The Predialysis Serum Sodium Level Modifies the Effect of Hemodialysis Frequency on Left-Ventricular Mass: The Frequent Hemodialysis Network Trials

INTRODUCTION

The Frequent Hemodialysis Network (FHN) Daily and Nocturnal trials aimed to compare the effects of hemodialysis (HD) given 6 versus 3 times per week. More frequent in-center HD significantly reduced left-ventricular mass (LVM), with more pronounced effects in patients with low urine volumes. In this study, we aimed to explore another potential effect modifier: the predialysis serum sodium (SNa) and related proxies of plasma tonicity.

METHODS

Using data from the FHN Daily and Nocturnal Trials, we compared the effects of frequent HD on LVM among patients stratified by SNa, dialysate-to-predialysis serum-sodium gradient (GNa), systolic and diastolic blood pressure, time-integrated sodium-adjusted fluid load (TIFL), and extracellular fluid volume estimated by bioelectrical impedance analysis.

RESULTS

In 197 enrolled subjects in the FHN Daily Trial, the treatment effect of frequent HD on ∆LVM was modified by SNa. When the FHN Daily Trial participants are divided into lower and higher predialysis SNa groups (less and greater than 138 mEq/L), the LVM reduction in the lower group was substantially higher (-28.0 [95% CI -40.5 to -15.4] g) than in the higher predialysis SNa group (-2.0 [95% CI -15.5 to 11.5] g). Accounting for GNa, TIFL also showed more pronounced effects among patients with higher GNa or higher TIFL. Results in the Nocturnal Trial were similar in direction and magnitude but did not reach statistical significance.

DISCUSSION/CONCLUSION

In the FHN Daily Trial, the favorable effects of frequent HD on left-ventricular hypertrophy were more pronounced among patients with lower predialysis SNa and higher GNa and TIFL. Whether these metrics can be used to identify patients most likely to benefit from frequent HD or other dialytic or nondialytic interventions remains to be determined. Prospective, adequately powered studies studying the effect of GNa reduction on mortality and hospitalization are needed.

Recommended Clinical Practices for Maximizing Peritoneal Dialysis Clearances

Data from the Canada-U.S.A. (CANUSA) Study have recently confirmed a long-suspected linkage between total clearance and patient survival in peritoneal dialysis (PD). Recognizing that what we have historically accepted as adequate PD simply is not, the Ad Hoc Committee on Peritoneal Dialysis Adequacy met in January, 1996. This committee of invited experts was convened by Baxter Healthcare Corporation to prepare a consensus statement that provides clinical recommendations for achieving clearance guidelines for peritoneal dialysis. Through an analysis of 806 PD patients, the group concluded that adequate clearance delivered with PD can be achieved in almost all patients if the prescription is individualized according to the patient's body surface area, amount of residual renal function, and peritoneal membrane transport characteristics. Use of 2.5 L to 3.0 L fill volumes, the addition of an extra exchange, and giving automated peritoneal dialysis patients a “wet” day are all options to consider when increasing weekly creatinine clearance and KTN. Rather than specify a single clearance or KTN target, the recommended clinical practice is to provide the most dialysis that can be delivered to the individual patient, within the constraints of social and clinical circumstances, quality of life, life-style, and cost. The challenge to PD practitioners is to make prescription management an integral part of everyday patient management. This includes assessment of peritoneal membrane permeability, measurement of dialysis and residual renal clearance, and adjustment of the dialysis prescription when indicated.

Mortality risk for patients receiving hemodiafiltration versus hemodialysis: European results from the DOPPS

Hemodiafiltration (HDF) is used sporadically for renal replacement therapy in Europe but not in the US. Characteristics and outcomes were compared for patients receiving HDF versus hemodialysis (HD) in five European countries in the Dialysis Outcomes and Practice Patterns Study. The study followed 2165 patients from 1998 to 2001, stratified into four groups: low- and high-flux HD, and low- and high-efficiency HDF. Patient characteristics including age, sex, 14 comorbid conditions, and time on dialysis were compared between each group using multivariate logistic regression. Cox proportional hazards regression assessed adjusted differences in mortality risk. Prevalence of HDF ranged from 1.8% in Spain to 20.1% in Italy. Compared to low-flux HD, patients receiving low-efficiency HDF had significantly longer average duration of end-stage renal disease (7.0 versus 4.7 years), more history of cancer (15.4 versus 8.7%), and lower phosphorus (5.3 versus 5.6 mg/dl); patients receiving high-efficiency HDF had significantly more lung disease (15.5 versus 10.2%) and received a higher single-pool Kt/V (1.44 versus 1.35). High-efficiency HDF patients had lower crude mortality rates than low-flux HD patients. After adjustment, high-efficiency HDF patients had a significant 35% lower mortality risk than those receiving low-flux HD (relative risk=0.65, P=0.01). These observational results suggest that HDF may improve patient survival independently of its higher dialysis dose. Owing to possible selection bias, the potential benefits of HDF must be tested by controlled clinical trials before recommendations can be made for clinical practice.

Association of Achieved Dialysis Dose with Mortality in the Hemodialysis Study: An Example of “Dose-Targeting Bias”

In the intention-to-treat analysis of the Hemodialysis Study, all-cause mortality did not differ significantly between the high versus standard hemodialysis dose groups. The association of mortality with delivered dose within each of the two randomized treatment groups was examined, and implications for observational studies were considered. Time-dependent Cox regression was used to relate the relative risk (RR) for mortality to the running mean of the achieved equilibrated Kt/V (eKt/V) over the preceding 4 mo. eKt/V was categorized by quintiles within each dose group. Analyses were controlled for case-mix factors and baseline anthropometric volume. Within each randomized dose group, mortality was elevated markedly when achieved eKt/V was in the lowest quintile (RR, 1.93; 95% confidence interval [CI], 1.40 to 2.66; P < 0.0001 in the standard-dose group; RR, 2.04; 95% CI, 1.50 to 2.76; P < 0.0001 in the high-dose group; RR relative to the middle quintiles). The mortality rate in the lowest eKt/V quintile of the high-dose group was higher than in the full standard-dose group (RR, 1.59; 95% CI, 1.29 to 1.96; P < 0.0001). Each 0.1 eKt/V unit below the group median was associated with a 58% higher mortality in the standard-dose group (P < 0.001) and a 37% higher mortality in the high-dose group (P < 0.001). The magnitude of these dose-mortality effects was seven- to 12-fold higher than the upper limit of the 95% CI from the intention-to-treat analysis. The effects were attenuated in lagged analyses but did not disappear. When dialysis dose is targeted closely, as under the controlled conditions of the Hemodialysis Study, patients with the lowest achieved dose relative to their target dose experience markedly increased mortality, to a degree that is not compatible with a biologic effect of dose. The possibility of similar (albeit smaller) biases should be considered when analyzing observational data sets relating mortality to achieved dose of dialysis.

Dialysis dose and the effect of gender and body size on outcome in the HEMO Study

BACKGROUND

Gender and body size have been associated with survival in hemodialysis populations. In recent observational studies, overall mortality was similar in men and women and higher in small patients. The effect of dialysis dose in each of these subgroups has not been tested in a clinical trial.

METHODS

The HEMO Study was a controlled trial of dialysis dose and membrane flux in 1846 hemodialysis patients followed up for 6.6 years in 15 centers throughout the United States. We examined the effect of dialysis dose on mortality and on selected secondary outcomes in subgroups of patients.

RESULTS

Adjusting for age only, overall mortality was lower in patients with higher body weight (P < 0.001), higher body mass index (P < 0.001), and higher body water content determined by the Watson formula (Vw) (P < 0.001), but was not associated with gender (P= 0.27). The RR of mortality comparing the high dose with the standard dose group was related to gender (P= 0.014). Women randomized to the high dose had a lower mortality rate than women randomized to the standard dose (RR = 0.81, P= 0.02), while men randomized to the high dose had a nonsignificant trend for a higher mortality rate than men randomized to the standard dose (RR = 1.16, P= 0.16). Analysis of both genders combined showed no overall dose effect (R = 0.96, P= 0.52), as reported previously. Vw was greater than 35 L in 84% of men compared with 17% of women. However, the RR of mortality for the high versus standard dose remained lower in women than in men after adjustment for the interaction of dose with Vw or with other size parameters, including weight and body mass index. Conversely, the dose effect was not significantly related to size parameters after controlling for the relationship of the dose comparison with gender.

CONCLUSION

The data suggest that mortality and morbidity might be reduced by increasing the dialysis dose above the current standard in women but not in men. This effect was not explained by differences between men and women in age, race, or in several indices of body size. Because multiple comparisons were considered in this analysis, the role of gender on the effect of dialysis dose is suggestive and invites further study.

The Acute Dialysis Quality Initiative--part III: solute control (treatment dose)

One of the most important advances in chronic dialysis therapy was the establishment of a method for determining delivered dose. There has been a meaningful relationship between higher delivered dialysis dose and improved outcome in the end-stage renal disease (ESRD) patient. The question of establishing a similar dialysis dose method in the patients with acute renal failure (ARF) is hampered with several specific issues to the ARF patient. The state of catabolism in ARF is not eubolic, but rather catabolic. Patient volume or urea space is highly variable among ARF patients and even within the same patient over very short periods of time. Finally, there are comorbidities that play a major role in both the ultimate patient outcome and the generation of many of the indicators used in dialysis dose generation. Thus, the mere transition from the ESRD dose methodology, where these issues are quite stable, to the ARF population is not an easy process. It is, however, of utmost importance that a dose methodology be established. Only after will we be able to address the dose/outcome relationship. The current article reviews what is known, what is theorized and what needs to be established in an effort to determine a dialysis dose methodology in ARF patients.

Lessons from the Hemodialysis (HEMO) Study: an improved measure of the actual hemodialysis dose

The Hemodialysis (HEMO) Study is a multicenter, prospective, randomized, 2 x 2 factorial clinical trial designed to evaluate the efficacy of the dose of dialysis delivered ("standard" v "high") and dialysis membrane flux ("low" v "high") in reducing the morbidity and mortality of patients. The study is nearly half complete. Although both patients and investigators are blinded to the overall findings, which will not be available for another 3 years, important data have been generated from which a more accurate expression has been derived for the dose of dialysis received by each patient in the trial. This new expression of the effectiveness of dialysis, eKt/V, is a two-pool approximation derived from the traditional single-pool Kt/V (spKt/V) and time on dialysis. The dialysis prescription for the HEMO Study subjects is individualized to achieve the target dose for each patient and is closely monitored by measuring the more accurate and validated expression of eKt/N. Comparisons of the HEMO Study dose of dialysis with other studies have been confused by this unique expression (eKt/V) of the dialysis dose and adequacy adopted for the HEMO Study. The target eKt/V dose in the "standard" arm of the Study is 1.05 and in the "high" arm is 1.45 per dialysis thrice weekly. Based on data available from 426 subjects randomized to each arm, the target of 1.05 in the "standard" dose of the HEMO Study is equivalent to an spKt/V of 1.32, and that of the "high" dose, 1.67. Thus, volunteers in the "standard" arm of the Study are receiving a tightly controlled and closely monitored dose, which is above the current national mean spKt/V, and above that of the accepted minimum standard spKt/N of 1.2. When completed, the HEMO Study will show whether there are merits of a tightly controlled hemodialysis dose that is consistently delivered over a prolonged period and whether a high dose is beneficial and safe to prescribe.

Albumin synthesis, catabolism and distribution in dialysis patients

Hypoalbuminemia predicts mortality in hemodialysis patients with end-stage renal disease (ESRD) and is assumed to result from malnutrition. We report here that plasma albumin levels are reduced significantly in both hemodialysis and peritoneal dialysis (PD) patients compared to normal subjects. Among hemodialysis patients with normal albumin levels (the upper quartile of albumin distribution), albumin synthesis rates, fractional catabolic rates, and distribution between the vascular and extravascular pool are normal, suggesting that ESRD per se does not derange albumin metabolism. Albumin synthesis is reduced in hemodialysis patients who are hypoalbuminemic, but the fractional albumin catabolic rate decreases normally, and albumin distribution between the vascular and extravascular space remains normal, suggesting that hypoalbuminemia results primarily from decreased synthesis. Using multiple linear regression analysis, the strongest correlates to plasma albumin concentration in 115 hemodialysis patients were the plasma level of the acute-phase C-reactive protein (CRP) and the normalized protein catabolic rate (PCRn). These two independent predictors of plasma albumin concentrations are markers of inflammation and of protein intake, respectively. CRP levels correlate more strongly with albumin concentration than does low PCRn. Activity of the acute-phase response is an important predictor of low plasma albumin concentration in hemodialysis patients independently of nutritional factors. External loss of albumin in the dialysate is an additional factor that contributes significantly to hypoalbuminemia in PD patients.

Recommended clinical practices for maximizing peritoneal dialysis clearances

Data from the Canada-U.S.A. (CANUSA) Study have recently confirmed a long-suspected linkage between total clearance and patient survival in peritoneal dialysis (PD). Recognizing that what we have historically accepted as adequate PD simply is not, the Ad Hoc Committee on Peritoneal Dialysis Adequacy met in January, 1996. This committee of invited experts was convened by Baxter Healthcare Corporation to prepare a consensus statement that provides clinical recommendations for achieving clearance guidelines for peritoneal dialysis. Through an analysis of 806 PD patients, the group concluded that adequate clearance delivered with PD can be achieved in almost all patients if the prescription is individualized according to the patient's body surface area, amount of residual renal function, and peritoneal membrane transport characteristics. Use of 2.5 L to 3.0 L fill volumes, the addition of an extra exchange, and giving automated peritoneal dialysis patients a "wet" day are all options to consider when increasing weekly creatinine clearance and KT/V. Rather than specify a single clearance or KT/V target, the recommended clinical practice is to provide the most dialysis that can be delivered to the individual patient, within the constraints of social and clinical circumstances, quality of life, life-style, and cost. The challenge to PD practitioners is to make prescription management an integral part of everyday patient management. This includes assessment of peritoneal membrane permeability, measurement of dialysis and residual renal clearance, and adjustment of the dialysis prescription when indicated.

Mesangial glomerulopathy and IgM rheumatoid factor in rheumatoid arthritis

Hematuria and proteinuria in rheumatoid arthritis (RA) are commonly associated with drug therapy but occur independently of drugs, amyloid or urologic disorders. The latter occurrences suggest a primary renal lesion associated with RA. Review of reported renal biopsies identifies mesangial glomerulopathy as a common finding in RA patients without associated drug therapy and that it is frequently associated with hematuria in nonrheumatoid patients. Moreover, immunoglobulins have been shown to concentrate in the mesangium in experimental animals, suggesting that a functional response by the kidney mesangium to remove IgM rheumatoid factor (RF)-IgG complexes could lead to this mesangial lesion. We describe 3 patients with RA who had a mesangiopathy characterized by increased quantities of mesangial matrix and deposition of IgM without other lesions. Together, these observations suggest that: (1) mesangial glomerulopathy is common in RA; (2) removal of circulating RF-IgG complexes is a function of the mesangium and might produce this renal lesion; (3) mesangial glomerulopathy may be responsible for much of the hematuria observed in RA patients and, in many cases, may not be drug related and thus may not require discontinuing beneficial therapy.

Plasma hippurate in renal failure: high-performance liquid chromatography method and clinical application

We have developed a high-performance liquid chromatography (HPLC) method for assay of hippurate in plasma of patients with renal failure. Hippurate accounts, in part, for the impaired binding of drugs and metabolites to albumin and may cause other disorders in azotemic patients. The method is precise, accurate and reproducible. Among 25 patients with acute and chronic renal failure having serum creatinine in the range of 2.9-43 mg/dl (256-3,801 mumol/l), plasma hippurate ranged from 0.11 to 16.2 mg/dl (6.1-904 mumol/l). Hippurate concentration correlated moderately closely with plasma creatinine, urea and anion gap. Its curvilinear relation to the reciprocal of serum creatinine indicated a proportional decline of GFR and tubular function or the accumulation of inhibitors of the proximal tubular anion secretory pathway. The method should be useful for further studies of abnormal albumin binding as well as other disorders in azotemic patients.

Immobilization hypercalcemia: a case report and review of the literature

A 17-year-old girl was immobilized in traction for 3 months and in a spica cast for 6 weeks for fractures of the femur and pelvis. Seven weeks after injury and after her acute renal failure had resolved, serum calcium rose and remained elevated for the duration of her immobilization. Conservative treatment by hydration, diuresis, and later tilttable therapy failed to relieve her hypercalcemia. Only after mobilization did the serum calcium levels return to normal and the symptoms abate. Administration of recently developed medical methods of management of hypercalcemia may have prevented this complication.

Erythrocytosis associated with diffuse parenchymal lesions of the kidney

Thirteen patients with diffuse parenchymal disease of the kidney and erythrocytosis are reported. In five the haematocrit was only minimally elevated because of an associated increase in plasma volume. The erythrocytosis in three patients was of particular interest: (1) transient appearance in a 23-year-old man with glomerulonephritis; (2) persistence despite the partial remission of nephrotic state in a 19-year-old man; (3) appearance following removal of a nephrosclerotic kidney from a 54-year-old woman. Because an associated expansion of plasma volume is not uncommon with parenchymal renal disease, it is suggested that the only reliable screening method for renal erythrocytosis is direct measurement of red cell volume.