Estimating total small solute clearance in patients treated with continuous ambulatory peritoneal dialysis without urine and dialysate collection

BACKGROUND

International Society for Peritoneal Dialysis guidelines recommend to routinely monitor the total measured clearance (mCl) of small solutes such as creatinine; however, collection of 24-h urine and peritoneal dialysis (PD) fluid is burdensome to patients and prone to errors. We hypothesized that equations could be developed to estimate mCl (estimated clearance (eCl)) using endogenous filtration markers.

METHODS

In the Guangzhou PD Study (n = 980), we developed eCl equations using linear regression in two-third and validated them in the remaining one-third. Reference tests were mCl for urea nitrogen (UN) (mCl_UN, ml/min) and average mCl for UN and creatinine (mCl_UN-cr, ml/min/1.73 m²). Index tests were various eCl equations using UN, creatinine, low-molecular-weight proteins (LMWPs) (beta-trace protein (BTP), beta-2 microglobulin (B2M), and cystatin C), demographic variables, and body size. After reexpression of the equations in the combined data set, we analyzed accuracy (eCl within ± 2.0 units of mCl) and the predictive value of eCl to detect a weekly total standard Kt/V (weekly mCl_UN indexed for total body water) > 1.7 using receiver operating characteristic curve.

RESULTS

Mean age of the cohort was 50 ± 15 years, 53% were male; mCl_UN was 6.9 ± 1.8 and mCl_UN-cr was 7.5 ± 2.8. Creatinine but not UN contributed to eCl for both mCl. LMWP did not improve accuracy for mCl_UN (range 88-89%). BTP and B2M improved the accuracy for mCl_UN-cr (82% vs. 80%); however, differences were small. The area under the curve for predicting a weekly Kt/V > 1.7 was similar for all equations (range 0.79-0.80).

CONCLUSIONS

Total small solute clearance can be estimated moderately well in continuous ambulatory PD patients using serum creatinine and demographic variables without urine and dialysate collection.

Effects of fish oil during hemodialysis on nutritional status and quality of life: a randomized double-blinded trial

Background

Supplementation of fish oil has been shown to exert beneficial effects in patients undergoing hemodialysis. The aim of this study was to investigate the efficacy of fish oil in improving the quality of life of these patients through a randomized, double-blinded clinical trial.

Methods

Among the 103 patients enrolled in the study, a total of 74 patients were randomized to receive fish oil (intervention group) or placebo (n=37 per group). Patients received identical soft-gel capsules, with each capsule containing either 1000 mg fish oil or placebo for 4 months. Personnel responsible for data collection and analyses were blinded to the grouping.

Results

The reduction of protein-energy wasting (PEW) in the intervention group was significantly more prominent compared to the placebo group (P=0.023). The intervention group demonstrated significant increase in midarm circumference, arm muscle circumference, and triceps skinfold thickness after fish oil intake. The intervention group also exhibited significant differences from the placebo group in creatinine, uric acid, and serum calcium levels. Significant improvement was seen regarding the physical role and energy/figure in the intervention group.

Conclusions

Our study demonstrated that fish oil intake in patient undergoing hemodialysis can significantly reduce PEW, and improve physical and biochemical parameters and quality of life, which could provide guidance to clinical management of these patients.

Calculation of the clearance requirements for the development of a hemodialysis-based wearable artificial kidney

Wearable artificial kidney (WAK) has been considered an alternative to standard hemodialysis (HD) for many years. Although various novel WAK systems have been recently developed for use in clinical applications, the target performance or standard dose of dialysis has not yet been determined. To calculate the appropriate clearance for a HD-based WAK system for the treatment of patients with end-stage renal disease with various dialysis conditions, a classic variable-volume two-compartment kinetic model was used to simulate an anuric patient with variable target time-averaged creatinine concentration (TAC), daily water intake volume, daily dialysis pause time, and patient body weight. A 70-kg anuric patient with a HD-based WAK system operating for 24 h required dialysis clearances of creatinine of at least 100, 50, and 25 mL/min to achieve TACs of 1.0, 2.0, and 4.0 mg/dL, respectively. The daily water intake volume did not affect the clearance required for dialysis under various conditions. As the pause time per day for the dialysis increased, higher dialysis clearances were required to maintain the target TAC. The present study provided theoretical dialysis doses for an HD-based WAK system to achieve various target TACs through relevant mathematical kinetic modeling. The theoretical results may contribute to the determination of the technical specifications required for the development of a WAK system.

Chronic kidney disease epidemiology collaboration equation accuracy in predicting peritoneal dialysis-delivered creatinine clearance

INTRODUCTION

Measuring total (residual kidney plus peritoneal) creatinine clearance (CrCl) with 24-h urine and dialysate collections is recommended for peritoneal dialysis (PD) adequacy evaluation. Prediction equations applied in this instance could simplify the approach. Cockcroft-Gault and modification of diet in renal disease (MDRD) four (MDRD-4) and six (MDRD-6) variables equations have been tested in this setting, and conflicting results have been reported. The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is currently considered to be more sensitive than the established equations for kidney function estimation. However, its performance in PD adequacy evaluation has not been studied. Our aim was to assess CKD-EPI equation's performance in predicting total measured CrCl (MCC) in PD patients.

MATERIAL AND METHODS

A group of 23 consecutive PD patients, male/female: 5/18, median age: 66 (32-91) years, median time on PD 32 (2-126) months, were enrolled in the study. All were treated by automated PD (APD). Sixteen out of twenty-three had residual renal function (RRF). MCC was determined from 24-h dialysate and urine collections and also predicted by Cockcroft-Gault, MDRD (4 and 6), and CKD-EPI equations.

RESULTS

CKD-EPI and MDRD-6 estimation results were similar to MCC (9.01 ± 3.90 and 9.54 ± 2.98 vs. 8.64 ± 3.75 mL/min/1.73 m(2) p = 0.49 and 0.09, respectively). Neither the presence nor the volume of residual urine affected the accuracy of prediction. Cockcroft-Gault and MDRD-4 equations differed significantly from MCC and were not accurately predictive.

CONCLUSION

CKD-EPI equation could be used with accuracy for predicting MCC in PD patients. Only MDRD-6 showed similar accuracy, whereas MDRD-4 and Cockcroft-Gault equations were found to be inappropriate in this setting.

Comparison of glomerular filtration rate estimated by plasma clearance method with modification of diet in renal disease prediction equation and Gates method

Glomerular filtration rate (GFR) prediction equations are widely used in clinical practice for quick assessment of kidney function. Gates method using radionuclide technique is an alternative to prediction equations for quick assessment of GFR. Aim of the study was to compare Gates method and modification of diet in renal disease (MDRD) equation in a sizeable patient population with wide range of renal function to evaluate their clinical utility. GFR was estimated in 897 subjects with wide range of renal function by gates method, and MDRD equation and results were compared against measured GFR. Subjects were divided in to 4 groups (0-30 ml, 31-60 ml, 61-90 ml, >90 ml) on the basis of measured GFR and comparison between two methods done through linear regression analysis. Analysis of R² indicated that 56% of the interindividual variability for Gates GFR was in accordance to variation in measured GFR, in the GFR range of (0-30 ml), this value dropped to 39% in the GFR range of 31-60 ml, 40% in the GFR range of 61-90 ml, 26.4% in the GFR range of >90 ml, the corresponding figure for MDRD GFR were 47.9%, 31.1%, 17.6% and 16.1%, respectively. Gates method is more precise for GFR estimation at all levels of renal function.

Assessing creatinine clearance from modification of diet in renal disease study equations in the ADEMEX cohort: limitations and potential applications

BACKGROUND AND OBJECTIVES

Twenty-four-hour urine and dialysate collections provide accepted means to assess adequacy in peritoneal dialysis (PD). Recent publications suggest that creatinine clearance (CrCl) estimated from the Modification of Diet in Renal Disease (MDRD) equations (eCrCl) accurately approximates measured CrCl (mCrCl) derived from 24-hour collections of urine and dialysate and might serve as an alternative means to assess small-solute clearance and adequacy in PD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Post hoc analysis of data from patients enrolled in ADEMEX was used to assess agreement between mCrCl and eCrCl derived by four- and six-variable MDRD equations (4V-MDRDE and 6V-MDRDE, respectively). Additionally, associations among mCrCl, eCrCl, and survival were determined.

RESULTS

Acceptable precision was observed between mCrCl and 4V-MDRDE-eCrCl and 6V-MDRDE-eCrCl for the entire cohort. Precision was markedly diminished when analysis was limited to functionally anuric patients with mCrCl < 12 ml/min per 1.73 m². Although there was no association between survival and mCrCl, for every 1-ml/min per 1.73 m² increase in 4V- and 6V-MDRDE-eCrCl, there was a 6% and 4% increase in risk of death, respectively. There was a negative association between MDRDE-eCrCl and creatinine appearance rates, suggesting MDRDE-eCrCl is significantly confounded by individual differences in muscle mass.

CONCLUSIONS

MDRDE-eCrCl provides demographically comparable values to 24-hour urine and dialysate collections across the ADEMEX cohort. However, MDRDEs should not be used to assess small-solute removal or adequacy in individual PD patients or to predict outcome in any cohort of patients over narrow ranges of limited clearance.