Impact of Fill Volume on Peritoneal Clearances and Cytokine Appearance in Peritoneal Dialysis

Background

Current adequacy guidelines for peritoneal dialysis encourage the use of large fill volumes for the attainment of small solute clearance targets. These guidelines have influenced clinical practice in a significant way, and adoption of higher fill volumes has become common in North America. Several studies, however, have challenged the relevance of increasing small solute clearance; this practice may result in untoward consequences in patients.

Objective

The present study was designed to explore the relationship between dialysate volume and the clearance of different sized molecules, fluid dynamics, and appearance of peritoneal cytokines.

Methods

Thirteen adult prevalent patients on continuous ambulatory peritoneal dialysis were studied. Three different dialysate volumes (2.0, 2.5, and 3.0 L) were infused on consecutive days in a random order. Several measurements of peritoneal fluid dynamics (intraperitoneal pressure, net ultrafiltration, fluid absorption), solute clearances (urea, creatinine, β2-microglobulin, albumin, IgG, and transferrin), and appearance of interleukin-6 and tumor necrosis factor alpha (TNFα) were assessed.

Results

Increase in dialysate fill volume (from 2 to 2.5 to 3 L) was examined in relationship to body surface area (BSA). The dialysate volume/BSA (DV/BSA) ratio increased from 1262 to 1566 to 1871 mL/m2 on 2.0, 2.5, and 3.0 L dialysate volumes, respectively. In parallel, diastolic blood pressure increased from 82.7 ± 8.8 to 87.0 ± 9.5 to 92 ± 8.3 mmHg ( p < 0.05). Net ultrafiltration rate also increased, from 0.46 ± 0.48 to 0.72 ± 0.42 to 0.97 ± 0.49 mL/minute ( p < 0.01), despite a concomitant increase in fluid absorption, from 1.05 ± 0.34 to 1.21 ± 0.40 to 1.56 ± 0.22 mL/min ( p < 0.01). Urea peritoneal clearance increased from 8.27 ± 0.68 to 9.92 ± 1.6 to 12.98 ± 4.03 mL/min ( p < 0.01); creatinine peritoneal clearance increased from 6.69 ± 1.01 to 7.64 ± 1.12 to 8.69 ± 1.76 mL/min ( p < 0.01). Clearance of the other measured molecules did not change. Appearance of interleukin-6 increased 17% and 43% ( p < 0.01), and TNFα appearance increased 14% and 50% ( p < 0.01) when dialysate volumes of 2.5 and 3.0 L were used, compared with 2.0 L.

Conclusions

These results show that, with higher values of DV/BSA ratio, small solute peritoneal clearance is increased, but clearances of large molecules remain unchanged. With the use of higher volumes, fluid absorption rate and the appearance of proinflammatory cytokines in the dialysate are increased.

Effect of icodextrin on heart rate variability in diabetic patients on peritoneal dialysis

INTRODUCTION

Spectral analysis of heart rate variability is a noninvasive method for evaluating autonomic cardiovascular dysfunction under various clinical conditions, such as in dialysis patients, in whom an imbalance between the sympathetic and parasympathetic nervous system appears to be an important risk factor for sudden cardiovascular death and arrhythmia. ♢

OBJECTIVE

We compared the effect of icodextrin-based dialysis solution, an option that allows for better metabolic and fluid overload control, with that of glucose-based dialysis fluid on sympathetic and parasympathetic activity in the heart, as assessed by heart rate variability, in diabetic patients on peritoneal dialysis (PD). ♢

METHODS

This secondary analysis uses data from a randomized controlled trial in diabetic PD patients with high or high-average peritoneal transport using icodextrin-based (ICO group, n = 30) or glucose-based (GLU group, n = 29) solutions for the long dwell. All patients underwent 24-hour electrocardiographic Holter monitoring at baseline, and at 6 and 12 months of follow-up. ♢

RESULTS

We observed no significant differences between the groups in most of the variables analyzed, although values were, in general, below reference values. In the ICO group, total power and both low- and high-frequency power in normalized units increased, but the percentage of RR intervals with variation of more than 50 ms declined over time; in the GLU group, all those values declined. Plasma catecholamine levels were higher at baseline and declined over time. ♢

CONCLUSIONS

These results indicate a partial recovery of sympathetic activity in the ICO group, probably because of better extracellular fluid control and lower exposure to glucose with the use of icodextrin-based dialysis solutions.

Impact of fill volume on peritoneal clearances and cytokine appearance in peritoneal dialysis

BACKGROUND

Current adequacy guidelines for peritoneal dialysis encourage the use of large fill volumes for the attainment of small solute clearance targets. These guidelines have influenced clinical practice in a significant way, and adoption of higher fill volumes has become common in North America. Several studies, however, have challenged the relevance of increasing small solute clearance; this practice may result in untoward consequences in patients.

OBJECTIVE

The present study was designed to explore the relationship between dialysate volume and the clearance of different sized molecules, fluid dynamics, and appearance of peritoneal cytokines.

METHODS

Thirteen adult prevalent patients on continuous ambulatory peritoneal dialysis were studied. Three different dialysate volumes (2.0, 2.5, and 3.0 L) were infused on consecutive days in a random order. Several measurements of peritoneal fluid dynamics (intraperitoneal pressure, net ultrafiltration, fluid absorption), solute clearances (urea, creatinine, beta2-microglobulin, albumin, IgG, and transferrin), and appearance of interleukin-6 and tumor necrosis factor alpha (TNFalpha) were assessed.

RESULTS

Increase in dialysate fill volume (from 2 to 2.5 to 3 L) was examined in relationship to body surface area (BSA). The dialysate volume/BSA (DV/BSA) ratio increased from 1262 to 1566 to 1871 mL/m2 on 2.0, 2.5, and 3.0 L dialysate volumes, respectively. In parallel, diastolic blood pressure increased from 82.7 +/- 8.8 to 87.0 +/- 9.5 to 92 +/- 8.3 mmHg (p < 0.05). Net ultrafiltration rate also increased, from 0.46 +/- 0.48 to 0.72 +/- 0.42 to 0.97 +/- 0.49 mL/minute (p < 0.01), despite a concomitant increase in fluid absorption, from 1.05 +/- 0.34 to 1.21 +/- 0.40 to 1.56 +/- 0.22 mL/min (p < 0.01). Urea peritoneal clearance increased from 8.27 +/- 0.68 to 9.92 +/- 1.6 to 12.98 +/- 4.03 mL/min (p < 0.01); creatinine peritoneal clearance increased from 6.69 +/- 1.01 to 7.64 +/- 1.12 to 8.69 +/- 1.76 mL/min (p < 0.01). Clearance of the other measured molecules did not change. Appearance of interleukin-6 increased 17% and 43% (p < 0.01), and TNFalpha appearance increased 14% and 50% (p < 0.01) when dialysate volumes of 2.5 and 3.0 L were used, compared with 2.0 L.

CONCLUSIONS

These results show that, with higher values of DV/BSA ratio, small solute peritoneal clearance is increased, but clearances of large molecules remain unchanged. With the use of higher volumes, fluid absorption rate and the appearance of proinflammatory cytokines in the dialysate are increased.

[Effect of zinc supplements on the nutritional status of patients undergoing continuous ambulatory peritoneal dialysis]

OBJECTIVE

To test the effect of zinc supplementation on the nutritional status of patients on continuous ambulatory peritoneal dialysis (CAPD).

MATERIAL AND METHODS

Double-blinded randomized controlled clinical trial. Twenty-five patients with end stage renal disease (ESRD) on CAPD program, from 16 to 60 years old were studied. Two weeks before the beginning of the study all the drugs with a known effect on zinc absorption were withdrawn. Patients were randomly allocated into one of two groups. The control group consisted of 12 patients receiving placebo, and the intervention group of 13 patients receiving 100 mg/day of elemental zinc for 3 months. The diet was individually adjusted to 35 kcal/kg/day, and 1.5 g/day of proteins. Subjective global assessment (SGA), anthropometric measurements, electric bioimpedanciometry, measurements of albumin, prealbumin, and transferrin, and evaluation of energy, proteins, carbohydrates, and lipids consumption were done to classify the nutritional status at the beginning and at the end of the study. Therapeutic compliance was assessed by measuring plasma zinc levels and by capsule counting.

RESULTS

There were no statistically significant differences between groups regarding age, gender, time on CAPD, and ESRD causes. The proportion of patients classified as well nourished, or with mild or moderate malnutrition by SGA did not show significant differences between the group receiving Zn supplementation and the group receiving placebo. Anthropometric measurements and body composition assessed by bioelectric impedance were similar in the two groups. In the control group, serum levels of albumin (3,621 +/- 838 vs. 3,068 +/- 842 mg/dL), prealbumin (49 +/- 14 vs. 44 +/- 12 mg/dL), and transferrin (238 +/- 94 vs. 195 +/- 79 mg/dL) decreased significantly at the end of the follow-up period respect to the baseline values (p < 0.05). In the intervention group albumin (3,320 +/- 910 vs. 2,696 +/- 964 mg/dL), prealbumin (43 +/- 9 vs. 38 +/- 8 mg/dL), and transferrin (236 +/- 99 vs. 193 +/- 66 mg/dL) also decreased significantly (p < 0.05). In the control group baseline zinc level was low (60 +/- 5 micrograms/dL) and remained stable along the follow-up period, while in the intervention group it increased from 52 +/- 5 (baseline) to 92 +/- 9 micrograms/dL (end of the follow-up, p < 0.05).

CONCLUSIONS

Zinc supplementation did not improve the nutritional status in patients on CAPD.