Predictive role of duplex Doppler ultrasonography in the diagnosis of acute renal obstruction in patients with unilateral renal colic.

OBJECTIVE: The aim of our study was to assess the role of Doppler ultrasonography (DU) by resistive index (RI) and the difference of the RI (DeltaRI) in patients with acute unilateral renal obstruction. PATIENTS AND METHODS: We studied 36 consecutive patients (12 female, 24 male; mean age 45.6 +/- 8.4 years) with suspected renal colic by intravenous pyelography (IVP) and DU with determination of the RI and the Delta RI. A RI of >= 0.70 and a DeltaRI of >= 0.06 were considered suggestive of obstruction. IVP was considered as the "gold standard". RESULTS: In the studied population, RI was 0.664 +/- 0.060 in the affected kidney site of symptoms and 0.614 +/- 0.025 in the contralateral one, with an overall Delta RI of 0.049 +/- 0.062. At IVP, 14 patients resulted within normal range (Group A; 39%), 6 patients showed lithiasis without obstruction (Group B; 17%), 8 patients showed delayed excretion of the contrast medium (Group C; 22%), and 8 patients showed a functional exclusion of the kidney (Group D; 22%). One-way analysis of variance showed the IVP group significantly related to Delta RI with the highest values in Groups C (DeltaRI of 0.093 +/- 0.051; p<0.001) and D (DeltaRI of 0.116 +/-0.030; p<0.001) in comparison with Group A (DeltaRI of 0.001 +/-0.038) and Group B (DeltaRI of 0.015 +/-0.024). No differences were detected between Groups C and D (p=0.223) and between Groups A and B (p-0.472). DeltaRI measurement with DU permitted to predict the renal obstruction with a sensitivity of 93.8%, a specificity of 95.0% and an accuracy of 94.4%. CONCLUSIONS: Intrarenal Doppler ultrasonography represents a sensitive and highly specific test that can significantly contribute to the diagnosis of obstruction in patients with acute renal colic. It should be used as the first line imaging method in suspected acute renal colic, as well as for patients with renal insufficiency, pregnant women or for patients with adverse reactions to contrast media

Color Doppler ultrasonography percutaneous transluminal angioplasty of vascular access grafts.

Percutaneous transluminal angioplasty (PTA) is a possible treatment for stenosis. This study aimed to verify the impact of a vascular access (VA) surveillance protocol, based on the detection of functional changes and their correction by a new PTA method for VA performed under color Doppler ultrasonography (CDU) guidance. We divided the patients into two groups: group A, before May 1999 (retrospective study) without the surveillance protocol, and group B, from 1 May 1999 to January 2001 (prospective study) with the surveillance protocol. Access blood flow (Qa) was assessed every 4 weeks by ultrasound velocity dilution. In cases of a reduction of >or=35% from the baseline value, VA was examined using CDU: if a stenosis >50% was detected, angioplasty was performed. In cases of Qa reduction <35% we continued monitoring. By Coxs multivariate analyses, only the use of PTA with or without stenting reduced the relative risk of thrombosis by 64% during the follow-up (p=0.017 confidence intervals 88%-15%) in group B patients. Secondary patency was 80% for VA in which we performed PTA with or without stenting at 18 months, and 58% at 18 months in which we did not perform PTA. Our data show how PTA under CDU is useful to maintain and to improve graft patency. This PTA under CDU guidance allows patients to avoid surgical intervention, hospitalization, and adverse reactions to contrast media and exposure to ionizing radiation, with reduced cost and with better graft survival.

[Clinical relevance of study results]. / Rilevanza dei risultati di uno studio clinico.

The critical appraisal process of available evidence includes the evaluation of clinical importance of the study findings. This should coincide with the minimum worthwhile effect expected by the investigators in the study design and planning. In hard outcome studies it can be quantified by the absolute risk difference between groups and its reciprocal, known as number needed to treat to avoid one adverse event, or benefit (NNTB). The number needed to treat to produce harmful consequences of treatment (NNTH) should also be taken into account. Finally these effect measures, like risks and incidence proportions, are usually rough estimates of the true effects, due to non-complete follow-up of the observations under study. Underlying assumptions and design issues are especially important to assess the clinical relevance of any results.

[Water quality cuts down the chronic inflammatory risk: how to obtain it and keep it over time]. / La qualità dell'acqua abbatte il rischio infiammatorio cronico: come produrla e garantirla nel tempo.

BACKGROUND: Every week, approximately 400 liters of water used for dialysate production come into direct contact, through the semi-permeable membrane of the dialyzer, with the dialysis patient's blood stream. Therefore, submitting municipal water to an adequate depuration process before its use for dialysis becomes necessary. METHODS: Problems related to the implementation, updating and management of a dialysis water treatment system are analyzed. The results of the most recent multicenter studies on dialysis fluids quality are also reviewed. RESULTS: The best approach to plan, implement and manage a dialysis water treatment system, first, consists of defining the standards of chemical and microbiological water quality. The most diffused and commonly accepted standards are those recommended by the Association for Advancement of Medical Instrumentation (AAMI) and the European Pharmacopea (EP), which allow a maximum bacterial growth of, respectively, 200 CFU/ml and 100 CFU/mL and a maximum endotoxin concentration of 2 IU/mL and 0.25 IU/mL. A modern dialysis water treatment system provides a final purification process, mainly by reverse osmosis (RO), together with different pre-treatment levels and a hydraulic distribution circuit. Therefore, as RO produces water of optimal chemical and microbial quality, all efforts in the dialysis unit must be aimed at keeping this quality as constant as possible over time, by carrying out effective maintenance strategies and system disinfection. Nevertheless, several multicenter studies reported that 7-35% of water samples exceed a bacterial growth of 200 CFU/mL and that 44% of them display endotoxin concentrations >5 IU/mL. CONCLUSIONS: The results of multicenter studies indicate that the microbial quality of dialysis fluids is, unfortunately, still an often neglected problem. Evidence of a possible relationship between dialysis fluid contamination and patient morbidity, as well as the availability of systems and machines allowing purity levels that were unimaginable only a few years ago, must be a stimulus for modifying clinical practices and starting the improvement processes aimed at maximally reducing the risk of microbial contamination in the dialysis water, as already done with chemical contamination.

The role of underlying nephropathy in the progression of renal disease.

BACKGROUND: Disease-specific pathogenic mechanisms may be major determinants of the spontaneous rate of progression of chronic renal failure (CRF). To clarify the role of different underlying renal diseases, we examined the rate of CRF progression in 886 patients with chronic nephropathies. METHODS: Secondary analysis of two multicenter, prospective randomized trials: the Northern Italian Cooperative study (NIC) and the AIPRI study (ACE-Inhibition in Progressive Renal Insufficiency). Univariate and multivariate analyses of variance were used to select the covariates possibly related to CRF progression (estimated by means of the slope of the reciprocal of SCr against time), focusing on the contributory role of primary renal diseases. RESULTS: The overall rate of CRF progression was relatively low but there was a considerable difference in the slopes relating to the underlying nephropathy (particularly evident in the patients with chronic glomerulonephritis (CGN)). The median rate of CRF progression in both studies was more rapid in patients with polycystic kidney disease (PKD) and CGN than in those with other nephropathies. Multivariate analysis showed PKD as an independent predictor of the CRF progression rate only in the NIC Study (P < 0.0015); the selected variables in both studies predicted a variation of only 15-18% in the CRF progression rate. CONCLUSION: The underlying renal disease certainly plays a role in the natural history of CRF, but the variability of the CRF progression rates related to different renal diseases and between individuals with the same diagnosis underlines the need for caution in evaluating risk factors and predicting single patient outcomes.

Evaluation of dialysis outcomes: experimental versus observational evidence.

Evidence-based medicine provides tools to evaluate dialysis outcomes by integrating knowledge obtained from interventional and observational studies. This is illustrated in relation to three important topics: dialysis membranes, dialysis dose and anemia. Clinical trials and observational evidence support each other in indicating a decrease in dialysis-related amyloidosis morbidity when high-flux dialysis is used, whereas the impact of dialysis membranes on mortality is still controversial. Two clinical trials are currently investigating this issue: the American Hemodialysis (HEMO) Study and the European Membrane Permeability and ESRD Patient Outcome (MPO) Study. As indicated by the National Cooperative Dialysis Study (NCDS), dialysis dose is an important determinant of patient outcome. Although Gotch's analysis of the NCDS showed no further benefits for Kt/V>0.9, the analysis by Keshaviah showed a progressive benefit as Kt/V increased beyond 0.9. This finding has been confirmed by observational studies, of which the Dialysis Outcome and Practice Patterns Study (DOPPS) is the most recent and interesting. Further information is also expected from the HEMO study. The findings of observational and interventional studies are consistent in indicating anemia as a major determinant of morbidity and mortality in dialysis patients. American and European guidelines advise hemoglobin levels of 11-12 g/dl and hematocrit levels of 33-36%. The real benefit of completely correcting anemia is not so clear. In conclusion, far from being in opposition, clinical trials and observational studies can provide an integrated contribution to the analysis of dialysis outcomes.

Effect of sodium pool changes on blood pressure in patients undergoing PFD: design of a prospective randomized multicenter trial.

Blood pressure control is important during dialysis and the interdialytic period because of the frequency and potential seriousness of hypotension and hypertension. Water and sodium removal play an important role in the genesis of intradialytic cardiovascular instability or hypertension. Changing dialysate sodium concentrations without the aid of a kinetic model can sometimes give good results but is only an empirical approach. Therefore, this clinical trial was designed to prospectively investigate the advantages of changes in the sodium pool on the blood pressure profile of patients undergoing paired filtration dialysis (PFD). The hypothesis to be tested is whether using a dialysate conductivity which, according to the conductivity kinetic model, ensures that the conductivity of the ultrafiltrate at the end of each dialysis session is 0.3 mS/cm more (B) or less (C) than the mean during the run-in period, improves blood pressure control either in patients prone to intradialytic hypotension or patients who are hypertensive or normotensive with antihypertensive treatment. Patients will be randomly allocated to one of two treatment sequences (where treatment A is standard PFD): AABB or ABAA for patients with intradialytic hypotension; AACC or ACAA for hypertensive patients. During the experimental phase arterial blood pressure will be measured and symptoms reported by the patients will be recorded.

Combined treatment with steroids and azathioprine in IgA nephropathy: design of a prospective randomised multicentre trial.

Corticosteroids have had variable success in IgA nephropathy (IgAN). Our previous trial with a six-month course of steroids in IgAN patients showed they were effective in reducing the risk of renal function deterioration and proteinuria, but this effect seemed to decrease in the long term. This new randomised trial was designed to prospectively evaluate whether adding low-dose azathioprine to steroids improves long-term renal survival in adult biopsy-proven IgAN patients with proteinuria > or = 1 g/24 h and plasma creatinine < or = 2.0 mg/dl. The patients will be treated with steroids (methylprednisolone 1 g i.v. for three consecutive days at months 1, 3 and 5, plus oral prednisone 0.5 mg/kg every other day for six months) plus azathioprine 1.5 mg/kg/day for six months or steroids alone with the same schedule. Altogether a minimum of 346 patients should be enrolled within a four-year recruitment period. The planned duration of follow-up is five years.

Survival of prosthetic grafts of different materials after impairment of a native arteriovenous fistula in hemodialysis patients.

In our department, hemodialysis vascular accesses with graft, are used in patients with impairment of native distal and proximal arteriovenous fistulas (AVF-E). The aim of this study was to compare the survival of grafts of different materials (PTFE vs. bovine vein) in these patients. From 1991 to 1999, we prospectively evaluated 53 patients (35 women, 18 men, age 68 +/- 11 years, on dialysis for 70 +/- 65 months). Fifty-three PTFE, 10 reinforced PTFE, and 22 bovine vein grafts were placed. We evaluated the primary patency (PP) (days between fistula placement and the last dialysis before thrombosis occurred) and the secondary patency (SP) (days between fistula placement and the last dialysis treatment before it was considered lost) by separating PTFE survival from that of bovine veins. In the same patients, we also evaluated the survival of the native arteriovenous fistulas (AVF-E) during the pregraft period. Furthermore, we evaluated 404 patients (172 women, 232 men, age 65 +/- 14 years, on dialysis for 50 +/- 53 months) in whom only AVF-E were placed during the same follow-up period. Graft and AVF-E survival were calculated according to the Kaplan-Meier method. In patients with grafts, the PP at 1 year was 17.4% for PTFE and 23.9% for bovine veins. At 12 months, the SP of bovine veins was significantly higher than that of PTFE (81,9% vs. 50%, p < 0.04). In the patients who only had AVF-E, the PP and SP was, respectively, 43% at 12 months and 52.4% at 50 months. A preliminary experience in 22 patients with a 20 month follow-up confirms better survival of bovine veins than PTFE (p < 0.04).

Conductivity: on-line monitoring of dialysis adequacy.

Cardiovascular disease and the inadequacy of delivered dialysis are the main factors determining morbidity and mortality in dialysis patients. We have already demonstrated that a conductivity kinetic model makes it possible to match interdialytic sodium loading and intradialytic sodium removal (the main factor determining cardiovascular morbidity) without the need for blood samples and, thus, in routine clinical practice. The aim of the present study was to test the possibility of using the conductivity method also to determine Kt/v without blood or dialysate sampling. In 18 steady-state patients, the urea distribution volume (V) was kinetically determined once using ionic dialysance (D) values instead of those of effective urea clearance. One month later, the Kt/V was determined by using the current D and T values and the predetermined V (Dt/V), then compared with the equilibrated Kt/V computed by means of the SPVV kinetic model (eqKt/V). The mean value of Dt/V was 1.18+/-0.15; while of eqKt/V it was 1.18+/-0.16, with a mean difference of 0.00+/-0.07. The conductivity method therefore seems to be very promising not only for monitoring the sodium balance, but also for quantifying delivered dialysis. Since its simplicity and low-cost make it suitable for use at each dialysis session, the conductivity method could therefore lead to significant progress in dialytic practice by contributing to the elimination of the two main causes of morbidity and mortality in dialysis patients.

Monitoring sodium removal and delivered dialysis by conductivity.

As cardiovascular stability and the delivery of the prescribed dialysis "dose" seem to be the main factors in determining the morbidity and mortality of hemodialyzer patients today, it is of paramount importance to match hydro-sodium removal with interdialytic load and to verify the delivered dialysis at each session. A specially designed Biofeedback Module (BM--COT Hospal) allows the automatic determination of plasma water conductivity and effective ionic dialysance with no need for blood samples. Using BM, we evaluated the validity of "conductivity kinetic modelling" (CKM) and the possibility that this may substitute "sodium kinetic modelling". Moreover, we evaluated the "in vivo" relationship between ionic dialysance and effective urea clearance. Our results demonstrate that: 1) CKM makes it possible to obtain programmed end-dialysis plasma water conductivity with an error of less than +/- 0.14 mS/cm, roughly equivalent to a sodium concentration of +/- 1.4 mEq/L. 2). Ionic dialysance and effective urea clearance are not equivalent but, as the interrelationship between these is known, the BM allows the routine monitoring of delivered dialysis.

Echocardiography and right ventricular function in NKF stage III cronic kidney disease: Ultrasound nephrologists' role.

TAPSE measurement during echocardiography is a well known measure of right heart systo-diastolic function. Low TAPSE means reduced cranio-caudal excursion of tricuspidal annulus, sign of both reduced ejection fraction and reduced distensibility of right ventricle. It is a good prognostic index for cardiac mortality risk in CHF patients, adding significant prognostic information to NYHA stadiation. Nephrologists do not always fully aware of right ventricular function in their patients affected by chronic renal failure (CRF), even if this datum is probably crucial in vascular access policy. Our study was designed to study right ventricle function and TAPSE on 202 patients affected by moderate chronic renal failure, free from overt pulmonary hypertension. TAPSE, PAPs, right chambers diameters, classical Framingham factors, estimated glomerular filtration rate were recorded. TAPSE was reduced (<23 mm) in 43% of patients enrolled, while dilated right chambers were present in 24%. PAPs exceeded 30 mmHg in 29% of patients. Echocardiographic signs of left ventricular hypertrophy were found in 36% of patients. The ejection fraction was normal in all patients. Statistical analysis showed a significant indirect correlation between TAPSE and PAPs and between TAPSE and tele-diastolic diameters and volumes of the right ventricle, while a direct correlation was observed between TAPSE and Framingham score. TAPSE showed a bimodal distribution, with a subpopulation "low TAPSE - high PAPs", next to a population characterized by normal values ??for both parameters. A reduction in compliance and systolic function of the right heart chambers is quite early and frequent in course of CKD, a fact that the nephrologist should take in due consideration, managing blood volume or planning vascular access for hemodialysis.

Doppler ultrasound and renal artery stenosis: An overview.

Renovascular disease is a complex disorder, most commonly caused by fibromuscular dysplasia and atherosclerotic diseases. It can be found in one of three forms: asymptomatic renal artery stenosis (RAS), renovascular hypertension, and ischemic nephropathy. Particularly, the atherosclerotic form is a progressive disease that may lead to gradual and silent loss of renal function. Thus, early diagnosis of RAS is an important clinical objective since interventional therapy may improve or cure hypertension and preserve renal function. Screening for RAS is indicated in suspected renovascular hypertension or ischemic nephropathy, in order to identify patients in whom an endoluminal or surgical revascularization is advisable. Screening tests for RAS have improved considerably over the last decade. While captopril renography was widely used in the past, Doppler ultrasound (US) of the renal arteries (RAs), angio-CT, or magnetic resonance angiography (MRA) have replaced other modalities and they are now considered the screening tests of choice. An arteriogram is rarely needed for diagnostic purposes only. Color-Doppler US (CDUS) is a noninvasive, repeatable, relatively inexpensive diagnostic procedure which can accurately screen for renovascular diseases if performed by an expert. Moreover, the evaluation of the resistive index (RI) at Doppler US may be very useful in RAS affected patients for predicting the response to revascularization. However, when a discrepancy exists between clinical data and the results of Doppler US, additional tests are mandatory.

[P value and confidence intervals: reporting and interpreting the result of a clinical study]. / Guida al corretto uso della P e degli Intervalli di Confidenza nella lettura e presentazione dei risultati di uno studio clinico.

The main purpose of statistics in the analysis of clinical and epidemiological studies is to summarize data and information, as well as assess variability, trying to distinguish between chance findings and results that may be replicated upon repetition. Statistical analyses only convey the effect of chance element in data (random error). Statistics cannot control non-sampling errors concerning study design, conduct and methods adopted. At the end of the study, a result is defined statistically significant if the observed difference in the outcome variable is too large to be attributed to chance. A small P value provides evidence against the null hypothesis (of no effect), since data have been observed that would be unlikely if the null hypothesis was true. However, confidence intervals estimate separate the two data dimensions (strength of the relation between exposure and disease, and precision with which the relation is measured), and add to the hypothesis testing useful information for finding interpretation and further research.

Peritoneal transport assessment by peritoneal equilibration test with 3.86% glucose: a long-term prospective evaluation.

The peritoneal equilibration test (PET) with 3.86% glucose concentration (3.86%-PET) has been suggested to be more useful than the standard 2.27%-PET in peritoneal dialysis (PD), but no longitudinal data for 3.86%-PET are currently available. A total of 242 3.86%-PETs were performed in 95 incident PD patients, who underwent the first test during the first year of treatment and then once a year. The classical parameters of peritoneal transport, such as peritoneal ultrafiltration (UF), D/D(0), and D/P(Creat), were analyzed. In addition, the absolute dip of dialysate sodium concentration (DeltaD(Na)), as an expression of sodium sieving, was studied. D/D(0) was stable, and a progressive decrease in UF was observed after the second PET, whereas D/P(Creat) firstly increased and then stabilized. DeltaD(Na) was the only parameter showing a progressive decrease over time. On univariate analysis, D/D(0) and DeltaD(Na) were found to be significantly associated with the risk of developing UF failure (risk ratio (RR) 0.987 (0.973-0.999), P=0.04, and RR 0.768 (0.624-0.933), P=0.007, respectively), but on multivariate analysis only DeltaD(Na) showed an independent association with the risk of developing UF failure (RR 0.797 (0.649-0.965), P=0.020). UF, D/D(0), and D/P(Creat) changed only in those patients developing UF failure, reflecting increased membrane permeability, whereas DeltaD(Na) significantly decreased in all patients. The 3.86%-PET allows a more complete study of peritoneal membrane transport than the standard 2.27%-PET. DeltaD(Na) shows a constant and significant reduction over time and is the only factor independently predicting the risk of developing UF failure in PD patients.

Reduction in urea distribution volume over time in clinically stable dialysis patients.

We have previously shown that, assuming urea distribution volume (V) remains constant for 1 month, ionic dialysance (ID) allows the dialysis dose to be calculated without the need for blood sampling. The aim of this multicenter study was to verify whether the assumption of a constant V can be extended to 1 year. In clinically stable patients receiving thrice-weekly hemodialysis at 13 dialysis centers, V and Kt/V were assessed during three dialysis sessions at baseline and 1 year later using ID as dialyzer urea clearance and the single-pool urea kinetic model. Baseline albumin, hemoglobin, and C reactive protein were prespecified covariates for predicting the change in V over time. Of the 52 enrolled patients, 40 (25 males; age 63.0+/-13.5 years) completed the study. Baseline end-dialysis body weight (62.4+/-13.7 kg) showed a non-significant 1% reduction during follow-up (-0.6+/-2.8 kg; P=0.175), whereas V significantly decreased from 29.0+/-6.8 to 27.4+/-6.0 l (-1.6+/-3.0 l or 4.5%; P=0.002). The reduction in V was greater when baseline albumin was lower (P=0.001) and baseline V was higher (P=0.005). The single-pool K(t)/V calculated using baseline V underestimated the actual value by 0.07+/-0.16 (P=0.008). The slight underestimate of Kt/V during follow-up suggests that annual V evaluations may be sufficient for dialysis dose quantification as the only risk is underestimating the actually delivered dialysis dose. However, the relationship between baseline albumin and the reduction in V over time may have nutritional value, and suggests more frequent V evaluations.

Dialysis: its role in optimizing recombinant erythropoietin treatment.

Although iron deficiency is probably the most important factor affecting response to recombinant erythropoietin (Epo, epoetin), other factors are of significance, including dialysis adequacy. Additionally, water treatment and distribution, sterilizants and the quality of the dialysate in terms of trace elements (particularly chloramine) are of importance in relation to erythropoiesis inhibition. Microbiological or pyrogenic contamination can cause or aggravate anaemia in haemodialysis patients, and the impact of enhanced production of cytokines should be taken into consideration. By removing small and (possibly) medium/large molecules, adequate dialysis is of paramount importance in correcting anaemia and optimizing epoetin therapy. The biocompatibility of dialysis membranes and flux are other important factors. As yet unknown uraemic toxins may suppress erythropoiesis and contribute towards the development of anaemia. It is reasonable to hypothesize that, because anaemia improves after the start of dialysis with cellulose membranes, low molecular weight erythropoiesis inhibitors are involved, as well as medium/large molecular weight inhibitors, which are removed by more permeable membranes. However, in highly selected, adequately dialysed patients without iron or vitamin depletion, the effects of dialysis membrane type on haematological parameters and epoetin efficacy are smaller than might be expected from the results of uncontrolled studies. Improvement in anaemia has been observed using on-line haemofiltration, haemodiafiltration, and sterile dialysate. The results of prospective, randomized trials examining the impact of these factors on anaemia and the effectiveness of epoetin treatment are eagerly awaited.

On-line monitoring and convective treatment modalities: short-term advantages.

BACKGROUND: Despite technological advances in dialysis equipment, the morbidity and quality of life of uraemic patients undergoing regular haemodialytic treatment are still severely affected by acute intradialytic complications possibly related to the treatment itself. Cardiovascular instability still affects >30% of dialytic sessions and, although its pathogenesis is multifactorial, dialysate sodium concentration (and, consequently, intradialytic sodium removal) is one of the main factors affecting intradialytic hypotension. Convective treatment modalities and so-called biocompatible membranes increasingly are recognized as improving acute and particularly chronic dialytic complications because a number of the pathways activated in patients during dialysis with 'bioincompatible' membranes have the potential to produce many side effects. METHODS: The main clinical studies are reviewed to highlight the advantages of on-line monitoring and convective modalities on acute intradialytic symptoms. RESULTS: The conductivity kinetic model has been shown to be a reliable and inexpensive method of matching intradialytic sodium removal and interdialytic load. By applying this model to patients prone to dialysis hypotension, a smaller reduction in intradialytic systolic blood pressure has been observed, without any change in dialysate and reinfusate sodium concentrations or dry body weight. Furthermore, a new model of haemodialysis potassium removal based on a decreasing intradialytic potassium concentration and a constant plasma-dialysate potassium gradient is capable of reducing the arrhythmogenic effect of standard haemodialysis. Despite the proven biological superiority of biocompatible membranes, there is no definitive evidence that membrane biocompatibility and/or flux lead to a decrease in acute intradialytic clinical symptoms. CONCLUSIONS: On-line monitoring of intradialytic sodium removal and the potassium gradient is capable of reducing intradialytic hypotension and the arrhythmogenic effect of haemodialysis, and thus having a considerable clinical impact on acute intradialysis complications. As far as the effects of biocompatibility and/or flux on the incidence of acute intradialytic clinical symptoms are concerned, further trials involving a sicker patient population with higher prevalence of intradialytic hypotension are needed in order to achieve statistical power.

Optimization of sodium removal in paired filtration dialysis by single pool sodium and conductivity kinetic models.

Sodium removal is one of the main factors affecting intradialytic cardiovascular stability and interdialytic hypertension, and its removal should therefore be individualized. The aims of this study were: (1) to test the ability of a single-pool variable volume (SPVV) sodium kinetic model (NaKM) to optimize sodium removal in paired filtration dialysis (PFD), and (2) to test a SPVV conductivity kinetic model (CKM) in order to verify whether CKM can be used as an alternative for NaKM in estimating sodium balance. The mean difference between the NaKM-predicted and measured end-PFD plasma water ionized sodium concentrations was 0.00 +/- 0.55 mEq/l, which means that the model has an imprecision of < or = 1.1 mEq/ l. The mean difference between predicted and measured sodium removal was 0.21 +/- 16.86 mEq/session, which means a model overestimate of 0.21 mEq/session. The mean difference between the CKM-predicted and measured end-PFD ultrafiltrate conductivity was 0.01 +/- 0.05 mS/cm, which means an inaccuracy of the model of 0.01 mS/cm and an imprecision of < or = 0.1 mS/cm. The regression in the ionized sodium concentration measured in plasma or blood on the conductive values of the ultrafiltrate shows an error of < or = 2 mEq/l in the prediction of the ionized sodium concentration in blood by means of ultrafiltrate conductivity measurements. These results demonstrate that both models make it possible to obtain a level of dialytic sodium removal that is almost equivalent to interdialytic sodium loading. Moreover, given that it does not require blood sampling and the possibility of making repeated and inexpensive ultrafiltrate conductivity measurements, the CKM allows online monitoring of programmed sodium removal.