patients on dialysis: how to achieve a successful delivery

Pregnancy in women with chronic kidney disease has always been considered as a challenging event both for the mother and the fetus. Over the years, several improvements have been achieved in the outcome of pregnant chronic renal patients with increasing rates of successful deliveries. To date, evidence suggests that the stage of renal failure is the main predictive factor of worsening residual kidney function and complications in pregnant women. Moreover, the possibility of success of the pregnancy depends on adequate depurative and pharmacological strategies in patients with end-stage renal disease. In this paper, we propose a review of the current literature about this topic presenting our experience as well.

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.

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.

The Mediterranean diet: a matter of history, tradition, culture and health

We can state that unhealthy diets are among the top 10 causes of mortality in Western countries. The Mediterranean diet is gaining popularity because it encourages weight loss, improving the quality of life by offering a variety of healthy and palatable foods. Moreover, it ensures adequate intake of fruits, vegetables, nuts, fish, fibers, legumes, cereals and olive oil, which have been associated with a longer lifespan of people thanks to their anti-inflammatory and antioxidant properties. Thus the Mediterranean diet could act as therapy in inflammatory diseases including cardiovascular disease, obesity, type 2 diabetes, metabolic syndrome and chronic renal failure.

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.

Omega-3 polyunsaturated fatty acids and proxies of cardiovascular disease in hemodialysis: a prospective cohort study

BACKGROUND

Omega-3 polyunsaturated fatty acids (omega-3 PUFAs) have antithrombotic, lipid-lowering and antiinflammatory properties. The aim of this study was to verify if dietary supplementation with omega-3 PUFAs is able to induce changes of blood pressure, nutritional and coagulative profile, inflammation and blood cell counts in patients on hemodialysis (HD).

METHODS

We designed a 12-month, prospective, single-blind, sequential intervention, cohort study. All of the HD patients undergoing HD in our unit were eligible for the study. Patients on HD for at least 6 months with an autologous vascular access were enrolled. No thresholds for blood pressure or lab parameters were considered. Patients taking nonsteroidal antiinflammatory drugs, steroids or statins or those with catheters, grafts, liver diseases, malignancies, malnutrition or sepsis were excluded. After the baseline evaluations the patients underwent 3 consecutive 4-month study periods taking the following supplements: A (olive oil: 2 g/day), B (omega-3 PUFA: 2 g/day), C (olive oil: 2 g/day).

RESULTS

Twenty-four patients met the inclusion criteria. All patients completed the follow-up. Fibrinogen, hemoglobin, platelet, red and white blood cell counts, parathormone (PTH), partial thromboplastin time (PTT), serum total cholesterol, triglycerides, apolipoprotein A and B, C-reactive protein (CRP) and albumin levels did not change significantly during the study. On the contrary, systolic (mean +/- SD) (A: 131 +/- 17.8 mm Hg; B: 122 +/- 12.8 mm Hg; C: 129 +/- 13.2 mm Hg), diastolic (A: 83 +/- 16.3 mm Hg; B: 72 +/- 14.8 mm Hg; C: 79 +/- 6.5 mm Hg) and mean blood pressure (A: 99 +/- 16.8 mm Hg; B: 88 +/- 14.1 mm Hg; C: 96 +/- 8.7 mm Hg) were significantly lower at the end of study period B (repeated measures ANOVA and Tukey's post hoc test: p<0.05).

CONCLUSIONS

In our experience, blood pressure was the only parameter influenced by omega-3 PUFA supplementation in patients on long-term HD.

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.

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.

Post-parathyroidectomy serum phosphate kinetics is peculiar to female hemodialysis patients with a high body mass index

BACKGROUND

Persistent hyperphosphatemia is one of the most important factors in the development of secondary hyperparathyroidism (sHPTH). Recently, we demonstrated that a higher body mass index (BMI) and female gender could predispose to a larger phosphate (P) body burden, thereby influencing the severity of sHPTH.

METHODS

This prospective study aimed to verify if these two risk factors, i.e. BMI and female gender, also influenced calcium (Ca) and P kinetics in the immediate post-parathyroidectomy (PTx) period in 42 consecutive adult Caucasian anuric hemodialysis (HD) patients referred for first PTx. Serum Ca and P were measured pre-PTx and on the 5 consecutive post-PTx days; serum immunoreactive parathyroid hormone (iPTH) and alkaline phosphatase (ALP) levels were measured pre-PTx and 3 days post-PTx.

RESULTS

Ablation of parathyroid tissue determined a significant reduction in serum iPTH, ALP, Ca and P (p = 0.001). The stratification of the cohort into four groups according to the cut-off value of BMI = 25 kg/m(2) and according to gender showed the following: males and females with BMI >25 kg/m(2) (analyzed both separately and as a subgroup including males and females) had significantly higher pre-PTx serum P levels, when compared with the respective sub-groups with BMI <25 kg/m(2) (p < 0.01); a significantly higher mean area under the concentration curve (AUC) of serum P was observed in the high BMI group (males and females), when compared with the low/normal BMI group (p = 0.03); the serum P kinetics in the 5 post-PTx days did not differ between the two groups of male patients (low/normal BMI males vs. high BMI males), whereas a significantly higher mean serum P AUC was observed in the high BMI female patients, when compared with the low/normal BMI female patients (p = 0.003); finally, the serum P kinetics in the 5 post-PTx days did not differ between the two groups of low/normal male and female patients, whereas a significantly higher mean serum P AUC was observed in the high BMI female patients, when compared with the high BMI male patients (p = 0.006). A linear multiple regression analysis with the serum P AUC of each patient as a dependent variable and BMI, gender, age and dialysis duration as independent variables showed that BMI (p = 0.0001) and female gender (p = 0.001) were independent predictors of the serum P AUC.

CONCLUSIONS

High BMI and female gender are associated with peculiar serum P kinetics in the immediate post-PTx period, suggesting the existence of a larger P body burden in high BMI female HD patients. The existence of a larger P pool exclusively based on serum P kinetics prompts the need for further studies to better understand such intriguing aspects of bone pathophysiology in response to parathyroid gland removal in chronically uremic patients.

A high body mass index and female gender are associated with an increased risk of nodular hyperplasia of parathyroid glands in chronic uraemia

BACKGROUND

A persistent hyperphosphataemia represents one of the most important factors in the development of secondary hyperparathyroidism (sHPTH). The present prospective study was designed in order to test the hypothesis that a higher body mass index (BMI) may predispose to a larger body burden of phosphate (P), influencing by that way the severity of sHPTH.

METHODS

Histological studies were performed on 168 parathyroid glands of 42 consecutive adult Caucasian haemodialysis patients (20 males and 22 females) referred for first parathyroidectomy (PTx): each parathyroid gland was graded as 0, when only or mainly diffuse hyperplasia was found, or as 1, when only or mainly nodular hyperplasia was found. Thus, parathyroid histology was scored on a 5-point scale: 0 = diffuse hyperplasia in the four glands; 1 = nodular hyperplasia in one gland; 2 = nodular hyperplasia in two glands; 3 = nodular hyperplasia in three glands; 4 = nodular hyperplasia in the four glands. For sake of simplicity, the three less severe histological gradings, i.e. scores 0-2 were grouped together and indicated as score group 2.

RESULTS

The distribution of the patients was the following: 28.6% were in the score group 2, 23.8% in the score group 3 and 47.6% in the score group 4 (20 patients, 14 of whom were females). The output of the one-way ANOVA with the histological scores as grouping variable and age, dialysis duration, BMI and pre-PTx serum iPTH, alkaline phosphatase (ALP), calcium (Ca) and P as predictors showed that only BMI was different among the three histological scores (P = 0.001). By stratifying the analysis by gender, the relationship between BMI and histological scores was confirmed only in females (P = 0.006). The stratification of the entire cohort into two groups according to the cut-off value of BMI = 25 kg/m(2) showed that: (i) score 4 was more prevalent in the high-BMI group and score 2 in the normal-BMI group (P = 0.01); (ii) female gender was more represented in the high-BMI group (12 out of 18 patients, P = 0.04); and (iii) the pre-PTx serum P levels were significantly higher in the high-BMI group (P = 0.008). The output of the linear multiple regression analysis with pre-PTx serum P as dependent variable and BMI, pre-PTx serum ALP and Ca as independent variables (selected according to the statistical significance in the bivariate correlations) showed that only serum Ca and BMI were statistically significant predictors of serum P levels.

CONCLUSIONS

A high BMI and female gender are associated with an increased risk of nodular hyperplasia of parathyroid glands in adult Caucasian haemodialysis patients. The two risk factors, above all if combined in the same patient, appear to predispose to a larger body burden of P, increasing by that way the severity of sHPTH.

Comorbid conditions and gender impact the primary survival of distal radio-cephalic arteriovenous fistula inpatients on long-term hemodialysis

BACKGROUND

Vascular access failure complicates the clinical picture of patients on long-term hemodialysis, increasing the number of hospitalizations and the respective costs. In these patients we analyzed the possible meaningful relationship between comorbidities and primary survival of the autologous distal radio-cephalic arteriovenous fistula (dAVF), pointing out the influence of other variables on that relationship.

METHODS

We evaluated the dAVF placed in our unit between January 1, 1995, and December 31, 2003, on 105 patients (55 males) 63.8 +/- 14.1 (average +/- SD) years old. The dAVF creation date was the starting point while the dAVF failures due to either thrombosis or malfunction (KT/V < 1.2) were the study end-point. Death, conversion to peritoneal dialysis, transfer to other units and renal transplantation were assumed as censure criteria. ICED score, single comorbidities, use of temporary catheter at the hemodialysis initiation, serum lipids and CRP levels, hematocrit, blood platelet count and coagulative parameters (at the time of the dAVF creation) were considered as covariates. The Kaplan-Meier method and Cox's proportional hazards regression were used in the dAVF survival analysis.

RESULTS

During the study we recorded 38 dAVF failures (median primary survival of the dAVF 487.3 days, with a failure rate of 0.645 per patient-year). Age, lab variables, single comorbidities, and use of temporary catheters did not impact the dAVF primary survival. Conversely ICED score > 1 (P = 0.014; hazard ratio = 1.648; 95% CI = 1.106-2.454) as well as feminine gender (P = 0.018; hazard ratio = 1.640; 95% CI = 1.024-2.256) increased the risk of dAVF failure.

CONCLUSIONS

In our cohort of patients on long-term hemodialysis neither the single comorbidities nor the temporary catheterization influence the lifespan of the vascular access. However our data demonstrated the meaningful inverse relationship between dAVF primary survival and a composite comorbidity index reflecting not only the type of the diseases but also their associations and severities. This relationship was not influenced by other covariates although the feminine gender was significantly associated with worse survival of the vascular access.

Are low plasma levels of 25-(OH)vitamin D a major risk factor for hyperparathyroidism independent of calcitriol in renal transplant patients?

BACKGROUND

Recently, some studies have emphasized the role of plasma 25-(OH)vitamin D (25OHD) levels in mineral metabolism dysregulation in chronic kidney diseases (CKDs). However, to date little attention has been paid to 25OHD metabolism abnormalities after renal transplantation (Tx). This cross-sectional study aimed to focus on its role in mineral metabolism dysregulation in functioning Tx.

METHODS

Twenty-eight out of 75 Caucasian Tx patients were selected following strict inclusion and exclusion criteria. Two blood samples were effected at the end of the winter for the measurements of plasma 25OHD and calcitriol levels. Serum creatinine (Cr), alkaline phosphatase (SAP), immunoreactive intact parathyroid hormone (PTH), electrolytes and 24-hr proteinuria were also determined. The Kolmogorov-Smirnov test was used to evaluate the data distribution: serum Cr, Cr clearance, dialysis duration and PTH levels were non-normally distributed and were log-transformed. Values of p<=0.01 were assumed as statistically significant.

RESULTS

Median serum Cr and PTH levels were, respectively, 1.0 mg/dL and 90.0 pg/mL (range 27-420; normal range 10-65); most of our Tx patients (78.5%) had serum PTH levels above the upper limit of normal values. Mean plasma 25OHD concentration was 19.6 +/- 8.9 SD ng/mL (range: 6-36). None had levels <5 ng/mL (severe deficiency); 10 patients (35.7%) had mild deficiency (5-15 ng/mL); 14 patients (50%) had vitamin D insufficiency (16-30 ng/mL); and only four patients (14.3%) had target levels (>30 ng/mL). Mean plasma calcitriol levels were 69.7 +/- 19.0 pg/mL (range 47-105; normal range 35-85). They were not significantly correlated to plasma 25OHD levels. Proteinuria (292.6 +/- 147.0 mg/24 hr) inversely correlated to plasma 25OHD levels (r=-0.480; p<0.01). The bivariate correlation analysis between logPTH and the other parameters showed a significant correlation for SAP (r=0.494; p=0.008), plasma 25OHD levels (r=-0.442; p=0.01), proteinuria (r=0.452; p=0.01), log serum Cr (r=0.551; p=0.002) and log Cr clearance (r=-0.534; p=0.003). The other parameters did not correlate significantly with logPTH, notably plasma calcitriol and serum phosphate levels. Only the parameters significantly correlated to logPTH in the bivariate correlation analysis were included in the back stepwise multiple linear regression analysis as independent variables (model: p<0.0001; R2=0.54): among them, only plasma 25OHD levels (Beta=-0.486; p=0.001) and log serum Cr levels (Beta=0.589; p=0.0002) were the dependent variable logPTH predictors.

CONCLUSIONS

This cross-sectional study demonstrated that plasma calcitriol levels in a highly selected group of Tx patients were normal and not significantly correlated to either plasma 25OHD or serum PTH levels. Most patients (85.7%) had plasma 25OHD levels below the target value of 30 ng/mL; the latter were inversely correlated with serum PTH levels. Therefore, our study strengthens the suggestion that low plasma 25OHD levels are a major risk factor for secondary hyperparathyroidism (sHPTH) in Tx patients and stresses the importance of monitoring these patients.

[Cystatin C, beta2-microglobulin and C-reactive protein in hemodiafiltration and on-line endogenous liquid reinfusion and in low flux polysulphone bicarbonate conventional hemodialysis]

PURPOSE

Dialysis morbidity results partly from middle and large molecule retention, which is poorly removed by conventional hemodialysis (HD). The potential benefit of convective treatments could be the enhanced toxin removal over a wide molecular weight spectrum. This study aimed to evaluate cystatin C (cis), beta2-microglobulin (beta2-m) and C-reactive protein (CRP) removal behavior during hemodiafiltration reinfusion vs conventional low-flux HD (1.8 m2 low-flux polysulphone) (bicarbonate dialysis (BD)). The molecular weights of the substances evaluated in this study were as follows: cis = 13,300 daltons, beta2-m = 11,818 daltons, CRP = 160,000 daltons.

METHODS

Twelve patients on stable HD (six males, six females), were enrolled; six patients underwent BD and six patients underwent HFR. We measured arteriovenous serum cis, beta2-m and CRP levels, in three consecutive mid-week sessions at the following periods: pre/post-dialysis and after 60 min from the beginning of the session. At 60, 120 and 180 min of HFR, we collected the ultrafiltrate for cis, beta2-m, and CRP evaluation.

RESULTS

Cis, beta2-m and CRP mean values did not differ at pre-dialysis in the two groups. Pre/post- dialysis difference for cis in HFR vs BD was statistically significant (p=0.002) because cis reduced in HFR and increased in BD during the session. Beta2-m and CRP pre/post- dialysis differences in HFR vs BD were not significant. Cis clearance, measured 60 min after the beginning of the session was 34.2 +/- 20.1 mL/min in HFR and 24.8 +/- 18.4 mL/min in BD (p<0.05). beta2-m and CRP clearances did not differ among the treatments. Regarding the ultrafitrate concentrations during the HFR session, cis significantly decreased (2.5 +/- 0.6 mg/dL at 60 min and 2.0 +/- 0.4 mg/dL at 180 min; p=0.004), as well as beta2-m (21.5 +/- 12.9 mg/dL and 19.0 +/- 14.1 mg/dL, respectively; p=0.02). Ultrafiltrate CRP values, as expected, did not differ during HFR.

CONCLUSIONS

This study demonstrated that cis, a middle molecule, is well depurated in HFR, while in BD it increases. Beta2-m, although better removed in the convective phase during HFR, does not demonstrate a removal difference in HFR and in BD. CRP, a large molecule, does not have significant removal. Since cis and beta2-m have almost the same molecular weight, why do they have a different depuration? We need further studies to evaluate if membranes can remove these molecules or if protein electrical charges or their stereoscopy enables their removal.

Does atorvastatin influence serum C-reactive protein levels in patients on long-term hemodialysis?

BACKGROUND

The increase in serum C-reactive protein (CRP) levels is an independent determinant of cardiovascular events in long-term hemodialysis (HD) patients. Recently, statins have shown anti-inflammatory properties in addition to their lipid-lowering effect.

METHODS

We designed a 6-month, prospective, randomized, controlled study to assess the safety and efficacy of atorvastatin in reducing serum CRP levels in long-term HD patients. Patients on HD therapy for at least 6 months, with autologous vascular access, were included. Patients presenting with illnesses and/or use of drugs that may affect CRP levels were excluded. After randomization, group A included 16 patients treated with atorvastatin (10 mg/d orally), and group B included 17 patients treated with placebo. Body mass index, Kt/V, normalized protein catabolic rate, mean blood pressure, and levels of hemoglobin, serum CRP, albumin, creatinine, lipids, and enzymes were recorded at baseline and after 6 months.

RESULTS

Qualitative/quantitative parameters were homogeneous between the groups at baseline. In group A, median serum CRP levels decreased from 9 mg/L (range, 5 to 22 mg/L) at baseline to 5 mg/L (range, 3 to 16 mg/L) after 6 months (P = 0.004). In group B, values were 8 mg/L (range, 4 to 14 mg/L) at baseline and 7 mg/L (range, 3 to 17 mg/L) after 6 months (P = 0.98). Serum CRP levels were lower in group A than group B at month-4 (5 mg/L; range, 3 to 11 mg/L versus 7 mg/L; range, 3 to 10 mg/L, respectively; P = 0.054) and month-6 evaluations (5 mg/L; range, 3 to 16 mg/L versus 7 mg/L; range, 3 to 17 mg/L, respectively; P = 0.060). After 6 months, only in group A was there a significant decrease in serum cholesterol levels (P = 0.041) and a significant increase in serum albumin levels (P = 0.004). Enzyme levels were stable during the study in both groups.

CONCLUSION

Administration of atorvastatin is safe in patients on long-term HD therapy and, in addition to its beneficial effects on lipid levels, induces a significant decrease in serum CRP levels, with a consequential increase in serum albumin levels.

The natural history of autogenous radio-cephalic wrist arteriovenous fistulas of haemodialysis patients: a prospective observational study

BACKGROUND

Clinical practice guidelines have supported vascular access surveillance programmes on the premise that the natural history of the vascular access will be altered by radiological or surgical interventions after vascular access dysfunction is detected. The primary objective of this study was to assess the actual risk of thrombosis of autogenous radio-cephalic (RC) wrist arteriovenous fistulas (AVFs) without any pre-emptive interventions.

METHODS

We enrolled 52 randomly selected adult Caucasian prevalent haemodialysis (HD) patients, all with autogenous RC wrist AVFs, into this prospective, observational study aimed to follow the natural history of their AVFs for 4 years. The protocol prescribed avoiding any surgical or interventional radiological procedures until access failure (AVF thrombosis or a vascular access not assuring a single-pool Kt/V > or =1.2). The subjects underwent yearly assessments of vascular access blood flow rate by means of a saline ultrasound dilution method.

RESULTS

All failures of vascular access were due to AVF thrombosis; none were attributed to an inadequacy of the dialysis dose. AVF thrombosis occurred in nine cases; a rate of 0.043 AVF thrombosis per patient-year at risk. A receiver operating characteristic curve, evaluating the diagnostic accuracy of baseline vascular access blood flow rate values in predicting AVF failure, showed an under-the-curve area of 0.82+/-0.05 SD (P = 0.01). The value of vascular access blood flow rate, identified as a predictor of AVF failure, was <700 ml/min with an 88.9% sensitivity and 68.6% specificity. When subdividing the population of AVFs into two groups according to the baseline vascular access blood flow rates, two out of the nine thromboses occurred among the AVFs that had baseline blood flow rates >700 ml/min (n = 31), whereas seven occurred among the AVFs that had baseline blood flow rates <700 ml/min (n = 21). The 4 year cumulative actuarial survival was 74.36 and 20.80%, respectively (log-rank test, P = 0.04). The 24 AVFs that remained patent at the end of the 4 years maintained a median blood flow rate > or =900 ml/min at all time points studied. Worth noting is that, five of them (20.8%) remained patent throughout the study with a blood flow rate consistently < or =500 ml/min.

CONCLUSIONS

This study shows a very low rate of AVF thrombosis per patient-year at risk and a high actuarial survival of autogenous RC wrist AVFs, particularly of those having a blood flow rate >700 ml/min. Thus, a vascular access blood flow rate <700 ml/min appears to be a reliable cut-off point at which to start a closer monitoring of this parameter-which may lead to further investigations and possibly interventions relevant to the function of the AVFs.

A comparison of methods for the measurement of hemodialysis access recirculation

BACKGROUND

NKF K-DOQI clinical practice guidelines recommend a regular monitoring of vascular access (VA) through several methods, such as VA recirculation (AR). Assessment of AR is crucial to avoid inefficiency of hemodialysis (HD). A non-urea based method has been developed (ultrasound dilution Transonics Hemodialysis Monitor--USM) which is considered the gold standard together with the two needle revised slow-stop-flow BUN recirculation method (S/SF). Furthermore, some other indicator dilution techniques, utilizing the dilution of serum potassium (K), glucose, hematocrit (Hct) and hemoglobin (Hb) have been recently described.

METHODS

Aim of the study was to compare some of these tests with the gold standards (the USM and the revised S/SF methods). One hundred-five adult HD patients were selected to participate; all had autogenous radiocephalic wrist arteriovenous fistulas (AVF). Studies included the assessment of AR by means of: A. non-urea based methods: 1. at the start of HD a blood sample was obtained from the arterial needle at the time of needle insertion for the measurement of serum K, Hb and Hct (respectively K1, Hb1 and Hct1). The blood circuit was connected and the pumping of blood was started at 200 mL/min. After 18 seconds, blood samples were drawn from the arterial line sampling port (K2, Hb2, Hct2). At this time, if AR is present, part of the saline entering the blood stream will dilute K2, Hb2, Hct2.AR (%) is =100 x (1 - Hb2/Hb1) in the case of Hb; 2. during the first 30 min USM was performed in triplicate (the blood pump rate was set to 300 mL/min); B. a urea based method: the revised S/SF method was performed at 30 min.

RESULTS

AR was absent when measured by means of the USM; it was absent even when cannulating the patients with the two needles placed as close as possible. AR measured by means of the USM was significantly different from AR measured by means of the other methods (means +/- SD, one-way analysis of variance, p < 0.0001).

CONCLUSIONS

AR in autogenous radiocephalic wrist AVFs was zero when measured by means of the USM; the revised S/SF method and the tests employing the dilution of Hb, Hct and serum K can be considered a valuable alternative to the USM.

Predictors of serum creatinine in haemodialysis patients: a cross-sectional analysis

BACKGROUND

C-reactive protein (CRP) levels, an acute phase response index, predict cardiovascular outcome and are inversely related to visceral proteins, including albuminaemia in haemodialysis patients. Less definite is the relationship between inflammation and markers of somatic proteins such as serum creatinine in such patients. To explore these questions, a cross-sectional analysis of potential predictors of serum creatinine was performed.

METHODS

One hundred and seventy-nine prevalent haemodialysis patients as of June 2001 were included in the cohort. Midweek pre-dialysis blood samples were collected during the months of June, September through to December 2001 inclusive, and determinations of serum urea (urease method), creatinine (alkaline picrate method) and CRP levels by means of a high sensitivity immunonephelometric method were performed. Furthermore, pre- and post-dialysis body weights were recorded and 2 min post-dialysis serum urea levels were determined three times. They were utilized for the calculation of single pool Kt/V and of normalized protein catabolic rate (nPCR). Each of the data represents the mean of three determinations made every 3 months in the study period.

RESULTS

The analysis of multivariate linear regression was able to validate our model characterized by a dependent variable, serum creatinine and four independent variables (age, CRP, Kt/V and nPCR) (R(2)=0.60; F=24.10; P<0.00001; SE=1.94). Age (-0.08 mg/dl decrease in serum creatinine per 1-year increase in age), Kt/V (-0.25 mg/dl decrease in serum creatinine per 0.1 increase in Kt/V) and nPCR (0.10 mg/dl increase in serum creatinine per 0.1 g protein/kg/day increase in nPCR) were independently predictive of serum creatinine (P<0.00001). CRP and dialysis vintage did not predict serum creatinine. Stratifying the patients for the effects of CRP, only CRP values </=4 mg/l were directly predictive of serum creatinine (P<0.00001), whereas CRP values >4 mg/l were not. A further insight was given by the stratification of the patients for the effects of the interquartile ranges of CRP: it showed a progressive and statistically significant reduction of beta-coefficient inversely related to the increasing CRP values (P=0.003). Thus, the nature of the correlation between CRP and serum creatinine changes with increasing CRP values: from being a direct one, it shows a trend towards a transformation into an indirect one with beta=0 at a CRP value of approximately 9 mg/l. However, this indirect relationship does not reach statistical significance.

CONCLUSIONS

The present cross-sectional study suggests that the activation of acute phase response does not influence creatinine metabolism in haemodialysis patients; in contrast, age, Kt/V and nPCR predict serum creatinine levels. Larger prospective trials are needed to achieve a definitive answer about the relationship between somatic proteins, acute phase response activation and nutrition in dialysis patients.

Efficacy and safety of haemodialysis treatment with the Hemocontrol biofeedback system: a prospective medium-term study

BACKGROUND

Hypovolaemia has been implicated as a major causal factor of morbidity during haemodialysis (HD). A model biofeedback control system for intra-HD blood volume (BV) changes modelling has been developed (Hemocontrol), Hospal Italy) to prevent destabilizing hypovolaemia. It is based on an adaptive controller incorporated in a HD machine (Integra), Hospal Italy). The Hemocontrol biofeedback system (HBS) monitors BV contraction during HD with an optical device. HBS modulates BV contraction rates by adjusting the ultrafiltration rate (UFR) and the refilling rate by adjusting dialysate conductivity (DC) in order to obtain the desired pre-determined BV trajectories.

METHODS

Nineteen hypotension-prone uraemic patients (seven males, 12 females; mean age 64.5+/-3.0 SEM years; on maintenance HD for 80.5+/-13.2 months) volunteered for the present prospective study that compared the efficacy and safety of bicarbonate HD treatment equipped with HBS, as a whole, with the gold-standard bicarbonate treatment equipped with a constant UFR and DC (BD). The study included three phases: Medium-term studies started with one period of 6 months of BD and always had a follow-up period of HBS treatment ranging from 14 to 30 months (mean 24.0+/-1.6); short-term studies started in September 1999, when all patients went back to BD treatment for a wash-out period of 4 weeks and a short-term study period of a further 3 weeks (phase A). Afterwards, they once again started HBS treatment for a wash-out period of 4 weeks and a short-term study period of a further 3 weeks (phase B). Every patient underwent acute studies during a single HD run, once during phase A and once in phase B. Resistance (R) and reactance (Xc) measurements were obtained utilizing a single-frequency (50 kHz) tetrapolar bioimpedance analysis (BIA). Extracellular fluid volume (ECV) was calculated from R, Xc, and height and body weight measurements using the conventional BIA regression equations.

RESULTS

The overall occurrence of symptomatic hypotension and muscle cramps was significantly less in HBS treatment in both medium- and short-term studies. Self-evaluation of intra- and inter-HD symptoms (worst score=0, best score=10) revealed a statistically significant difference, as far as post-HD asthenia was concerned (6.2+/-0.2 in HBS treatment vs 4.3+/-0.1 in BD treatment, P<0.0001). No difference was observed between the two treatments when comparing pre- and post-HD lying blood pressure, heart rate, body weights and body weight changes in medium- and short-term studies. The residual BV%/ Delta ECV% ratio, expression of the vascular refilling, was significantly higher during HBS treatment in acute studies.

CONCLUSIONS

HBS treatment is effective in lowering hypovolaemia-associated morbidity compared with BD treatment; this could be related to a greater ECV stability. Furthermore, HBS is a safe treatment in the medium-term because these results are not achieved through potentially harmful changes in blood pressure, body weight, and serum sodium concentration.