Oral intake during hemodialysis: Is there an association with intradialytic hypotension?

Oral intake (OI) of food and fluid has been associated with hypotension during hemodialysis (HD). Trials evaluating this relationship are small. The objective of this study was to quantify OI and to examine its association with hypotension during HD. This is a cross-sectional retrospective chart review study of 3 consecutive HD runs (dialysate iCa=1.25 mmol/L) in 126 stable HD patients (n=378). For each run, the calculation for OI=total ultrafiltration-(net weight loss+IV fluids given). Hypotension was defined as a systolic blood pressure of <100 mmHg at any point during the run. The mean age of the patients was 60.9 years, 38.2% were female, 30.2% had diabetes mellitus, and the majority were Caucasian. The mean (SD) OI was 0.27 (0.352) L/run, range -1.061 to 1.901 L/run, with a normal distribution. In bivariate analysis, there was no correlation of OI with systolic blood pressure, diastolic blood pressure, or mean blood pressure (BP), and the mean OI did not differ among runs with hypotension (n=78) compared with uncomplicated runs (p=0.93). Oral intake was not predictive of hypotension in a multiple logistic regression model controlling for vintage, age, sex, BP medications, coronary disease, dialysis day and shift, diabetes mellitus, s-Ca, Na and ultrafiltration profiles, and dialysis temperature, even when the analysis was restricted to runs where the patients reached the prescribed dry weight within 0.1 kg. The results of this study suggest that the mean OI during dialysis is just over 0.25 kg, with some patients consuming several kilograms. The clinical significance of OI is uncertain. We did not find an association between OI and hypotension. It is likely that this association was confounded by failure to achieve the prescribed dry weight in a proportion of patients with a high OI, as well as interventions implemented in response to hypotension in previous runs. For example, patients with previous episodes of low BP are advised to limit OI, are prescribed profiles, and so on. There may be other deleterious effects of high OI including hypertension and cardiac disease. The generalizability of the results of this largely Caucasian study population is a recognized limitation. Further prospective and blinded studies are needed to examine the association between OI and hypotension, the long-term clinical consequences of OI, and to define thresholds for recommended OI during dialysis.     

Survival with short‐daily hemodialysis: Association of time,site, and dose of dialysis

In thrice‐weekly hemodialysis, survival correlates with the length of time (t) of each dialysis and the dose (Kt/V), and deaths occur most frequently on Mondays and Tuesdays. We studied the influence of t and Kt/V on survival in 262 patients on short‐daily hemodialysis (SDHD) and also noted death rate by weekday. Contingency tables, Kaplan‐Meier analysis, regression analysis, and stepwise Cox proportional hazard analysis were used to study the associations of clinical variables with survival. Patients had been on SDHD for a mean of 2.1 (range 0.1–11) years. Mean dialysis time was 12.9 ± 2.3 h/wk and mean weekly stdKt/V was 2.7 ± 0.5. Fifty‐two of the patients died (20%) and 8‐year survival was 54 ± 5%. In an analysis of 4 groups by weekly dialysis time, 5‐year survival continuously increased from 45 ± 8% in those dialyzing <12 hours to 100% in those dialyzing >15 hours without any apparent threshold. There was no association between Kt/V and survival. In Cox proportional hazard analysis, 4 factors were independently associated with survival: age in years Hazard Ratio (HR)=1.05, weekly dialysis hours HR=0.84, home dialysis HR=0.50, and secondary renal disease HR=2.30. Unlike conventional HD, no pattern of excessive death occurred early in the week during SDHD. With SDHD, longer time and dialysis at home were independently associated with improved survival, while Kt/V was not. Homedialysis and dialysis 15+ h/wk appear to maximize survival in SDHD.     

Intradialytic changes of serum magnesium and their relation to hypotensive episodes in hemodialysis patients on different dialysates

Magnesium is a crucial mineral, involved in many important physiological processes. Magnesium plays a role of maintaining myocardial electrical stability in hemodialysis patients. Intradialytic hypotension is a common complication of dialysis and it is more common with acetate dialysate. The significance of the intradialytic changes of magnesium and their relation to parathyroid hormone (PTH) level and calcium changes during dialysis, and their relation to hypotensive episodes during dialysis are interesting. The aim of this work is to investigate the intradialytic changes of serum magnesium in chronic hemodialysis patients with different hemodialysis modalities and the relation to other electrolytes and to PTH, and also the relation to intradialytic hypotension. The present study was conducted on 20 chronic renal failure patients. All patients were on regular hemodialysis thrice weekly 4 hr each using acetate dialysate (group I). To study the effect of an acetate-based dialysate vs. a bicarbonate-based dialysate on acute changes of magnesium, calcium, phosphorus, and PTH during a hemodialysis session, the same patients were shifted to bicarbonate dialysis (group II). All patients were subjected to full history and clinical examination, predialysis laboratory assessment of blood urea nitrogen (BUN), serum creatinine, albumin, and hemoglobin, serial assessment of magnesium, calcium, phosphorus, and parathyroid hormone at the start of the hemodialysis session, 2 hr later, and at the end of the session, blood pH, and electrocardiogram (ECG) presession and postsession. All patients were urged to fix their dry weight, diet, and current medications. None of the patients had diabetes, neoplasia, liver disease, or cachexia, nor had they been recently on magnesium-containing drugs or previously parathyroidectomized. Hemodialysis sessions were performed by volumetric dialysis machines using the same electrolyte composition. Magnesium level significantly increased in the bicarbonate group at the end of dialysis (0 hr: 2.73+/-0.87, 2 hr: 3.21+/-1.1, and at 4 hr: 5.73+/-1.45 mg/dL, p value <0.01), while it significantly decreased in the acetate group (0 hr: 3.00+/-0.58, 2 hr: 2.26+/-0.39, 4 hr: 1.97+/-0.33 mg/dL, p value <0.01). Calcium level significantly increased in the bicarbonate group (p=0.024) but not in the acetate group. Phosphorus level significantly decreased in both acetate and bicarbonate groups. PTH level did not significantly change in either group, p value > or =0.05. Blood pH significantly increased, changing from acidic to alkaline pH, with both modalities of hemodialysis. ECG showed no significant changes during sessions with either type of dialysate. Hypotension was significantly higher in group I compared with group II (p=0.01), and this hypotension was positively correlated with a decrease in serum magnesium level in group I. Intradialytic changes in serum magnesium have no correlation with intradialytic changes in serum calcium or with PTH level. However, it was significantly correlated with hypotension during the dialysis session, especially with acetate dialysate. Further investigations are needed to determine whether or not this is true in patients using bicarbonate dialysis.     

A primer for the prescription of short-daily and nocturnal hemodialysis

More frequent and intensive hemodialysis (HD) schedules continue to garner interest internationally. Two dominant regimens have emerged, namely short-daily and nocturnal HD. A growing body of observational data suggests that these regimens allow more rigorous control of biochemical and physical parameters when compared with conventional HD. This review describes the methodology used in providing more frequent or sustained HD both in center and at home, and attempts to provide a physiological rationale for the practices described in the current literature.     

International quotidian dialysis registry: Annual report 2010

The International Quotidian Dialysis Registry (IQDR) is a global initiative designed to study practices and outcomes associated with the use of hemodialysis (HD) regimens of increased frequency and/or duration. The IQDR grew out of the initiative that lead to the randomized prospective studies of nocturnal HD and short hours daily dialysis vs. conventional thrice weekly HD that are conducted by the Frequent Hemodialysis Network sponsored by the National Institutes of Health. These 2 separate studies are drawing to a close and the first results are expected to be reported later this year. These studies use surrogate outcomes for their primary endpoints as they are not powered to look at outcomes of mortality and hospitalization. The IQDR attempts to aggregate long‐term follow‐up data from centers utilizing alternative HD regimens worldwide and will have adequate statistical power to examine those important outcomes. To date, the IQDR has enrolled patients from Canada, the United States, Australia, New Zealand, and France and has linked with commercial databases and national registries. This sixth annual report of the IQDR describes: (1) An update on the governance structure; (2) The recommendations made at the first general meetings of the IQDR Scientific Committee and Advisory Board; (3) The status of those recommendations; (4) A summary of current data sources and participating registries; (5) The status of recruitment to date; (6) The creation of a specific Canadian IQDR data set and; (7) The current research agenda.     

Confounding factors for early death in incident end‐stage renal disease patients: Role of emergency dialysis start

Hemodialysis (HD) has been associated with higher 1‐year mortality than peritoneal dialysis (PD) after dialysis start. Confounding effects of late referral, emergency dialysis start, or start with central venous catheter on this association have never been studied concomitantly. Survival was studied among the 495 incident dialysed patients in our department from 1995 to 2006 and followed at least 1 year until December 31, 2007. Nested Cox models adjusted on patient characteristics explored factors associated with 1‐year and ≥1‐year mortality. Hemodialysis patients were 332 (67.1%), 104 (21.0%) were late referred (<6 months), 167 (33.7%) started dialysis in emergency, and 144 (29.1%) started with central venous catheter. When adjusted only on age, sex, and comorbidities, HD was associated with poor 1‐year outcome: adjusted hazard ratio (aHR) for death in HD vs. PD was 1.77, P=0.02. In fully adjusted model, among first dialysis feature variables, only emergency dialysis start was significantly associated with 1‐year mortality: aHR 1.53, P=0.02. Dialysis modality was not associated with 1‐year mortality rates in this fully adjusted model: aHR in HD vs. PD became 1.03, P=0.91. In ≥1‐year period, HD was associated with lower mortality than PD (aHR 0.61, P=0.004), whereas other first dialysis features were not associated with death. Other factors associated with death were age, type 2 diabetes, peripheral vascular disease, heart failure, and hepatic failure. Negative association between HD and 1‐year survival on dialysis was explained by confounders. Emergency dialysis start was strongly associated with early mortality on dialysis. Its prevention may improve patient survival.     

International quotidian dialysis registry: Annual report 2009

The International Quotidian Dialysis Registry (IQDR) is a global initiative designed to study practices and outcomes associated with the use of hemodialysis regimens of increased frequency and/or duration. Several small studies suggest that compared with conventional hemodialysis (HD), short-daily, nocturnal, and long conventional HD regimens may improve surrogate endpoints and quality of life. However, methodologically robust comparisons on hard outcomes are sorely lacking. The IQDR represents the first-ever attempt to aggregate long-term follow-up data from centers utilizing alternative HD regimens worldwide, and will have adequate statistical power to examine the effects of these regimens on multiple clinical endpoints, including mortality. To date, the IQDR has enrolled patients from Canada, the United States, Australia, and New Zealand, with plans in place to begin linking with additional commercial databases and national registries. This fifth annual report of the IQDR describes (1) a proposed governance structure that will facilitate international collaboration, stakeholder input and funding; (2) data sources and participating registries; (3) recruitment to date and patient baseline characteristics; and (4) an agenda for future research.     

The relevance of convection in clinical practice: a critical review of the literature

Convective treatments (high-flux hemodialysis (HD), hemodiafiltration and hemofiltration) are characterized by enhanced removal of middle and large molecular weight solutes compared with conventional low-flux HD. As these molecules are claimed to play an important role in the genesis of many complications of chronic HD, the availability of these techniques represented an intriguing innovation and a possible means to improve the still poor prognosis of HD patients. Here we will critically review the most important published studies comparing convective treatments with low-flux HD on chronic morbidity, preservation of residual renal function, and long-term survival.