Mechanical Aspects of Dialysis: A Recommended Technique for Obtaining the Post-Dialysis BUN

Pharmacokinetic Properties of Dapagliflozin in Hemodialysis and Peritoneal Dialysis Patients

BACKGROUND

Sodium-glucose cotransporter 2 (SGLT2) inhibitors attenuate incident cardiovascular outcomes, irrespective of baseline GFR, in conservatively managed CKD. As this condition inexorably progresses to demanding KRT, drug withdrawal is supported by the current lack of evidence of safety of SGLT2 inhibitors in dialysis.

METHODS

This study was a prospective, single-center, open-label trial ( ClinicalTrials.gov identifier: NCT05343078 ) aimed at assessing the pharmacokinetic properties and safety of dapagliflozin in patients with kidney failure on regular dialysis regimens compared with those with type 2 diabetes and age- and sex-matched controls with normal kidney function. Peripheral blood samples were collected from both groups every 30 minutes for 4 hours and again after 48 hours after ingestion of dapagliflozin 10 mg, which occurred immediately before dialysis session initiation in the kidney failure group. This protocol occurred in drug-naïve patients and again after six daily doses of dapagliflozin to assess whether the drug had accumulated. The plasma and dialysate levels of dapagliflozin at each time point were determined by liquid chromatography and used to calculate pharmacokinetics parameters (peak concentration [C max ] and area under the plasma concentration-versus-time curve) for each participant.

RESULTS

Dapagliflozin C max was 117 and 97.6 ng/ml in the kidney failure and control groups, respectively, whereas the corresponding accumulation ratios were 26.7% and 9.5%. No serious adverse events were reported for either group. Dapagliflozin recovered from dialysate corresponded to 0.10% of the administered dose.

CONCLUSIONS

In patients with kidney failure on dialysis, dapagliflozin was well tolerated, was slightly dialyzable, and had nonaccumulating pharmacokinetic properties.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Pharmacokinetics and Dialyzability of Dapagliflozin in Dialysis Patients (DARE-ESKD 1), NCT05343078.

Haemodialysis Access: A Single Centre UK Experience

Background

The aim of this study was to determine whether the US National Kidney Foundation Disease Outcome Quality Initiative (K/DOQI) guidelines on haemodialysis access could be achieved and to examine its relevance to patients on dialysis in the UK.

Method

A cross sectional study of chronic haemodialysis patients at our institution which involved case note review and measurements of biochemical parameters and dynamic venous pressure (dVP) was performed. Patients with polytetrafluoroethylene (PTFE) grafts were followed prospectively for 18 months.

Results

262 patients were studied - 12%, 43%, 30% and 15% underwent dialysis through dialysis catheters, radial-cephalic fistulae (rAVF), brachial-cephalic fistulae (bAVF) and PTFE grafts respectively. RAVFs, bAVFs and PTFE grafts were the primary access (i.e. the first access created for the patient) in 58%, 35% and 7% respectively. Compared with patients of Caucasian origin, patients of Afro-Caribbean race were 3.80 times (95% confidence limit: 1.51 – 9.53) more likely to have a PTFE graft. Patients with higher “dry weights” were more likely to have PTFE grafts (p<0.005 by ANOVA). Dialysis adequacy was similar irrespective of type and site of access. We found that 64% of PTFE grafts, 46% of bAVFs and 13% of rAVF had dVPs greater than 150 mmHg, (p<0.0001 by χ2). This threshold recommended by DOQI predicted 12 of 13 dysfunctional grafts, but had a positive predictive value of only 50%.

Conclusion

We have demonstrated that the K/DOQI guidelines are not only achievable, but that they can be exceeded by a considerable margin. Our data also suggest that the demographic details of patients within a unit will influence the achievable proportion of AVF: PTFE grafts (the proportion of PTFE grafts in Afro-Caribbeans being 3 times higher than in Whites). Although a dVP >150 mmHg proved sensitive in predicting future graft dysfunction, it had low specificity.

Sleep quality, daytime sleepiness and health-related quality-of-life in maintenance haemodialysis patients

Objectives

To assess the relationship between sleep quality, daytime sleepiness and health-related quality-of-life (HRQoL) in Chinese patients undergoing maintenance haemodialysis (MHD).

Methods

This cross-sectional study enrolled patients undergoing MHD. Self-reported sleep quality (Pittsburgh Sleep Quality Index [PSQI]), daytime sleepiness (Epworth Sleepiness Scale [ESS]) and HRQoL (36-item Short Form [SF-36]) were recorded for all patients.

Results

Sixty eight patients (mean ± SD age = 61.75 ± 16.56 years; 43 male/25 female) who regularly received MHD were included. The prevalence of poor sleepers was 69.1% (47/68) and daytime sleepiness was 11.8% (eight of 68). Poor sleepers had a significantly lower Physical Component Scale (PCS) score, Mental Component Scale (MCS) score and total SF-36 score than good sleepers. The PSQI score correlated inversely with both the PCS and MCS scores and correlated positively with age. Independent variables associated with total SF-36 score were duration of MHD, ESS score and PSQI score.

Conclusions

Poor sleep quality is a common and severe issue for MHD patients in east China. Both sleep quality and daytime sleepiness were associated with lower HRQoL scores.

Determination of urea distribution volume for Kt/V assessed by conductivity monitoring

BACKGROUND

Kt/V can be calculated continuously during dialysis without blood samples using the ionic dialysance method. Unlike the usual method using blood samples, a precise value for the patients' urea distribution volume is required. This study compared different methods for the determination of urea distribution volume (V) to evaluate their use in Kt/V measurement, based on conductivity monitoring.

METHODS

Ten patients were studied during 40 dialysis sessions. Total body water and V were determined using bioimpedance spectroscopy (BIS), anthropometric data, and blood-based kinetic data. Ionic dialysance was measured by conductivity monitoring.

RESULTS

Total body water measured by bioimpedance was determined as VBIS= 37.0 +/- 7.1 L or 49.6 +/- 4.4% of body weight. V determined using ionic dialysance as input to urea kinetic modeling (UKM) was found to correlate well with total body water (VKecn= 36.4 +/- 5.2 L). All anthropometric equations overestimated measured V: VWatson= 40.7 +/- 3.9 L, VHume= 41.8 +/- 2.5 L, VChertow= 44.6 +/- 3.3 L, and VChumlea= 43.1 +/- 2.9 L. Single-pool Kt/V obtained by kinetic modeling was used as reference (Kt/V)SPVV= 1.49 +/- 0.15. Using different Vs as the V component in the ionic dialysance Kt/V, we obtained: Kecn*t/VWatson= 1.34 +/- 0.12, Kecn*t/VBIS= 1.51 +/- 0.21 and Kecn*t/VKecn= 1.52 +/- 0.18.

CONCLUSION

The single-pool Kt/V calculated using the ionic dialysance method agreed with the conventional blood sample method provided that V was calculated using BIS or urea kinetics. V by either method was reproducible and varied little in an individual patient. Monthly determination of V allows determination of Kt/V for each dialysis session by ionic dialysance.

Effect of high-flux dialysis on the anaemia of haemodialysis patients

BACKGROUND

Anaemia is one of the major clinical characteristics of patients with chronic renal failure, and has a considerable effect on morbidity and mortality. Adequate dialysis is of paramount importance in correcting anaemia by removing small and medium-sized molecules, which may inhibit erythropoiesis. However, high-molecular-weight inhibitors cleared only by means of highly porous membranes have also been found in uraemic serum and it has been claimed from uncontrolled studies that high-flux dialysis could improve anaemia in haemodialysis patients.

METHODS

We therefore planned this multicentre randomized controlled trial with the aim of testing whether the use of a large-pore biocompatible membrane for a fixed 12-week follow-up improves anaemia in haemodialysis patients in comparison with the use of a conventional cellulose membrane. Eighty-four (5.3%) of a total of 1576 adult haemodialysed patients attending 13 Dialysis Units fulfilled the entry criteria and were randomly assigned to the experimental treatment (42 patients) or conventional treatment (42 patients).

RESULTS

Haemoglobin levels increased non-significantly from 9.5+/-0.8 to 9.8+/-1.3 g/dl (dP=0. 069) in the population as a whole, with no significant difference between the two groups (P:=0.485). Erythropoietin therapy was given to 32/39 patients (82%) in the conventional group, and 26/35 (74%) in the experimental group (P:=0.783) with subcutaneous administration to 26/32 patients in conventional and to 23/26 patients in experimental group, P:=0.495. Dialysis dose (Kt/V) remained constant in both groups (from 1.30+/-0.17 to 1.33+/-0.20 in the conventional group and from 1.28+/-0.26 to 1.26+/-0.21 in the experimental group, P:=0.242). Median pre- and post-dialysis beta(2)-microglobulin levels remained constant in the conventional group (31.9 and 34.1 mg/dl at baseline) and decreased in the experimental group (pre-dialysis values from 31.1 to 24.7 mg/dl, P:=0.004 and post-dialysis values from 24.8 to 20.8 mg/dl, P:=0.002). Median erythropoietin doses were not different at baseline (70 IU/kg/week in conventional treatment and 90 IU/kg/week in experimental treatment, P:=0.628) and remained constant during follow-up (from 70 to 69 IU/kg/week in the conventional group and from 90 to 91 IU/kg/week in the experimental group, P:=0.410). Median erythropoietin plasma levels were in the normal range and remained constant (from 12.1 to 12.9 mU/ml in the conventional group and from 13.2 to 14.0 mU/ml in the experimental group, P:=0.550).

CONCLUSIONS

This study showed no difference in haemoglobin level increase between patients treated for 3 months with a high-flux biocompatible membrane in comparison with those treated with a standard membrane. When patients are highly selected, adequately dialysed, and have no iron or vitamin depletion, the effect of a high-flux membrane is much less than might be expected from the results of uncontrolled studies.

A new method of post-dialysis blood urea sampling: the 'stop dialysate flow' method

BACKGROUND

A standardized practical method of post-dialysis blood sampling is required to improve the precision of using urea kinetics in the evaluation of haemodialysis dose and to permit comparative audit. The methods recommended in the Renal Association and Dialysis Outcomes Quality Initiative (DOQI) guidelines reduce the blood pump speed to a low rate at the end of haemodialysis before blood sampling after 10 and 15 s respectively. However, these 'low flow' methods compensate only partially for cardiopulmonary recirculation and may be impractical in routine practice because they involve sequential steps and require accurate timing of sampling. Therefore we have evaluated an alternative method of stopping only the dialysate flow at the end of the haemodialysis session before performing post-dialysis blood sampling.

METHODS

The study was performed in three phases. Serial measurements of blood urea were obtained from arterial and venous samples taken at times 0, 30, 60, 120, 180, 240, 300 and 360 s after stopping dialysate flow and leaving the extracorporeal blood flow rate unchanged at the end of the haemodialysis session in 10 patients. A peripheral venous sample was also taken from the contralateral arm at 0 s to reflect body water urea concentration at the end of dialysis without the effect of access recirculation and with a minimal effect of cardiopulmonary recirculation. The same haemodialysis prescription was repeated in the same 10 patients using the Renal Association method to permit comparison between the two methods. The practical use of the 'stop dialysate flow' method was then evaluated in 117 regular haemodialysis patients undergoing routine monthly assessment of dialysis adequacy and compared with sampling immediately post-dialysis.

RESULTS

Within 4 min of stopping the dialysate flow there was no difference between the blood urea concentrations of arterial and venous samples, indicating cessation of diffusion across the dialysis membrane. Also the blood urea concentrations in all of the arterial and venous samples between 4 and 6 min were constant and were equivalent to the blood urea concentration of the peripheral venous sample taken at 0 s. These data suggest that post-dialysis blood sampling may be performed 5 min after stopping dialysate flow at the end of the haemodialysis session. In contrast, the blood urea concentration in the post-dialysis samples obtained using the Renal Association method were lower than the contralateral arm blood urea concentration taken at 0 s (0.31+/-0.42; P<0.05) and consequently the percentage URR was higher (1.35+/-1.84%). In 117 patients the post-dialysis blood urea sample 5 min after stopping dialysate flow averaged 5.49+/-2.11 mmol/1 compared with 5.07+/-2.05 mmol/l immediately after the end of the haemodialysis session (P<0. 0001). This was equivalent to a reduction in URR from 71.7+/-8.3% with sampling immediately post-dialysis to 69.1+/-9.3% with the 'stop dialysate flow' method.

CONCLUSIONS

This study shows that there is a window period between 4 and 6 min after stopping dialysate flow at the end of the haemodialysis session when the blood urea concentration in a sample taken from any part of the extracorporeal circuit remains constantly within the co-efficient of variation of laboratory measurement, and is equivalent to a peripheral venous sample taken immediately at the end of the dialysis session. A 'stop dialysate flow' method with blood sampling after 5 min offers several advantages over 'slow flow' methods, since it allows for cardiopulmonary as well as access recirculation, does not require precise timing of blood sampling, and is simple to perform in a busy renal unit. For these reasons the 'stop dialysate flow' method may be used for routine monitoring of the adequacy of delivered haemodialysis and for comparative audit among haemodialysis centres.

Improved urea reduction ratio and Kt/V in large hemodialysis patients using two dialyzers in parallel

Delivered dose of hemodialysis (HD) in large patients with end-stage renal disease is often less than adequate. Fourteen chronic HD patients with weights greater than 80 kg participated in a prospective, cross-over study comparing urea reduction ratio (URR +/- SEM) and the fractional clearance index for urea (eKt/V(urea) +/- SEM) on a single polysulfone dialyzer for a control (HDC) period of 4 weeks versus clearances obtained with two dialyzers in parallel during an intervention (HDP) period of 4 weeks. Clearance of the surrogate middle molecule iohexol (C(Io)) was also measured. Health status was assessed with the SF-36. Blood and dialysate flow rates and duration of HD sessions were constant. URR increased from 0.67 +/- 0.006 during HDC to 0.72 +/- 0.006 with HDP (P < 0.0001). eKt/V(urea) increased from 1.16 +/- 0.021 to 1.34 +/- 0.021 (P < 0.0001). Increased URR and eKt/V(urea) occurred in all 14 during HDP (P < 0.05). C(Io) during HDP averaged 182 +/- 7.7 mL/min compared with 131 +/- 5.4 mL/min in HDC sessions (P < 0.00001). Health status improved in six of eight categories. Expense increased approximately $14.27 per dialysis with HDP. In 11 of 14 patients continued on two dialyzers in parallel for 1 year, monthly eKt/V averaged 1.46 +/- 0.066, and health status further improved in five of eight categories. In large patients, two dialyzers in parallel increased urea and iohexol clearance. Increased urea clearance was maintained for 1 year, and health status improved.