Quotidian dialysis – update 2005

Cardiovascular Benefits of Extended-Time Nocturnal Hemodialysis

Hemodialysis (HD) remains the most utilized treatment for End-Stage Kidney Disease (ESKD) globally, mainly as conventional HD administered in 4 h sessions thrice weekly. Despite advances in HD delivery, patients with ESKD carry a heavy cardiovascular morbidity and mortality burden. This is associated with cardiac remodeling, left ventricular hypertrophy (LVH), myocardial stunning, hypertension, decreased heart rate variability, sleep apnea, coronary calcification and endothelial dysfunction. Therefore, intensive HD regimens closer to renal physiology were developed. They include longer, more frequent dialysis or both. Among them, Nocturnal Hemodialysis (NHD), carried out at night while asleep, provides efficient dialysis without excessive interference with daily activities. This regimen is closer to the physiology of the native kidneys. By providing increased clearance of small and middle molecular weight molecules, NHD can ameliorate uremic symptoms, control hyperphosphatemia and improve quality of life by allowing a liberal diet and free time during the day. Lastly, it improves reproductive biology leading to successful pregnancies. Conversion from conventional to NHD is followed by improved blood pressure control with fewer medications, regression of LVH, improved LV function, improved sleep apnea, and stabilization of coronary calcifications. These beneficial effects have been associated, among others, with better extracellular fluid volume control, improved endothelial- dependent vasodilation, decreased total peripheral resistance, decreased plasma norepinephrine levels and restoration of heart rate variability. Some of these effects represent improvements in outcomes used as surrogates of hard outcomes related to cardiovascular morbidity and mortality. In this review, we consider the cardiovascular effects of NHD.

The Use of Nocturnal Home Hemodialysis as Salvage Therapy for Patients Experiencing Peritoneal Dialysis Failure

Background

Failure of peritoneal dialysis (PD) results in poor quality of life and worsening morbidity in patients with end-stage renal disease (ESRD). Traditionally, hospital-based conventional hemodialysis has been the only option for this patient population. We hypothesized that nocturnal home hemodialysis (NHD), 3 – 6 sessions per week, 6 – 8 hours per session, is a suitable alternative salvage therapy for this vulnerable patient group.

Methods

This is a descriptive cohort study of all consecutive ESRD patients failing PD that were converted to NHD at the University Health Network and Humber River Regional Hospital from 2003 to 2005. Our primary objective was to describe the changes in clinical and biochemical indices before and after conversion from PD to NHD.

Results

69 patients required transfer from PD to another form of renal replacement therapy during the period of interest. Our pilot cohort included 8 ESRD patients (5 males, 3 females; age 53 ± 7 years). Mean duration on PD was 4.8 ± 4.6 years. NHD delivered a higher dose of dialysis, as reflected by lower plasma creatinine concentration 1 year after beginning NHD (from 1107 ± 312 μmol/L with PD to 649 ± 309 μmol/L, p = 0.01) and a rise in standardized Kt/V (from 2.21 ± 0.73 with PD to 4.49 ± 1.92 after 6 months of NHD, to 4.51 ± 1.77 after 1 year of NHD; p < 0.001). There was a progressive and sustained rise in plasma albumin after conversion to NHD (from 31 ± 4 g/L with PD to 36 ± 4 g/L after 6 months of NHD, to 39 ± 2 g/L after 1 year of NHD; p = 0.001). Hemoglobin concentrations increased (from 102 ± 13 to 125 ± 7 g/L, p = 0.03), while erythropoietin requirement tended to fall (from 17500 ± 8669 to 9197 ± 7573 U/week). Plasma phosphate fell (from 2.1 ± 0.6 to 1.1 ± 0.3 mmol/L, p = 0.01) despite a decrease in phosphate binder requirement. Blood pressure profile also tended to improve after conversion to NHD.

Conclusion

Nocturnal HD represents a promising, viable, alternative renal replacement therapy for patients experiencing PD failure. The clinical impact of transferring ESRD patients failing PD to NHD deserves further investigation.

Physiological monitoring and control in hemodialysis: state of the art and outlook

Medical devices for monitoring and feedback control of physiological parameters of the dialysis patient were introduced in the early 1990s. They have a wide range of applications, aiming at increasing the safety and ensuring the efficiency of the treatment, and at an improved restoration of physiological conditions, leading to an overall reduction in morbidity and mortality. Such devices include sensors for the measurement of temperature, optical parameters and sound speed in blood, and electrical characteristics of the human body, and other parameters. Essential for the development of these devices is a detailed understanding of the pathophysiological background of a therapeutical problem. There is still a large potential to introduce new devices for further therapy improvement and automation. Also, the size of the hemodialysis market appears attractive; however, a new product has to meet several specific requirements in order to also become commercially successful. This review describes the therapeutic and technical principles of several available devices, reports on concepts for possible future devices, and presents a short overview on the market environment.

Cardiac and vascular structure and function parameters do not improve with alternate nightly home hemodialysis: an interventional cohort study

BACKGROUND

Nightly extended hours hemodialysis may improve left ventricular hypertrophy and function and endothelial function but presents problems of sustainability and increased cost. The effect of alternate nightly home hemodialysis (NHD) on cardiovascular structure and function is not known.

METHODS

Sixty-three patients on standard hemodialysis (SHD: 3.5-6 hours/session, 3-5 sessions weekly) converted to NHD (6-10 hours/session overnight for 3-5 sessions weekly). 2Dimensional transthoracic echocardiography and ultrasound measures of brachial artery reactivity (BAR), carotid intima-media thickness (CIMT), total arterial compliance (TAC) and augmentation index (AIX) were performed post dialysis at baseline and 18-24 months following conversion to NHD. In 37 patients, indices of oxidative stress: plasma malonyldialdehyde (MDA) and anti-oxidant enzymes: catalase (CAT), glutathione peroxidase (GPX) and superoxide dismutase (SOD) activity and total antioxidant status (TAS) were measured at baseline, 3 and 6 months.

RESULTS

Left ventricular mass index (LVMI) remained stable. Despite significant derangement at baseline, there were no changes in diastolic function measures, CIMT, BAR and TAC. AIX increased. Conversion to NHD improved bone mineral metabolism parameters and blood pressure control. Interdialytic weight gains increased. No definite improvements in measures of oxidative stress were demonstrated.

CONCLUSIONS

Despite improvement in uremic toxin levels and some cardiovascular risk factors, conversion to an alternate nightly NHD regimen did not improve cardiovascular structure and function. Continuing suboptimal control of uremic toxins and interdialytic weight gains may be a possible explanation. This study adds to the increasing uncertainty about the nature of improvement in cardiovascular parameters with conversion to intensive hemodialysis regimens. Future randomized controlled trials will be important to determine whether increases in dialysis session duration, frequency or both are most beneficial for improving cardiovascular disease whilst minimizing costs and the impact of dialysis on quality of life.

Nocturnal hemodialysis: effects on solute clearance, quality of life, and patient survival

PURPOSE OF REVIEW

Conventional hemodialysis is often an incomplete treatment for uremia. People receiving hemodialysis often report a poor quality of life and suffer from an accelerated mortality rate. Nocturnal hemodialysis provides long treatments at night in the home or dialysis center. This review will examine how long nocturnal treatments have impact on the clearance of small and larger retention products, and how these treatments influence quality of life and survival.

RECENT FINDINGS

Nocturnal hemodialysis is more effective at clearing most small and middle molecule retention products, and has been associated with improvements in quality of life, especially in those domains related to the effects of kidney disease. Survival on nocturnal hemodialysis is higher than expected, and studies suggest that patients receiving nocturnal hemodialysis have a mortality rate that is about one third of what is seen in similar patients receiving conventional hemodialysis.

SUMMARY

Although impressive, it is difficult to be sure how much of the results of these studies is due to the duration and timing of dialysis and how much relates to patient level factors and residual confounding, and further research in this area is required.

The impact of extended-hours home hemodialysis and buttonhole cannulation technique on hospitalization rates for septic events related to dialysis access

Few studies adequately document adverse events in patients receiving long, slow, and overnight hemodialysis (NHD). Concerns about high rates of dialysis access complications have been raised. This is an observational cohort study comparing hospital admission rates for vascular access complications between alternate nightly NHD (n=63) and conventional hemodialysis (n=172) patients established on chronic hemodialysis for at least 3 months. Overall, hospital admission rates and hospital admission rates for cardiac and all infective events are also reported. The NHD cohort was younger and less likely to be female, diabetic, or have ischemic heart disease than the conventional hemodialysis cohort. When NHD and buttonhole cannulation technique were used simultaneously, there was a demonstrated increased risk of septic dialysis access events: incidence rate ratio 3.0 (95% confidence interval 1.04-8.66) (P=0.04). The majority of blood culture isolates in NHD patients were gram-positive organisms, particularly Staphylococcus aureus. Alternate nightly NHD did not significantly change total hospital admissions or hospital admissions for indications other than dialysis access complications, compared with conventional hemodialysis. Our data suggest that buttonhole cannulation technique should be used with caution in patients performing extended-hours hemodialysis as this combination appears to increase the risk of septic access complications. Randomized-controlled trials are needed to confirm these findings.

Silicon induces minimal thromboinflammatory response during 28-day intravascular implant testing

Microelectromechanical systems (MEMS) are used to machine miniaturized implantable medical devices. Our group has used MEMS technology to develop hemofiltration membranes for use in renal replacement therapy, which possess enhanced selectivity and permeability. The use of silicon in blood-contacting environments may be limited, however, due to contact activation of the coagulation cascade by silicon, which forms the surface oxides in atmospheric conditions. As well, the reports of long-term biocompatibility of blood- contacting silicon devices are lacking. The aims of this pilot study were as follows: 1) to develop a model for investigating the effects of intravascular implants and 2) to characterize the degree of thrombosis and tissue inflammation incited by prolonged implantation of silicon materials. Silicon implants with and without polyethylene glycol (PEG) coatings were surgically implanted transluminally through rat femoral veins. Gore-Tex and stainless steel implants served as controls. The implants were left in vivo for 4 weeks. All femoral veins remained patent. The veins associated with silicon implants exhibited rare thrombi and occasional mild perivascular inflammation. In contrast, Gore-Tex and stainless steel controls caused moderate vein thrombosis and provoked a moderate to marked cellular infiltrate. Under scanning electron microscopy, bare silicon implants were found to have significant adherent microthrombi, whereas PEG-treated implants showed no evidence of thrombi. PEG-treated silicon seems to be biocompatible and holds potential as an excellent material with which to construct an implantable, miniaturized hemofiltration membrane.

Vancomycin pharmacokinetics and pharmacodynamics during short daily hemodialysis

BACKGROUND AND OBJECTIVES

Short daily hemodialysis (SDHD) is an alternative to thrice-weekly HD because of its putative physiologic benefits. The purpose of this study was to investigate the effect of SDHD on the pharmacokinetics and pharmacodynamics of vancomycin.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Six noninfected adults who had anuria and were treated with SDHD were studied and received four dialysis sessions over 4 days. After completion of the first SDHD, each patient received vancomycin 15 mg/kg by intravenous infusion. Blood samples were collected over the ensuing 3 days during each subsequent inter- and intradialytic period. Pharmacokinetic parameters were determined. Serum concentration-time profiles were simulated for four vancomycin regimens with maintenance doses administered after every other SDHD. Area under the serum-concentration time curve (AUC) from 0 to 48 hours, 48 to 96 hours, and 96 to 144 hours were calculated, and Monte Carlo simulations were performed to determine the probability of target attainment at an AUC/minimum inhibitory concentration (MIC) ratio ≥800 for each 48-hour AUC at MICs ranging from 0.5 to 2.0 μg/ml.

RESULTS

Median (range) systemic clearance was 7.2 ml/min (5.3 to 10.0 ml/min), and dialytic clearance was 104 ml/min (94 to 106 ml/min). The steady-state volume of distribution was 55.4 L (34.8 to 77.2 L). At MICs ≤1 μg/ml, probability of target attainment was >90% for each 48-hour AUC when vancomycin was administered as a 20-mg/kg loading dose followed by 10 mg/kg after every other SDHD.

CONCLUSIONS

Vancomycin pharmacokinetic parameters in SDHD are consistent with data from thrice-weekly HD. A loading dose of 20 mg/kg followed by 10 mg/kg after every other SDHD provides adequate exposure for pathogens with MICs ≤1 μg/ml.

In-center nocturnal hemodialysis: another option in the management of chronic kidney disease

BACKGROUND AND OBJECTIVES

Some patients are not optimally treated by conventional in-center hemodialysis (HD) and are unable to perform home HD. We examined the effect of in-center thrice-weekly nocturnal HD (INHD) on patient outcomes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients who were not optimally treated on conventional HD were offered INHD. Thirty-nine patients' laboratory data and medication use were analyzed for the 12 mo before and after conversion to INHD until September 1, 2007. Quality of life on conventional HD and INHD was compared.

RESULTS

After conversion to INHD, median values for phosphorus decreased from 5.9 to 3.7 mg/dl (P < 0.01), alkaline phosphatase level increased from 84 to 161 U/L (P < 0.01), and percentage reduction in urea increased from 74 to 89% (P < 0.01). The mean number of antihypertensive drugs prescribed declined from 2.0 to 1.5 (P < 0.05) during the course of INHD, and the mean daily dosage of phosphate binders declined from 6.2 to 4.9 at study end (P < 0.05). There was a significant reduction in erythropoietin-stimulating agent use of 1992 U/wk (P < 0.01). There was no significant change in median hemoglobin, iron saturation, corrected calcium, or parathyroid hormone levels. Overall, quality of life, sleep, intradialytic cramps, appetite, and energy level all improved significantly on INHD.

CONCLUSIONS

INHD offers an effective form of HD for long-term dialysis patients who are unable to perform home HD.

High-Performance Silicon Nanopore Hemofiltration Membranes

Silicon micromachining provides the precise control of nanoscale features that can be fundamentally enabling for miniaturized, implantable medical devices. Concerns have been raised regarding blood biocompatibility of silicon-based materials and their application to hemodialysis and hemofiltration. A high-performance ultrathin hemofiltration membrane with monodisperse slit-shaped pores was fabricated using a sacrificial oxide technique and then surface-modified with poly(ethylene glycol) (PEG). Fluid and macromolecular transport matched model predictions well. Protein adsorption, fouling, and thrombosis were significantly inhibited by the PEG. The membrane retained hydraulic permeability and molecular selectivity during a 90 hour hemofiltration experiment with anticoagulated bovine whole blood. This is the first report of successful prolonged hemofiltration with a silicon nanopore membrane. The results demonstrate feasibility of renal replacement devices based on these membranes and materials.

Nocturnal hemodialysis does not improve overall measures of quality of life compared to conventional hemodialysis

We conducted a randomized controlled trial to compare the quality of life of 52 patients undergoing nocturnal hemodialysis and conventional hemodialysis. Quality of life was measured using a number of established methods including the Kidney Disease Quality of Life Short Form and the preference-based Euroqol EQ-5D questionnaire (whose scores varied from 0 to 1). The primary outcome was a change in the Euroqol EQ-5D index scores between baseline and 6 months. We performed additional analyses comparing change in quality of life from pre-randomization (when patients were unaware of treatment allocation) to 6 months. Other analyses considered the impact of nocturnal hemodialysis on four pre-selected Kidney Disease Quality of Life Short Form domains, and the longer term impact of nocturnal hemodialysis on quality of life. Compared with conventional hemodialysis, nocturnal hemodialysis increased Euroqol-EQ-5D index scores by 0.05, which was not significantly different from baseline. When six-month values were compared with pre-randomization values rather than baseline values, the between group difference was larger (0.12) though it was still not statistically significant (P=.06). Nocturnal hemodialysis was associated with clinically and statistically significant improvements in selected kidney-specific quality of life domains (P=.01 for effects of kidney disease; P=.02 for burden of kidney disease). Our primary quality of life analysis did not demonstrate a statistically significant change between nocturnal hemodialysis and conventional hemodialysis, though statistically significant and clinically important changes in some secondary kidney-disease- specific measures were observed.

Successful pregnancies on nocturnal home hemodialysis

BACKGROUND AND OBJECTIVES

Women of childbearing age on conventional hemodialysis (CHD) have decreased fertility when compared with the general population. Even in women who conceived, maternal morbidity and fetal mortality remained elevated. We hypothesized that nocturnal hemodialysis (NHD) (3 to 6 sessions per week, 6 to 8 h per treatment), by augmenting uremic clearance, leads to a more hospitable maternal environment and therefore superior outcomes in fertility and pregnancy compared with CHD.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

This is a descriptive cohort study of all female patients achieving pregnancy and delivering a live infant while on NHD at the University Health Network, St. Michael's Hospital, and Humber River Regional Hospital from 2001 to 2006 in Toronto, Canada. Our primary objective was to describe maternal and fetal outcomes in addition to the changes in biochemical parameters after conception in our cohort.

RESULTS

Our cohort included five patients (age range, 31 to 37 yr) who had seven pregnancies while on NHD and delivered six live infants. All had previously been on CHD, but none conceived during that time. In all patients, the amount of hemodialysis was increased (from a weekly mean of 36 +/- 10 to 48 +/- 5 h; P < 0.01) after pregnancy was diagnosed. Mean predialysis blood urea and mean arterial BP were maintained within normal physiological parameters. The mean gestational age of the cohort was 36.2 +/- 3 wk and the mean birth weight was 2417.5 +/- 657 g. The maternal and fetal complications observed in the cohort included intrauterine growth restriction or small for gestational age (n = 2), preterm delivery (<32 wk) (n = 1), and shortened cervix threatened labor (n = 1). Anemia was accentuated during pregnancy, and intravenous iron and erythropoietin requirements were increased. To maintain normal physiological indices for plasma phosphate, an augmented dialysate phosphate supplementation regimen was required.

CONCLUSIONS

NHD may allow for improved fertility. Delivering a live infant at a mature gestational age is feasible for patients on NHD. Our cohort tended to have fewer maternal and fetal complications compared with historical controls. Hemoglobin and phosphate levels must be monitored with treatment adjusted accordingly.

Switching from Three Times a Week to Short Daily Online Hemodiafiltration: Effects on Acid-Base Balance

Aims

This study examines the effect of a change from the standard 4–5 hours 3 times a week of online hemodiafiltration (OL-HDF) to 2–2.5 hours daily (6 times a week) OL-HDF, on acid-base balance, and attempts assess the modifications of acid-base parameters, ionic concentration, and electrical charges of albumin and phosphate available for diffusion and convection mechanisms across the membrane and subsequent infusion.

Methods

In 18 patients on online HDF, blood gas, electrolytes (Na, K, Cl), lactate, phosphate, albumin, apparent strong ion difference (SIDa), effective strong ion difference (SIDe), strong ion gap (SIG), anion gap (AG), and bicarbonate and pH time-averaged concentration (TAC) and time-averaged deviation (TAD) variables were evaluated at baseline, and 1, 3, 6, 9, and 12 months after patients were switched to daily OL-HDF. Additionally, in 12 patients, the same parameters measured simultaneously at dialyzer inlet, outlet, and after reinfusion were studied.

Results

Throughout the study, weekly single-pool Kt/V, equilibrated Kt/V, and TAC urea remained constant. However, standard Kt/V increased and TAD urea decreased on daily OL-HDF. There were no statistical differences during the time span of 12 months in pH, cations (Na, K), anions (Cl, HCO–3 AG, and lactate), or SIDa, SIDe, and SIG pre-HDF; while pH and HCO3– TAD decreased from 0.02 and 1.02 ± 0.74 mEq/L, to 0.01 and 0.64 ± 0.52 mEq/L, respectively (p<0.01). Net albumin charge and AG increased significantly at dialyzer outlet and decreased after reinfusion.

Conclusions

We did not observe changes in the acid-base balance in patients who switched from 3 times a week to short daily OL-HDF. The main benefit observed was a lower pH and bicarbonate TAD. This shows a better physiology for daily OL-HDF.

Development of continuous implantable renal replacement: past and future

Most of the 400,000+ patients in the United States with kidney failure depend on dialysis treatments in dedicated dialysis centers for 3 h to 5 h, usually 3 times a week, but they still suffer from accelerated cardiovascular disease and infections. Extended daily dialysis, for 6 to 8 hours every day, seems to be associated with better outcomes but would overwhelm the dialysis networks and severely limit patient activity. Technology to miniaturize and automate home dialysis will be necessary to offer extended daily dialysis to most dialysis patients. Miniaturization of existing hollow-fiber polymer membranes is constrained by requirements for high driving pressures for circulation and convective clearance. Recent advances in membrane technology based on microelectromechanical systems (MEMS) promise to enable the development of continuous implantable renal replacement therapy. Silicon nanoporous membranes with a highly monodisperse pore size distribution have been produced using protocols amenable to low-cost batch fabrication similar to those used to produce microelectronics. Hydraulic permeability of the flat-sheet membranes with critical pore sizes in the range of 8-100 nm has been measured to confirm that conventional fluid transport models are sufficiently accurate for predictive design for bulk liquid flow in an implantable hemofilter. Membrane biocompatibility was tested in vitro with human proximal tubule cells and revealed that silicon does not exhibit cytotoxicity, as evidenced by the formation of confluent cell layers with tight junctions and central cilia. Filtration characterization demonstrated that the nanoporous membranes exhibit size-dependent solute rejection in agreement with steric hindrance models. These advances in membrane technology are fundamentally enabling for a paradigm shift from an in-center to implantable dialysis system.