Comparisons of Kt/V evaluated using an online method and calculated from urea measurements in patients on intermittent hemodialysis

Kt/V(urea) (Kt/V) depends on the method applied for its evaluation. Our aim was to compare Kt/V obtained using the conductivity online method and that calculated from urea measurements. Studies were carried out in 40 patients. A stable dialysis schedule was maintained during the study. Online Kt/V was measured every week or 4 consecutive months. Single pool Kt/V (spKt/V) was calculated from urea estimations in the fourth week of the first month and in the last week of the fourth month of studies, using the formulas: (1)spKt/V = -ln(Ct/Co), where Ct is the postdialysis urea concentration obtained at the end of dialysis, Co the predialysis urea concentration obtained before the start of the blood pump; (2)spKt/V = -ln(R - 0.008 x t - f x UF/W), where R is the Ct/Co, t the duration of HD session, f=1.0, UF is the ultrafiltration volume (l), W is the body weight after the HD session; and (3)spKt/V + -ln(R - 0.008 x t) + (4 - 3.5 x R) x UF/W. The equilibrated Kt/V (eKt/V) was calculated as (3)spKt/V - {0.47 x [(3)spKt/V]/t} + 0.02. Correlation analysis was performed between all obtained Kt/V. Weekly online Kt/V was stable during 4 months of studies. In the first month, the respective values of online Kt/V, (1)spKt/V, (2)spKt/V, (3)spKt/V, and eKt/V were 1.15+/-0.14, 1.16+/-0.14, 1.38+/-0.17, 1.36+/-0.20, and 1.22+/-0.13. In the fourth month, these values were 1.17+/-0.14, 1.16+/-0.17, 1.38+/-0.22, 1.35+/-0.20, and 1.22+/-0.18. The respective values of Kt/V, estimated in the first and fourth month, were not different and showed a positive correlation: the highest one occurred between online Kt/V estimated at the indicated study periods (r=0.713, p=0.0000). Online Kt/V was significantly lower than (2)spKt/V, (3)spKt/V, and eKt/V. Correlation coefficients between online Kt/V, spKt/V, and urea reduction ratio did not exceed 0.490. Our studies show that Kt/V obtained using online monitoring indicates a lower intermittent hemodialysis adequacy that those calculated from urea measurements. This difference has to be remembered in application of results to clinical practice.     

Daily Hemodialysis versus Standard Hemodialysis: TAC,TAD, Weekly eKt/V,std(Kt/V), and PCRn

Seven patients, mean age 42.57 ± 15.69 years (range 21 – 67 years), on standard hemodialysis (SHD), 4 – 5 hours, three times per week for 11.0 ± 6.63 years (range 1 – 18 years), were switched to daily hemodialysis (DHD), 2 – 2.5 hours, six times per week. For each type of treatment similar parameters were applied, and the total weekly time was the same. Mean duration of DHD was 15.4 ± 4.98 months (range 7 – 20 months). We report here our results of quantification in each method, including time-averaged concentration (TAC), normalized protein catabolic rate (PCRn), equilibrated Kt/V (eKt/V), equivalent normalized continuous standard clearance [std(Kt/V)], equivalent renal urea clearance (eKRn), and time-averaged deviation (TAD). With DHD, urea TAC was reduced from 19.09 ± 3.47 to 15.16 ± 3.21 mmol/L (p = 0.026), urea TAD diminished from 4.76 ± 1.04 to 2.52 ± 0.57 mmol/L (p = 0.000 53), PCRn increased from 1.11 ± 0.23 to 1.42 ± 0.24 g/kg/day (p = 0.001), weekly eKt/V increased from 4.11 ± 0.31 to 4.74 ± 0.43 (p = 0.000 25), std(Kt/V) rose from 2.17 ± 0.06 to 4.02 ± 0.25 (p = 0.0001), and eKRn increased from 12.96 ± 0.60 to 21.7 ± 3.09 mL/min (p = 0.000 45). On DHD the most important quantitative variation is the decrease of urea TAD (closer to that of a healthy kidney), due to the increased frequency of dialysis; std(Kt/V) practically doubled and represents 30% of that of normal renal function. These changes are probably the main explanation for the clinical improvements, but it is difficult to dissociate the effects of increased dialysis dose from the effects of decreased TAD.     

Gender,low Kt/V,and mortality in Japanese hemodialysis patients: Opportunities for improvement through modifiable practices

Guidelines have recommended single pool Kt/V > 1.2 as the minimum dose for chronic hemodialysis (HD) patients on thrice weekly HD. The Dialysis Outcomes and Practice Patterns Study (DOPPS) has shown that “low Kt/V” (<1.2) is more prevalent in Japan than many other countries, though survival is longer in Japan. We examined trends in low Kt/V, dialysis practices associated with low Kt/V, and associations between Kt/V and mortality overall and by gender in Japanese dialysis patients. We analyzed 5784 HD patients from Japan DOPPS (1999–2011), restricted to patients dialyzing for >1 year and receiving thrice weekly dialysis. Logistic regression models estimated the relationships of patient characteristics with Kt/V. Logistic models also were used to estimate the proportion of low Kt/V cases attributable to various treatment practices. Multivariable Cox regression was used to estimate the associations of low Kt/V, blood flow rate (BFR), and treatment time (TT), with all‐cause mortality. From 1999 to 2009, the prevalence of low Kt/V declined in men (37–27%) and women (15–10%). BFR <200 mL/min, TT <240 minutes, and dialyzate flow rate (DFR) < 500 mL/min were common (35, 13, and 19% of patients, respectively) and strongly associated with low Kt/V. Fifteen percent of low Kt/V cases were attributable to BFR <200 and 13% to TT <240, compared to only 3% for DFR <500. Lower Kt/V was associated with elevated mortality, more so among women (hazard ratio [HR] = 1.13 per 0.1 lower Kt/V, 95% CI: 1.07–1.20) than among men (HR = 1.06 per 0.1 lower Kt/V, 95% CI: 1.00–1.12). The relatively large proportion of low Kt/V cases in Japanese facilities may potentially be reduced 30% by increasing BFR to 200 mL/min and TT to 4 hours thrice weekly in HD patients. Associations of low Kt/V with elevated mortality suggest that modification of these practices may further improve survival for Japanese HD patients.     

Nightly home hemodialysis: outcome and factors associated with survival

Nightly home hemodialysis (NHHD) has been reported to have a much better survival than the excessive mortality of thrice-weekly in-center dialysis, but the factors influencing survival of NHHD have not been investigated in detail. We studied the association of survival in a 12-year study of 87 NHHD patients from a single center evaluating demographic, sociologic, and anthropomorphic factors, diagnosis, comorbidity, vintage, and dialysis performance and efficiency. Secondly, we compared the survival of the 87 NHHD patients with that reported by the United States Renal Data System (USRDS) using standardized mortality rate (SMR). The average patient age was 52 ± 15 years, and 59% were males, 51% African Americans, and 25% had diabetes. The patients dialyzed 40 ± 6 hours weekly with a stdKt/V of 5.25 ± 0.84. Thirteen patients died. The cumulative survival was 79% at 5 years and 64% at 10 years. Using Cox proportional hazards univariate analysis, 7 of 26 factors studied were associated with mortality: less than high school education, hour of each dialysis, comorbidities, secondary renal disease, congestive heart failure, Leypoldt's eKt/V, and Daugirdas Kt/V. In backward stepwise Cox analysis, education and hour of dialysis were the only factors independently associated with survival. The standardized mortality rate was only 0.30 of that reported by the United States Renal Data System for patients on thrice-weekly hemodialysis adjusted for age, gender, race, and diagnosis. The influence of education was the most significantly associated with survival, and the duration of each dialysis treatment was important. The survival rate of NHHD patients appeared to be superior to intermittent hemodialysis.     

Length of Dialysis Session Is More Important Than Large Kt/V in Hemodialysis

Long, slow hemodialysis (3 × 8 hours/week) has been used without significant modification in Tassin, France, for 30 years with excellent morbidity and mortality rates. A long dialysis session easily provides high Kt/V_urea and allows for good control of nutrition and correction of anemia with a limited need for erythropoietin (EPO). Control of serum phosphate and potassium is usually achieved with low-dose medication. The good survival achieved by long hemodialysis sessions is essentially due to lower cardiovascular morbidity and mortality than in short dialysis sessions. This, in turn, is mainly explained by good blood pressure (BP) control without the need for antihypertensive medication. Normotension in this setting is due to the gentle but powerful ultrafiltration provided by the long sessions, associated with a low salt diet and moderate interdialytic weight gains. These allow for adequate control of extracellular volume (dry weight) in most patients without important intradialytic morbidity. Therefore, increasing the length of the dialysis session seems to be the best way of achieving satisfactory long-term clinical results.     

Dialysis adequacy and nutritional status of hemodialysis patients

To characterize the nutritional status of renal failure patients and its relationship with hemodialysis adequacy measured by Kt/V, a study was carried out with a population of 44 adult patients with renal failure and mean age 51+/-15 years. Anthropometric data, such as dry weight, height, arm circumference, triceps skinfold thickness, mid-arm muscle circumference, and body mass index were assessed, and biochemical tests were conducted for urea, potassium, creatinine, serum albumin, and phosphorus levels, in addition to hemogram and quarterly urea reduction rate average (Kt/V). In order to evaluate calorie intake, a dietary questionnaire on habitual daily food ingestion was administered, taking into consideration the hemodialysis date. The patients were divided into 2 separate groups for the statistical analysis, with 50% of the patients in each group: A (Kt/V<1.2) and B (Kt/V>1.2). The data were tabulated as mean and standard deviation, with differences tested by Student's t test. The correlations between variables were established by the coefficient p of Pearson. Most of the patients (43%) were considered eutrophic, based on the BMI, and presented inadequate calorie intake, corresponding to 88.5+/-24% (30.8 kcal/kg actual weight) of the total energy required and adequate protein intake, reaching 109.9+/-40% of the recommended daily allowance (1.24 g/kg of actual weight). There was a correlation of Kt/V with anthropometric parameters such as body mass index, arm circumference, and mid-arm muscle circumference. The biochemical parameters related to dialysis adequacy were albumin, ferritin, and urea (predialysis). Well-dialyzed patients presented better levels of serum albumin. There was an influence of gender and age on correlations of the analyzed variables. Female and younger patients presented better dialysis adequacy. The dialysis adequacy was related to the nutritional status and influenced by the protein intake and body composition. Gender and age had an important influence in the dialysis adequacy, as men presented lower dialysis adequacy and younger adults presented better dialysis adequacy. Further research is necessary to understand better how to facilitate effective and efficient techniques for the nutritional status assessment of hemodialysis patients.     

Catheter‐related bacteremia and mortality in frequent nocturnal home hemodialysis

Frequent nightly home hemodialysis (NHHD) has emerged as an attractive alternative to thrice weekly in‐center hemodialysis, albeit with preponderant long‐term hemodialysis catheter used. Sixty‐three NHHD patients from University of Virginia Lynchburg Dialysis Facility were matched 1:2 with 121 conventional hemodialysis patients admitted to Fresenius Medical Care North America facilities from January 1, 2007 to December 31, 2010. Matching considered age (± 5 years), gender, race, dialysis vintage, and diabetes. The primary end‐point was the combined incidence of bacteremia/sepsis, for up to 20 months or upon changing to a fistula/graft (with catheter removal), transferring to peritoneal dialysis (PD), or at the time of kidney transplant or death. No significant differences were observed in rate of fistula/graft conversion, transfer to PD, transplant, or death between NHHD and in‐center hemodialysis (IHD) groups. For the first catheter used, the rate of catheter‐related sepsis was not significantly different between the NHHD (1.77 per 100 patient months) and IHD (2.03 per 100 patient months; P = 0.21). Combining all catheters, the rate of bacteremia/sepsis per 100 patient months in the NHHD group was 1.51 and in the IHD group was 2.01 (P = 0.35). Median catheter lifespan for the first catheter was 5.6 (1.7～19.0) for NHHD and 4.6 (2.7～7.8) for the IHD group (P = 0.64), and for all catheters used was 5.2 (Q1～Q3 = 1.5～15.2) months in NHHD group, and 4.1 (2.0～6.8) months in IHD group (P = 0.20). The rate of bacteremia and death is not different for up to 20 months in catheter users who dialyze via frequent NHHD vs. thrice weekly IHD.     

Inadvertently high dialysate magnesium causing weakness and nausea in hemodialysis patients

As maintenance hemodialysis patients are exposed to large quantities of dialysis water, any contamination of it might be reflected in plasma levels. We present a series of cases due to such a contamination. Six maintenance hemodialysis patients dialyzing at the same peripheral hemodialysis facility presented to us over a short period of time with symptoms mimicking inadequate dialysis. Their blood urea and creatinine levels were not very high, but all the patients had hypermagnesemia [serum Mg levels = 1.8 (±0.3) mmol/L]. Except for one patient who had cardiac arrest at presentation, all patients improved after undergoing hemodialysis at our center [serum Mg at discharge = 0.86 (±0.01) mmol/L]. The origin of hypermagnesemia was traced to dialysis water contamination with magnesium due to inadequate maintenance of the water treatment system. Corrective measures improved the quality of water, and no further cases were reported from that center. Proper maintenance and periodic checks of the quality of water are central to the outcomes of maintenance hemodialysis patients.     

Alirocumab in a high cardiovascular risk patient on hemodialysis with liver abnormalities

We present a male diabetic type 2 patient on hemodialysis (HD) with high cardiovascular (CVD) risk and hyperlipidemia. The patient was under cholesterol‐lowering therapy with statin and ezetimibe but he was obligated to discontinue due to chronic hepatitis C virus infection. Statins and ezetimibe may exert a potential hepatotoxic effect and for this reason, we attempted to find an alternative treatment to prevent CVD. Given that a potential hepatotoxic effect has not been reported for Abs SPCK9, we administered alirocumab 150 mg every 2 weeks for a total of 8 weeks. Low‐density lipoprotein levels have decreased and no side effects have been observed. In conclusion, alirocumab is a safe and efficient alternative therapy approach for HD patients with high CVD risk and liver abnormalities. We suggest that SPCK 9 inhibitors should be considered as a first line treatment for lowering cholesterol in this specific patient group.     

Remission of refractory Crohn's disease with anti-IL-12/23 therapy in a patient undergoing hemodialysis: A case report

Crohn's disease is a relapsing chronic inflammatory condition of the intestine with increasing prevalence around the world. Biologic therapies are currently widely used and have proved safe and effective in treating moderate to severe Crohn's disease. However, contemporary bibliography contains little information about the use of these drugs in patients with end-stage renal disease undergoing hemodialysis. Here we present a case of a 47-year-old female patient with treatment-refractory Crohn's disease on hemodialysis. In this patient, treatment with the anti-IL-12/23 receptor antibody ustekinumab was effective in inducing and maintaining remission while being safe in administering throughout hemodialysis.     

Right atrial thrombus in an asymptomatic hemodialysis patient with malfunctioning catheter and patent foramen ovale

The creation of an accurate functioning arteriovenous fistula has been a long-lasting problem in the hemodialysis setting. In spite of recent guidelines and largely because of the old age of the current dialysis population and a high incidence of diabetes mellitus, atherosclerosis, and related vascular problems, it is not always possible to create an adequate fistula. In that case, long-term tunneled indwelling central vein catheters are a frequently used alternative. Of the many possible complications related to venous access in hemodialysis patients, catheter dysfunction is the most prevalent. We report a 23-year-old female hemodialysis patient in whom such malfunctioning was followed by echocardiography that revealed a large right atrial thrombus (RAT) in close contact to the tip of a long-term indwelling catheter in the presence of a patent foramen ovale. Although RAT is a rare complication in hemodialysis patients, it has very specific therapeutic implications. The present patient underwent a successful surgical atrial thrombectomy. Our experience underscores that in cases of malfunctioning catheter, echocardiographic screening is mandatory.     

The growth of cracks in Ti–6Al–4V plate under combined high and low cycle fatigue

The fatigue crack growth rates in cross-rolled Ti–6Al–4V plate subjected to combined major and minor stress cycles have been measured at room temperature. The concept of crack closure was used to model the data for a test sequence using 1000 minor cycles per major cycle, and the model validated by either the accurate or safe prediction of the crack growth rates for a second series of tests involving 10,000 minor cycles per major cycle. Fatigue threshold values for the minor cycles derived from the growth rate data for combined major and minor cycle loadings were lower than those determined by the conventional load shedding method. In comparison with the behaviour of Ti–6Al–4V disc material which had been forged, the cross-rolled plate material exhibited: first, a clearly defined bilinear growth rate curve under a separate major cycle loading; second, similar or lower derived threshold values with separate minor cycle loadings; and third, reduced crack propagation lives for loadings combining major and minor cycles.     

Diffusion bonding of Al2O3-TiC composite ceramic and W18Cr4V high speed steel in vacuum

Al₂O₃-TiC composite ceramic and W18Cr4V high speed steel were joined by diffusion bonding with a Ti-Cu-Ti multi-interlayer in a vacuum of 10⁻⁴-10⁻⁵ Pa. The interfacial microstructures of the Al₂O₃-TiC/W18Cr4V joint were investigated with optical microscope and scanning electron microscopy. The elemental concentration near the diffusion interface was evaluated by electron probe microanalysis. The results indicate that an obvious transition zone was formed between Al₂O₃-TiC and W18Cr4V during the vacuum diffusion bonding. The elements in the transition zone are mainly Ti and Cu with a small amount of Fe. Element Ti concentrates near the two interfaces of the Al₂O₃-TiC/transition zone/W18Cr4V. The microhardness of the transition zone is lower than that of Al₂O₃-TiC and higher than that of W18Cr4V. The formation process of the transition zone consists of five stages: (i) Formation of Cu-Ti liquid phase; (ii) Full melt of Cu; (iii) Full melt of Ti; (iv) Formation of reaction layer; (v) Formation of Cu-Ti solid solution and increment of reaction layer.