Monitoring hemodialysis dose with ionic dialisance in on-line hemodiafiltration

Until now, with the ionic dialysance measurement, it has been possible to determine hemodialysis dose in each session of hemodialysis (HD) and in the conventional hemofiltration (HDF) but not in the modality of on-line HDF. Recently it is possible with a new biosensor that allows to measure the dose in on-line HDF. The aim of this study was to evaluate the value of this biosensor in different dialysis situations comparing the dialysis dose measured in blood in comparison with the values obtained from the sensor. We have analysed 192 hemodialysis sessions performed in 24 patients, 15 male and 9 female, mean age of 70.2 +/- 12 years, included in on-line HDF. All treatments were done using 4008H (Fresenius) monitor equipped with on-line clearance monitoring (OCM), that measure, with non invasive monitoring, the effective ionic dialysance equivalent to urea clearance. Every patient received eight dialysis sessions: one with dialysate flow (Qd) 500 ml/min, two with HD and Qd 800 ml/min and five with on-line HDF. Other habitual haemodialysis parameters were no changed, dialysis time 200 +/- 63 min (135-300) and blood flow 421 +/- 29 ml/min (350-450). Initial and final ionic dialysance values (K), final Kt, Kt/V measured with OCM using V of Watson, and Kt/V determined in blood pre and postdialysis concentrations of urea (Daugirdas second generation), were measured. The mean of initial K was 251 +/- 21 ml/min and the final K was 234 +/- 24 ml/min. The Kt measured with OCM was 50.6 +/- 17 L, 51.2 +/- 17 in men and 49.7 +/- 16 in women. The V (Watson) was 34.5 +/- 6 L. The Kt/V measured with the Kt of OCM and V was 1,499 +/- 0.54 and Kt/V measured in blood samples was 1,742 +/- 0.58. The correlation between both values was 0.956. The Kt was different according to dialysis modality used: in HD and Qd 500 was 44.7 +/- 15 L, in HD and Qd 800 was 50.7 +/- 17 and in on-line HDF (22.1 +/- 7 L of reposition volume), was 51.8 +/- 17 L. The Kt/V from blood samples also shows variation: in HD and QD 500 was 1.60 +/- 0.55, in HD and Qd 800 was 1,726 +/- 0.56 and in on-line HDF was 1,776 +/- 0.59. In this study has been observed a close correlation between the new biosensor OCM with the measures obtained from the blood samples. For this reason this sensor it is useful in all modalities of dialysis treatment, included on-line HDF. The sensor was able to discriminate the efficacy of different dialysis modalities used in this study.     

ON‐LINE CLEARANCE MONITORING FOR BLOOD ACCESS MANAGEMENT

On‐line Clearance Monitoring (OCM) provides frequent and precise information about urea clearance values during haemodialysis. In the case of blood access recirculation, it is presumed that urea clearance values on OCM would be lower and suspect to blood access malfunction. In order to check the relation between significantly lower urea clearance values and blood access recirculation, the Kt value (Clearance × time/min) for fifteen patients on OCM, including the patients with a low Kt/V in spite of their small urea distribution volume (V) was observed. Average urea clearance was calculated indirectly using Kt value (Kt/time in minutes = average clearance ml/min) and blood access recirculation tests performed using slow/stop flow two‐needle, three samples method (urea method). After comparison of the recirculation percentage to clearance value, positive correlation between high recirculation and clearance reduction was noted. OCM alongside detection of haemodialysis inefficiency is also a practical instrument for blood access management between regular monitoring. Lower OCM urea clearance values demonstrate a possible blood access problem that can be confirmed with another method. When an OCM urea clearance reading is decreased by more than 25%, undiscovered access recirculation can be suspected.     

On-line clearance monitoring for blood access management

On-line Clearance Monitoring (OCM) provides frequent and precise information about urea clearance values during haemodialysis. In the case of blood access recirculation, it is presumed that urea clearance values on OCM would be lower and suspect to blood access malfunction. In order to check the relation between significantly lower urea clearance values and blood access recirculation, the Kt value (Clearance x time/min) for fifteen patients on OCM, including the patients with a low Kt/V in spite of their small urea distribution volume (V) was observed. Average urea clearance was calculated indirectly using Kt value (Kt/time in minutes = average clearance ml/min) and blood access recirculation tests performed using slow/stop flow two-needle, three samples method (urea method). After comparison of the recirculation percentage to clearance value, positive correlation between high recirculation and clearance reduction was noted. OCM alongside detection of haemodialysis inefficiency is also a practical instrument for blood access management between regular monitoring. Lower OCM urea clearance values demonstrate a possible blood access problem that can be confirmed with another method. When an OCM urea clearance reading is decreased by more than 25%, undiscovered access recirculation can be suspected.     

The influence of varying blood and dialysate flow on haemodialysis adequacy

The aim of this study was the exploration and correlation of the influence of variations in blood flow and dialysate flow on haemodialysis adequacy through the quantitative indexes Kt/V, TACurea and PCR. A prospective study of 48 patients subjected to haemodialysis was carried out. The collection of data included taking blood and urine samples according to the directives of DOQI, for a total of 8 months. Statistical analysis was based on the paired t-test and multiple regression analysis. The variations in blood flow and dialysate flow are positively related to the variation of the indexes Kt/V, TACurea and PCR and consequently to the haemodialysis adequacy both as isolated factors and when combined together.     

Estimate of the dialysis dose using ionic dialysance

The Diascan equipment (Hospal) measures ionic dialysance from which it derives the Kt/V. It is automatic, does not need blood samples and displays the results in real time. The aim of the present study was to compare the Diascan Kt/V with the Kt/V obtained with four simple formulas: two based on a single pool model of urea kinetics (Lowrie 1983 and Daugirdas 1993) and the other based on the two pool model (Maduell formulation applied to Lowrie Kt/V and that proposed by Daugirdas 1995). We have analyzed the inter-method variability, the degree of relationship among the different procedures for Kt/V calculation and the intra-individual variability. The intermethod variability between Kt/V Diascan and Kt/V calculated by the four simple formulas were studied in one hemodialysis session in 19 patients. The Kt/V Diascan was statistically different from that calculated by the four formulas (1,021 +/- 0.140 Diascan vs 1,147 +/- 0.124 for Lowrie-83; vs 1,373 +/- 0.164 for Daugirdas-93; vs 0.963 +/- 0.105 for Maduell and vs 1,173 +/- 0.143 for Daugirdas-95, p < 0.01). The lowest inter-method variability was obtained with the Maduell's Kt/V (relative difference 9%) but even in this case 37% of patients had a variability above 10%. The correlation coefficient was not high enough to allow an estimation of the different Kt/V measurements from the Diascan Kt/V by a regression equation. To study the individual relationship between the Diascan Kt/V and the Kt/V calculated by the four formulations, we have determined the Kt/V every 30 minutes in one hemodialysis session in 30 patients. In all patients we observed a good relationship between the Diascan Kt/V and the other four (correlation coefficient of 0.9952 for Lowrie-83, 0.9976 for Daugirdas-93, 0.9961 for Maduell and 0.9971 for Daugirdas-95); with these correlation coefficientes it was possible to derive regression equations and to obtain an estimation of the four Kt/V's from the Diascan Kt/V. To study the individual variability of each procedure used in the Kt/V calculations we determined the coefficient of variation of the different methods in 5 consecutive hemodialysis sessions performed under identical conditions in 19 patients. The coefficient of variation was 3.7 +/- 1.8% for the Diascan Kt/V; 6.0 +/- 2.8 for the Lowrie-83 Kt/V; 5.8 +/- 2.4 for the Daugirdas-93 Kt/V; 6.5 +/- 2.6% for the Maduell Kt/V; and 5.7 +/- 2.2% for the Daugirdas-95 Kt/V (p < 0.01 between the Diascan Kt/V and the other four). CONCLUSIONS: Although the Diascan Kt/V was statistically different from the other four Kt/V's calculated by the usual formulas, the Diascan Kt/V has an excellent correlation with all of them and showed a lower intra-individual variability. It is possible to obtain an estimation of the calculated Kt/V for each patient by linear regression equation.     

CONVENTIONAL BLOOD SAMPLING VERSUS ON‐LINE CLEARANCE MONITORING

On‐line Clearance Monitoring (OCM) calculates the Kt/V during a dialysis session using a module incorporated into the Fresenius 4008 H/S haemodialysis machine     

Determination of the dose of dialysis with integrated modules in the same monitor

The "gold standard" method to measure the mass balance achieved during dialysis for a given solute is based on the total dialysate collection. This procedure is unfeasible and too cumbersome. For this reason, alternative methods have been proposed including the urea kinetic modelling (Kt/V), the measurement of effective ionic dialysance (Diascan), and the continuous spent sampling of dialysate (Quantiscan). The aim of this study was to compare the reliability and agreement of these two methods with the formulas proposed by the urea kinetic modelling for measuring the dialysis dose and others haemodialysis parameters. We studied 20 stable patients (16 men/4 women) dialyzed with a monitor equipped with the modules Diascan (DC) and Quantiscan (QC) (Integra. Hospal). The urea distribution volume (VD) was determined using anthropometric data (Watson equation) and QC data. Kt/V value was calculated according to Daurgidas 2nd generation formula corrected for the rebound (eKt/V), and using DC (Kt/VDC) and QC (Kt/VQC) data. The total mass of urea removed was calculated as 37,93 +/- 16 g/session. The VD calculated using Watson equation was 35.7 +/- 6.6 and the VDQC was 35.06 +/- 9.9. And they showed an significative correlation (r:0,82 p < 0.001). The (VDQC-VDWatson) difference was -0.64 +/- 5.8L (ns). Kt/VDC was equivalent to those of eKt/V (1.64 +/- 0.33 and 1.61 +/- 0.26, mean difference -0.02 +/- 0.29). However, Kt/VQC value was higher than eKt/V (1.67 +/- 0.22 and 1.61 +/- 0.26 mean difference 0.06 +/- 0.07 p < 0.01). Both values correlated highly (R2: 0.92 p < 0.001). Urea generation (C) calculated using UCM was 8.75 +/- 3.4 g/24 h and those calculated using QC was 8.64 +/- 3.21 g/24 h. Mean difference 0.10 +/- 1.14 (ns). G calculated by UCM correlated highly with that derived from QC (R2: 0.88 p < 0.001). In conclusion, Kt/VDC and Kt/VQC should be considered as valid measures for dialysis efficiency. However, the limits of agreement between Kt/VQC and eKt/V were closer than Kt/VDC.     

Ionic dialysance to control the dose of dialysis. One year experience

The Diascan equipment (Hospal) measures ionic dialysane which it derives the K and the Kt. If we divide the Kt obtained with Diascan between the Kt/V obtained by a simplified formula, it result a value of V for every patient. Entering this V in the Diascan software we can obtain a Kt/V (Diascan Kt/V), similar in theory to the simplified Kt/V. In the year 2002 we have controlled the delivered dialysis in our unit with the Diascan Kt/V. The aim of the present study was to study the agreement between de Diascan Kt/V and the Lowrie Kt/V. During the year 2002, 63 patients have been dialyzed in monitors with Diascan equipment. We calculated the V of each patient by dividing the Kt Diascan between the Lowrie Kt/V in the same dialysis session. The mea of the two consecutive measurements was considered the V value. Throughout the year 2002, 7 agreement studies were realized. The inter-method variability was assessed by the relative difference (absolute difference Diascan Kt/V-Lowrie Kt/V, divided by the average of both tests). A good agreement was considered when the relative difference was equal or lower than 10%. In the 7 agreement studies realized, the mean of the relative difference oscilled between 5.2 and 6.6%, and the percentage of patients with a relative difference equal or lower than 10% oscilled between 83 and 91%. During a month, the Diascan Kt/V was controlled in all dialysis sessions in 41 patients (554 sessions in total). Failure in the lecture of Kt/V Diascan was observed in 41 sessions (7%). A Diascan Kt/V greater than 1 (the minimum delivered dialysis considered in our unit) was obtained in 93% of the valid sessions. 38 of 41 patients had a mean monthly Diascan Kt/V greater than 1. The coefficient of variability of any patient oscilled between 2.1 and 12.4% (mean 5.1%). Diascan Kt/V is good procedure for the monitoring the delivered dialysis without blood sampling or any additional costs.     

Update on Postdialysis Rebound by a New Technology in Hemodialysis

After dialysis ends, urea continued movement causes rebound postdialysis, with values at about 20%. New techniques have been incorporated into hemodialysis, but their relationship with rebound has not yet been studied. This study aimed to quantify urea rebound at 30‐min postdialysis during sessions using polysulfone filters and high‐flow versus online hemodiafiltration, and to define its correlation with body composition measured by bioimpedance by a cross‐sectional study with 69 patients (December 2015 to January 2016). Mean urea rebound was 24.39, which was positively associated with recirculation, Kt/V or hypotension, and showed a negative relationship with online hemodiafiltration. It was not associated with different body composition compartments. To conclude, postdialysis urea rebound remained high with polysulfone dialyzers and low dialysis doses. Online hemodiafiltration could improve postdialysis urea rebound. Different body composition compartments were not related to rebound.     

Ionic dialysance and quality control in hemodialysis

Quantification of dialysis is based on the measurement of effective urea clearance (K), dialysis dose (Kt) or normalized dialysis dose (Kt/V). During the last 20 years, Kt/V was the single parameter actually useful for quantifying dialysis efficiency, because it can be calculated from just blood or dialysate urea concentrations at the beginning and at the end of the dialysis session. However the calculation of the normalized dialysis dose (Kt/V) actually delivered to the patient cannot be performed during each dialysis session, because of the need of urea concentration measurements. Ionic dialysance is a new parameter easily measured on-line, non-invasively, automatically and without any cost during each dialysis session by a conductivity method. Because ionic dialysance has been proved equal to the effective urea clearance taking into account cardiopulmonary and access recirculation, it is becoming an actual quality-assurance parameter of the dialysis efficiency.     

Measurement of backfiltration rates during hemodialysis with highly permeable membranes.

A method for determining local transmembrane fluid movement in a commercial hemodialyzer at low dialysate flow rates by measuring changes along the dialyzer length in the local concentration of a marker macromolecule added to the dialysis solution has been developed. The method was evaluated in vitro at zero net ultrafiltration using dialyzers containing polysulfone (n = 4) and cuprophane (n = 3) membranes. The local concentration of the marker macromolecule along the dialyzer length was higher than the input dialysate concentration only during experiments with dialyzers containing polysulfone membranes. These observations provide direct empirical evidence that fluid movement in the dialysate to blood direction, i.e., backfiltration, occurs during hemodialysis with this highly permeable membrane. Net rates of backfiltration for the dialyzer containing polysulfone membrane were also calculated from changes in the local concentration of the marker macromolecule and mass balance considerations. The calculated backfiltration rates increased with increasing blood flow rate and trended upward with increasing dialysate flow rate. The described methodology provides a novel approach for the further characterization of fluid and solute transport during hemodialysis with highly permeable membranes.     

El Kt/V alto,a diferencia del Kt,se asocia a mayor mortalidad: importancia de la V baja

Introduction

Kt/V has been used as a synonym for haemodialysis dose. Patient survival improved with a Kt/V > 1; this target was subsequently increased to 1.2 and 1.3. The HEMO study revealed no significant relationship between Kt/V and mortality. The relationship between Kt/V and mortality often shows a J-shaped curve. Is V the confounding factor in this relationship? The objective of this study is to determine the relationship between mortality and Kt/V, Kt and body water content (V) and lean mass (bioimpedance).

Arterial hypertension in the hemodialysis patient. A model of salt-sensitive hypertension in man]

In uremic patient treated by hemodialysis (HD), a low potassium intake and a salt load due to diet and or a high sodium concentration in dialysate are often associated to refractory hypertension. Numerous reports in general population, based on epidemiologic and demographic data, have pointed to the relationship between sodium intake and hypertension. The degree of blood pressure fall in patients who have evidence of salt-sensitivity varies directly with the severity of the hypertension, being most prominent in those with higher pressures. Recent studies have suggested that a reduction of dialysate sodium can control hypertension in maintenance haemodialysis patients. In this study, five hypertensive haemodialysis patients were assigned to a regime of lowering the dialysate sodium concentration from 142 to 135 mmol/L in combination with an attempt to lower salt intake by advising the patients to eat a NaCl-restricted diet of no more than 6-8 g/day. During the period under study, dialysis time was kept constant. A significant increase of ultrafiltrate sodium concentration was observed during the first week after lowering the dialysate sodium concentration. Post dialysis systolic and diastolic pressures showed a clear trend to fall (systolic pressure 174 +/- 18 vs 118 +/- 13 mmHg, diastolic pressure 96 +/- 7 vs 75 +/- 13 mmHg) without a change of dry weight. The reduction of the mean arterial pressure on 48 h was demonstrated with ambulatory blood pressure recording. The results of this study suggest that reducing the dialysate sodium concentration lead to a decrease in peripheral resistance. A link between sympathetic overactivity as it is found in haemodialysis patients and sodium load could be a stimulating hypothesis. It is concluded that increasing dialysate sodium in short dialysis is responsible for the high prevalence of arterial hypertension often insufficiently controlled by antihypertensive medication. In hemodialysis patients with refractory hypertension, the lowering of the dialysate sodium concentration is indicated.     

Does dialysis therapy improve autonomic and peripheral nervous system abnormalities in chronic uraemia?

OBJECTIVES: Autonomic nervous system (ANS) dysfunction and peripheral neuropathy occur in patients with chronic renal insufficiency. Adequate renal replacement therapy should prevent development or correct these abnormalities. DESIGN AND SUBJECTS: We studied retrospectively ANS and peripheral neuropathy in 32 patients with chronic uraemia who received either haemodialysis (16) or peritoneal dialysis (16) therapy, and compared the observed dialysis efficiency with changes in neurological function. METHODS: Heart rate variability (HRV) time domain indices and peripheral sensory nerve conduction studies were followed for a mean of 2.9 years. The adequacy of haemodialysis (HD) efficiency was estimated by Kt/V, an index of fractional urea clearance. Adequacy of continuous ambulatory peritoneal dialysis (CAPD) was estimated on the basis of the patient's wellbeing and nutritional status as excellent, satisfactory or poor. Based on observed changes in HRV time domain measures, the observations were divided in three subgroups: improved, unchanged or deteriorated. RESULTS: The peripheral sensory nerve conduction studies were abnormal in 38% of the patients and did not change significantly during the study. Improvement in HRV time domain measures occurred in HD patients with mean Kt/V > 1.20 or in CAPD patients with satisfactory or excellent response to dialysis treatment. Values of Kt/V < 0.85 in HD patients were associated with progressive deterioration of autonomic neuropathy. Diabetic patients (n = 4) differed from others as their HRV was grossly abnormal and did not improve. CONCLUSIONS: The adequacy of haemodialysis is a predictor of improvement of cardiac autonomic nervous function in chronic uraemia. The same trend of improvement was seen also in CAPD patients.     

The effect of profiling dialysate sodium and ultrafiltration on patient comfort and cardiovascular stability during haemodialysis

The aim of this study was to investigate what affect profiling dialysate sodium and ultrafiltration rate had on cardiovascular stability during haemodialysis, and if there was any effect on patients' fluid balance, thirst, serum sodium levels, blood pressure, or comfort and tolerance. The past decade has seen major advances in haemodialysis machine technology. Parallel developments have included profiling dialysate sodium levels and fluid removal during dialysis. However, some dialysis centres do not use profiling due to fears of long-term detrimental effects, especially with regard to hypertension and fluid control. Within my own workplace, approximately 30% of haemodialysis treatments utilise either sodium or ultrafiltration profiling, or a combination of both. Anecdotally, we have seen an increase in cardiovascular stability and haemodialysis tolerance. The aim of this study was to identify the effects of profiling haemodialysis, to ensure that the treatment we offer patients is safe and effective.     

Kt as control and follow-up of the dose at a hemodialysis unit

To ensure our patients are receiving an adequate dose in every dialysis session there must be a target to achieve this in the short or medium term. The incorporation during the last years of the ionic dialysance (ID) in the monitors, has provided monitoring of the dialysis dose in real time and in every dialysis session. Lowrie y cols., recommend monitoring the dose with Kt, recommending at least 40 L in women and 45 L in men or individualizing the dose according to the body surface area. The target of this study was to monitor the dose with Kt in every dialysis session for 3 months, and to compare it with the monthly blood test. 51 patients (58% of our hemodialysis unit), 32 men and 19 women, 60.7+/-14 years old, in the hemodialysis programme for 37.7+/-52 months, were dialysed with a monitor with IC. The etiology of their chronic renal failure was: 3 tubulo-interstitial nephropathy, 9 glomerulonephritis, 12 vascular disease, 7 polycystic kidney disease, 7 diabetic nephropathy and 13 unknown. 1,606 sessions were analysed during a 3 month period. Every patient was treated with the usual parameters of dialysis with 2.1 m2 cellulose diacetate (33.3%), 1.9 m2 polisulfone (33.3%) or 1.8 m2 helixone, dialysis time of 263+/-32 minutes, blood flow of 405+/-66, with dialysate flow of 712+/-138 and body weight of 66.7+/-14 kg. Initial ID, final ID and Kt were measured in each session. URR and Kt/V were obtained by means of a monthly blood test. The initial ID was 232+/-41 ml/min, the final ID was 197+/-44 ml/min, the mean of Kt determinations was 56.6+/-14 L, the mean of Kt/V was 1.98+/-0.5 and the mean of URR was 79.2+/-7%. Although all patients were treated with a minimum recommended dose of Kt/V and URR when we used the Kt according to gender, we observed that 31% of patients do not get the minimum dose prescribed (48.1+/-2.4 L), 34.4% of the men and 26.3% of the women. If we use the Kt individualized for the body surface area, we observe that 43.1% of the patients do not get the minimum dose prescribed with 4.6+/-3.4 L less than the dose prescribed. We conclude that the monitoring of dialysis dose with the Kt provides a better discrimination detecting that between 30 and 40% of the patients perhaps do not get an adequate dose for their gender or body surface area.     

Influence of post haemodialysis sampling on Kt/V result

The recommended Kt/V is 1.2. Unfortunately there is no written policy for nurses on the procedure for taking blood urea nitrogen samples post haemodialysis. The aim of this study was to establish the Kt/V variability of haemodialysis patients depending on the method of collection of post-haemodialysis blood urea nitrogen. Twenty-two patients were analysed. A Kt/V was performed every 15 days during a period of 2 months. It was taken five times on each patient: 30 minutes before the end of a haemodialysis session (Kt/V30), at the end of haemodialysis (Kt/V1), after slowing flows (50 ml/min) for 2 minutes (Kt/V2) and after the blood circuit had been returned to the patient at 5 and 15 minutes respectively. (Kt/V5, Kt/V15). The Kt/V results were: Kt/V1 1.23 +/- 0.2 Vs Kt/V2 1.14 +/- 0.19 (p < 0.003); Kt/V5- 1.05 +/- 0.19 (p < 0.002 Vs Kt/V2); Kt/V15 1 +/- 0.16 (p < 0.05 Vs Kt/V5); Kt/V30 1.12 +/- 0.21 (pNS Vs Kt/V2). In conclusion, there was a large variability in the Kt/V depending on the method of collection of the blood urea nitrogen sample post-haemodialysis.     

Correlates of urea kinetic modeling during hemodialysis in patients with acute renal failure

The current guidelines on dialysis adequacy in acute renal failure (ARF) are loosely defined and have been extrapolated from patients with end-stage renal disease. The objectives of this study were (1) to compare three methods of urea kinetic modeling measurement in patients with ARF receiving intermittent hemodialysis, (2) to compare prescribed to delivered dose of dialysis, and (3) to explore the factors that are associated with dialysis delivery. 'Single-pool' urea kinetic modeling was assessed by the Ureakin) software and the second-generation equation which uses a logarithmic estimate of spKt/V. 'Equilibrated' Kt/V (eKt/V) was calculated using the rate adjustment equation. The prescribed dose was derived using the manufacturer's specifications of the dialyzer clearance, prescribed time, actual delivered blood and dialysate flow, and estimates of volume of urea distribution. A total of 78 consecutive spKt/V measurements were obtained in 24 patients. The mean urea reduction ratio was 51 +/- 1%. The delivered spKt/V was significantly lower than that prescribed (0.87 +/- 0.03 or 0.83 +/- 0.03 vs. 1.28 +/- 0.05; p = 0.0001). The equilibrated Kt/V was markedly lower than the delivered spKt/V (0.73 +/- 0.03 vs. 0.83 +/- 0.03; p = 0.0001). Univariate analyses demonstrated that female gender, low body mass index, low predialysis weight, use of cellulose acetate dialyzers, and increased prescribed time were associated with increased odds of prescribed spKt/V > or =1.2. Similarly, old age, increased delivered time, and high cytokine production were associated with increased odds of delivered spKt/V > or =1.2. In summary, while the impact of delivered intermittent hemodialysis on the survival of patients with ARF remains to be determined, these results indicate that dialysis delivery is suboptimal in ARF, and empiric dosing should strongly consider factors related to lean body mass, including age and gender.