Rosemary Leitch

Calcium and phosphate balance with quotidian hemodialysis

BACKGROUND Conventional hemodialysis (HD) is associated with profound disturbances in calcium and phosphate metabolism and abnormal parathyroid hormone (PTH) levels. Effects of more frequent HD on calcium and phosphate balance have not been fully elucidated. METHODS The London Daily/Nocturnal Hemodialysis Study examined effects of quotidian HD, either daily HD (n = 11) or nocturnal HD (n = 12), on calcium and phosphate metabolism, bone alkaline phosphatase levels, and intact PTH (iPTH) levels. RESULTS Daily HD patients showed a slight decrease in predialysis serum phosphate levels, no changes in phosphate-binder requirements or serum calcium levels, and slight increases in serum bone alkaline phosphatase and iPTH levels. Nocturnal HD patients showed a trend for decreased predialysis phosphate levels, with significantly lower values than daily HD and matched control patients on conventional HD therapy at several times. Phosphate-binder use by nocturnal HD patients was significantly reduced. Both quotidian HD groups showed decreases in calcium x phosphate product, with significantly lower values for nocturnal HD patients (38.11 mg(2)/dL(2)) compared with daily HD and control patients (53.99 and 52.51 mg(2)/dL(2), respectively) at 18 months. Bone alkaline phosphatase levels increased slightly and attained statistical significance compared with baseline values for both quotidian HD groups. A trend for increases in serum iPTH levels, coupled with increasing levels of bone alkaline phosphatase in nocturnal HD patients, led to the decision to increase the dialysate calcium concentration from 5.0 to 7.0 mg/dL. This 1-time adjustment resulted in a reversal of the trend and a return to baseline values. CONCLUSION This study shows the superior control of serum phosphate levels in nocturnal HD patients compared with daily HD or conventional HD patients and the benefits of dialysate with a greater calcium concentration in slow nocturnal HD.

The London Daily/Nocturnal Hemodialysis Study--study design, morbidity, and mortality results.

BACKGROUND Despite the growing interest in more frequent hemodialysis (HD), to date, there have been no randomized prospective studies comparing outcomes in patients dialyzed using conventional thrice-weekly therapy with either the short hours daily or long slow nocturnal HD modalities. METHODS The London Daily/Nocturnal Hemodialysis Study, a prospective, comparative, nonrandomized study, directly compared outcomes of quotidian HD patients with conventional thrice-weekly HD patients. Patients were assigned to either daily HD (n = 11) or nocturnal HD (n = 12) and followed up for 5 to 36 months; all data were directly compared with matched control patients receiving conventional HD. This report describes the study design, morbidity and mortality results, and vascular access results. RESULTS There were no significant differences between patient groups in total numbers of hospital admissions or hospital days. Likewise, there was no significant difference in number of emergency visits per patient-year. There were 3 patient deaths in each of the nocturnal HD and control groups, although none of the deaths was deemed related to HD treatment. No deaths occurred in the daily HD group. Vascular access differences between study groups were not statistically significant. Among patients with arteriovenous (AV) fistulae, more than 80% of daily HD and nocturnal HD patients elected to use the buttonhole technique and successfully performed quotidian HD through their buttonhole at the 18-month follow-up. Patients with AV fistulae had the lowest annual rates of access complications and interventions. The annual access infection rate for quotidian HD patients using catheters decreased significantly after patients switched from in-center conventional HD to more frequent HD treatments at home. CONCLUSION Results from this comprehensive and pioneering study support the hypothesis that quotidian HD is more physiological than conventional HD and results in better patient outcomes.

Nocturnal but not Short Hours Quotidian Hemodialysis Requires an Elevated Dialysate Calcium Concentration

Interest in quotidian (daily) hemodialysis (HD) is growing. Some advocate short-hours high-efficiency daily HD (SDH) and others long-hours slow-flow nocturnal HD (NH) while the patient is asleep, both being used 5 to 7 d/week. The London Daily/Nocturnal Hemodialysis Study was the first attempt to obtain data of SDH and NH that may be compared with conventional thrice weekly HD (CH). This was a 4-yr observational study designed to enter and follow 40 patients: 10 receiving SDH, 10 receiving NH, and 20 receiving CH. The CH patients were cohort control subjects matched for each SDH and NH patient by age, gender, comorbidity, and original dialysis modality (in-center, home, self-care, or satellite HD). All SDH and NH treatments were at home. Data collection to December 2001 was analyzed. Then enrollment had been completed and all patients had been followed for 15 mo, eight SDH plus six NH for 18 mo, seven SDH plus six NH for 21 mo, and seven SDH and five NH for 24 mo. This report gives data on calcium and phosphorus metabolism in these patients. All patients were initially dialyzed against a 1.25-mmol/L calcium bath. Predialysis serum calcium levels became lower in NH versus SDH patients by the first month and at 9 mo were 2.67 +/- 0.25 mmol/L (M +/- SD) in SDH, 2.40 +/- 0.16 mmol/L in NH, and 2.52 +/- 0.21 mmol/L in CH (SDH versus NH, P = 0.038; SDH versus CH versus NH, NS). Predialysis phosphorus levels were better controlled by NH than by SDH or CH, and with NH, all phosphate binders were discontinued. By 12 mo, a rise in bone alkaline phosphatase was seen in NH patients (but not in SDH or CH patients), which peaked at 15 to 18 mo (NH 191 IU/L +/- 70; SDH 82 +/- 34; CH 80 +/- 36; P < 0.002) and similarly with intact parathyroid hormone (iPTH) levels (NH 159 pmol/L +/- 75; SDH 13.1 +/- 10; CH 18 +/- 18; P < 0.00001). Because of these changes, the dialysate calcium concentration was increased to 1.75 mmol/L for the NH patients. Postdialysis calcium then rose to 2.57 +/- 0.21, and alkaline phosphatase and iPTH normalized completely by 21 mo. These observations prompted mass balance studies that showed that a 1.25-mmol/L calcium dialysate was associated with a mean net calcium loss of 2.1 mmol/h of dialysis time, whereas 1.75-mmol/L calcium dialysate provides a net gain of 3.7 mmol/h. In addition, the mass balance studies showed that phosphate removal by NH (43.5 +/- 20.7 mmol) was significantly (P < 0.05) higher than by SHD (24.2 +/- 13.9 mmol) but not by CH (34.0 +/- 8.7 mmol) on a per-treatment basis. With the increased frequency of treatments provided by quotidian dialysis, the weekly phosphorus removal (261.2 +/- 124.2 mmol) by NH was significantly higher than by SDH (P = 0.014) and CH (P = 0.03). This allowed the discontinuation of P binders in the NH group, which in turn eliminated approximately 8 g elemental Ca/wk oral intake. This, together with a 4 g elemental Ca/wk dialysate loss induced by a 1.25-mmol/L Ca bath, explains the changes in Ca, alkaline phosphatase, and iPTH seen in the NH patients. The SDH patients have weekly dialysis times similar to CH and still require P binders and do not become Ca deficient using 1.25-mmol/L Ca dialysate. With NH but not SDH, an elevated dialysate Ca concentration is required.

Nursing Issues Related to Patient Selection, Vascular Access, and Education in Quotidian Hemodialysis

BACKGROUND Increased interest in quotidian hemodialysis (HD) programs requires that nephrology nurses have a larger role in transitioning patients to more frequent HD. Nursing issues include the selection, training, and education of patients before they begin more frequent HD therapy. METHODS The London Daily/Nocturnal Hemodialysis Study directly compared data from patients undergoing either short daily HD (n = 11) or long nocturnal HD (n = 12) with those undergoing conventional thrice-weekly HD (n = 22). Patient training, education, safety, and vascular access data were collected. RESULTS The patient training period varied from 10 to 25 days, with an average length of 16.64 days. Patients used 1 of 3 types of vascular access: native arteriovenous (AV) fistulae, grafts, or central catheters. No statistically significant differences in access flow rates between the study and control groups were noted or when comparing different types of access. A significant decrease in catheter infection rate was seen when patients switched to daily HD therapy. Patient cannulation surveys showed that patients with AV fistulae or grafts showed improvements with ease and comfort as the study progressed, and patients widely preferred the buttonhole technique to the rotating-needle method for cannulation. CONCLUSION With growing interest in the development of quotidian HD programs, HD nursing personnel face the exciting challenge of improving on existing training programs and treatment modalities.

Modifiable variables affecting interdialytic weight gain include dialysis time, frequency, and dialysate sodium

Interdialytic weight gain (IDWG) is associated with hypertension, left ventricular hypertrophy, and all‐cause mortality. Dialysate sodium concentration may cause diffusion gradients with plasma sodium and influence subsequent IDWG. Dialysis time and frequency may also influence the outcomes of this Na+ gradient; these have been overlooked. Our objective was to identify modifiable factors influencing IDWG. We performed a retrospective multivariable regression analyses of data from 86 home hemodialysis patients treated by hemodialysis modalities differing in frequency and session duration to determine factors involved that predict IDWG. Age, diabetic status, and residual renal function did not correlate with IDWG in the univariable analysis. However, using a combination of backwards selection and Akaike information criterion to build our model, we created an equation that predicted IDWG on the basis of serum albumin, age, patient sex, dialysis frequency, and the diffusive balance of sodium, represented by the product of the duration of dialysis and the patient plasma to dialysate Na+ gradient. This equation was internally validated using bootstrapping, and externally validated in a temporally distinct patient population. We have created an equation to predict IDWG on the basis of independent factors readily available before a dialysis session. The modifiable factors include dialysis time and frequency, and dialysate sodium. Patient sex, age, and serum albumin are also correlated with IDWG. Further work is required to establish how improvements in IDWG influence cardiovascular and other clinical outcomes.

Pre to post-dialysis plasma sodium change better predicts clinical outcomes than dialysate to plasma sodium gradient in quotidian hemodialysis.

Sodium balance across a hemodialysis treatment influences interdialytic weight gain (IDWG), pre‐dialysis blood pressure, and the occurrence of intradialytic hypotension, which associate with patient morbidity and mortality. In thrice weekly conventional hemodialysis patients, the dialysate sodium minus pre‐dialysis plasma sodium concentration (δDPNa+) and the post‐dialysis minus pre‐dialysis plasma sodium (δPNa+) are surrogates of sodium balance, and are associated with both cardiovascular and all‐cause mortality. However, whether δDPNa+ or δPNa+ better predicts clinical outcomes in quotidian dialysis is unknown. We performed a retrospective analysis of clinical and demographic data from the Southwestern Ontario Regional Home Hemodialysis program, of all patients since 1985. In frequent nocturnal hemodialysis, δPNa+ was superior to δDPNa+ in predicting IDWG (R2 = 0.223 vs. 0.020, P = 0.002 vs. 0.76), intradialytic change in systolic (R2 = 0.100 vs. 0.002, P = 0.02 vs. 0.16) and diastolic (R2 = 0.066 vs. 0.019, P = 0.02 vs. 0.06) blood pressure, and ultrafiltration rate (R2 = 0.296 vs. 0.036, P = 0.001 vs. 0.52). In short hours daily hemodialysis, δDPNa+ was better than δPNa+ in predicting intradialytic change in diastolic blood pressure (R2 = 0.101 vs. 0.003, P = 0.02 vs. 0.13). However, δPNa+ was better than δDPNa+ in predicting IDWG (R2 = 0.105 vs. 0.019, P = 0.04 vs. 0.68) and pre‐dialysis systolic blood pressure (R2 = 0.103 vs. 0.007, P = 0.02 vs. 0.82). We also found that the intradialytic blood pressure fall was greater in frequent nocturnal hemodialysis patients than in short hours daily patients, when exposed to a dialysate to plasma sodium gradient. These results provide a basis for design of prospective trials in quotidian dialysis modalities, to determine the effect of sodium balance on cardiovascular outcome.