Effectiveness and nutritional consequences of amino acid-based vs glucose-based dialysis solutions in infants and children receiving CAPD

Intraperitoneal Amino Acids: A Therapy Whose Time Has Come?

In regard to the question posed in the title of this review, the answer is mixed. IPN is possible today but only on a limited basis and at high cost with uncertain benefit. A 1.1% amino acid dialysis solution for IPAA therapy is available in several European countries but has not yet been approved for use in the United States. When it becomes more widely available, IP AA should become an important tool, along with other types of therapy, for use in the maintenance of good nutritional status in PDpatients.

Peritoneal Transport during Dialysis with Amino Acid-Based Solutions

Objective

To evaluate the potential clinical role of amino acids as an osmotic agent.

Design

The peritoneal transport of fluid, amino acids, and other solutes was investigated during a 6–hour single-cycle peritoneal dialysis with PDA 1% versus 1.36% glucose (n=6) or PDA 2.7% versus 3.86% glucose solution (n=9).

Patients

Fifteen stable nondiabetic continuous ambulatory peritoneal dialysis (CAPD) patients.

Results

The fractional absorption of the osmotic agents at 6 hours was higher with PDA 2.7% versus glucose 3.86% (p<0.005). The diffusive mass transport coefficient, KeD’ calculated for a period of dialysate isovolemia was higher with PDA 2.7% versus PDA 1% for essential, nonessential (p<0.005), and total (p<0.05) amino acids. The intraperitoneal volume-over-time curves and KqD values for urea, creatinine, glucose, albumin, β2microglobulin, and total protein did not differ between the amino acid solutions and the corresponding glucose solutions. KeD for urea was significantly higher during the dwell with PDA 2.7% versus PDA 1% (p<0.05). Plasma amino acid concentrations increased substantially during the first 1– 2 hours and then decreased gradually. Valine and methionine rose to 792% and 1119% of baseline values, respectively.

Conclusions

We conclude that the peritoneal transport of fluid and investigated solutes, except amino acids, was not different with the amino acid solutions compared with the corresponding equimolar glucose solutions. However, ultrafiltration tended to be lower with amino acid solutions. Furthermore, the fractional absorption of amino acids and KeD values for amino acids was higher with PDA 2.7% versus PDA 1 %, suggesting an effect of the hypertonic amino acid solution on the peritoneal membrane transport properties. Also, the hypertonic PDA2.7% solution yielded nonphysiologically high plasma levels of several amino acids. We therefore consider this solution not to be safe enough for long term clinical use.”

Continuous Ambulatory Peritoneal Dialysis (CAPD) of Children with Amino Acid Solutions: Technical and Metabolic Aspects

The changes in plasma and dialysate amino acids (AA) in 7 continuous ambulatory peritoneal dialysis (CAPD) children after dialysis with a 1% AA solution were compared with a glucose-containing solution. During the AA exchange, the plasma levels of individual AA reached their peaks after 1 h, with their percentage increments significantly correlated (p < 0.001) with the ratio of the amount of AA in the bag to the basal plasma concentration. The plasma concentration of methionine, valine, phenylalanine, and isoleucine remained higher than the basal value at 4 h. The amount of AA absorbed was 66% after 1 h, and 86% after 4 h and 6 h, corresponding to 2574 ± 253 μmollkg body wt. During glucose-dialysis (1.36%), levels of histidine, methionine, valine, phenilal-anine, and isoleucine were significantly decreased in plasma after 1 h, and stayed low throughout the dialysis period. The loss of AA with the peritoneal effluent was 116 ± 69 μmol/kg/body wt.

From this study, it seems that using an AA dialysis solution, with 1 exchange per day, might limit the daily glucose load and compensate for AA losses by supplying an extra amount of AA and by reducing the loss of other AA not contained in dialysis solutions. The AA pattern in plasma following AA-dialysis resembles that observed after a protein meal, with no signs of persistently high, nonphysiological levels.

Effects of Amino Acid Dialysis Compared to Dextrose Dialysis in Children on Continuous Cycling Peritoneal Dialysis

Objective

To compare the biochemical and nutritional effects of amino acid dialysis with dextrose dialysis in children receiving continuous cycling peritoneal dialysis (CCPD).

Design

A prospective randomized cross-over study.

Setting

Nonhospitalized patients.

Patients

Seven children aged 1.8 to 16.0 years (mean 8.1 years) with end-stage renal disease who were receiving CCPD.

Interventions

Each patient received nighttime automated CCPD of dextrose, plus a single daytime dwell of either amino acid dialysate or dextrose dialysate. After 3 months, subjects crossed over to the alternative regimen for a subsequent 3 months.

Main Outcome Measures

Creatinine clearance, ultra-filtration, urea, creatinine, electrolytes, total protein, albumin, fasting plasma amino acids, anthropometrics, total body nitrogen.

Results

Amino acid dialysis was comparable to dextrose dialysis for creatinine clearance and ultrafiltration. Plasma urea concentrations were higher during amino acid dialysis. No clinical side effects or worsening of metabolic acidosis was observed. Caloric intake increased and protein intake improved. Appetite and total body nitrogen increased in at least half the children during amino acid dialysis. Total plasma protein and albumin concentrations did not change significantly. Fasting plasma concentrations of amino acids after 3 months of amino acid dialysis were comparable to baseline values. For several amino acids, the dose-response curve was blunted after a single amino acid exchange following 3 months of amino acid dialysis, which may, in part, be due to the induction of hepatic enzyme synthesis.

Conclusions

Amino acid dialysis is an efficient form of peritoneal dialysis that should be considered for children with poor nutritional status for whom enteral nutrition supplementation has been unsuccessful. Further study is needed to determine the optimal amount of amino acids to deliver, the best time to administer the amino acid dialysis fluid, and the benefits of adding dextrose to the amino acid solution.

Effects of 3-Month Amino Acid Dialysis Compared to Dextrose Dialysis in Children on Continuous Ambulatory Peritoneal Dialysis

Objectives

To compare the nutritional and biochemical effects of amino acid dialysis to dextrose dialysis in children receiving continuous ambulatory peritoneal dialysis (CAPD).

Design

Prospective randomized crossover study.

Setting

Pediatric Nephrology Unit in a tertiary care, teaching hospital of the University of Toronto.

Patients

Seven children aged 0.7–16.5 years receiving CAPD. All patients had poor linear growth, with 5 patients showing evidence of energy deficit.

Interventions

Each patient received either amino acid or dextrose dialysate for 3 months, then crossed over to the alternate regimen for a subsequent 3 months.

Main Outcome Measures

Nutritional and biochemical data were obtained on each patient during each dialysis regimen.

Results

Analysis of the patients’ nutritional data showed comparable weight gain with both regimens but no significant improvement in lean body mass with either regimen. Appetite improved in most patients during amino acid dialysis. Biochemical data during amino acid dialysis showed a tendency to higher plasma potassium and urea levels with no clinical side effects or worsening of acidosis; however, there was a reduced anion gap and increased total plasma protein, due mostly to a rise in plasma albumin and a smaller increase in immunoglobulins. With the exception of tryptophan, fasting amino acid levels at the start and end of amino acid dialysis did not show any significant change. An interesting phenomenon of early blunting of the rise in amino acid levels, following a single amino acid dialysate exchange, was noticed at the end of the amino acid dialysis period. This newly described phenomenon could have been due to tolerance or hepatic enzyme induction.

Conclusions

Overall amino acid dialysis was comparable to dextrose dialysis with no additional proven nutritional benefit, was equally effective in ultrafiltration and creatinine clearance, and produced no adverse clinical or biochemical effects.

Effect of Short-Term Essential Amino Acid-Containing Dialysate in Young Children on CAPD

In young children on CAPD, hypoproteinemia and malnutrition are often observed. We used essential amino acid-containing dialysate (EMD) to assess short-term effectiveness on serum amino acid concentrations in young children undergoing CAPD. EMD consisted of a 540 ml, 1.5% glucose-containing dialysate and 100 ml of 7.4% essential amino acid (EM) solution. Aside from methionine, all serum EM rose during the 6 hour peritoneal dialysis cycle using EMD, peaking at about 200% of pre-treatment level one hour after start of treatment. They then returned to near pre-treatment levels at the end of the cycle. However, serum methionine increased 680% of pre-treatment level, one hour after start and 390% at the end of the cycle. In the serum non-EM tyrosine, which showed low levels in patients with chronic renal failure, increased after EMD treatment. Other non-EM, most of which showed increased levels in patients with chronic renal failure, decreased after EMD treatment. These changes in serum amino acids suggest that EM, absorbed from EMD, may have increased uptake of non-EM in protein synthesis. This may improve the nutritional status of young children on CAPD.

Nutritional Status in Children Receiving Chronic Peritoneal Dialysis

Chronic peritoneal dialysis (CPD), widely used in uremic children, may have contrasting effects on the nutritional status of patients. Metabolic and nutritional abnormalities due to the combined effects of uremia per se, glucose absorption from the dialysate and catabolic factors, such as protein and amino acid losses into dialysate, poor appetite, and recurrent episodes of peritonitis are the most important.

Although CPD allows for fewer dietary restrictions and supplies an extra amount of calories by glucose absorbed with the peritoneal fluid, when protein and energy intakes are assessed the protein intake was almost sufficient or more than that prescribed, whereas the energy intake was low.

In CPD children the standard deviation score for weight, height, triceps skinfold thickness, and midarm circumference has been reported as more severely impaired in children less than ten years old. Anthropometric parameters did not worsen during CPD treatment.

Plasma proteins and albumin are reported as being low in CPD children. The dietary intake and protein losses have been considered to be the most important determinants of the albumin level in CPD patients.

The reported average dialysate losses of free amino acids (AA) during CPD in children vary from 0.02 to 0.03 g/kg/day in different studies. The patterns of plasma AA in CPD is represented by reduced levels of branched chain AA and of other essential amino acids and increased concentrations of some nonessential AA. Several factors may influence plasma AA profile: uremia per se, hormonal alterations, protein and AA losses, and dietary intake. A more specific uremic AA pattern is found in muscle, the largest pool of free AA in the body. Studies on muscle AA in adults on CPD are conflicting: some authors have reported several muscle AA alterations, but others have shown an almost normal pattern. Low valine and leucine muscle levels have been reported in children on CPD.

Amino-Acid-Based Continuous Ambulatory Peritoneal Dialysis (CAPD) Fluid over Twelve Weeks: Effects on Carbohydrate and Lipid Metabolism

Aspects of lipid and carbohydrate metabolism were studied in 8 patients established on continuous ambulatory peritoneal dialysis (CAPD) with plasma albumin < 35 g/L, before, during, and after substitution of 1 of the daily glucose exchanges by a commercial 1 % amino acid dialysis fluid for 12 weeks. The amount of glucose absorbed from the dialysis fluid was consequently reduced by about 25%, hence total energy intake decreased by about 100 Kcallday, but peritoneal glucose transfer kinetics were unaffected. Glucose was lost into amino acid dialysate as expected (2 g/day).

Excluding 1 patient with a large rise in calorie intake, total and LDL cholesterol fell at 8 and 12 weeks (LDL cholesterol week 0, 5.26 ± 1.13; week 8, 4.32 ± 0.74; week 12,4.30 ± 1.22; mean ± SD, p < 0.01 for both), but returned to baseline 2 weeks after the restoration of glucose fluid (LDL 4.91 ± 1.22, p < 0.05 vs. week 12). Apolipoprotein B concentration also fell at 12 weeks (p < 0.01). No changes were seen in body weight, body fat, arm muscle circumference, fasting plasma glucose, insulin, growth hormone, triglyceride, non esterified fatty acids, or HDL cholesterol. The response of these biochemical indices to single 8-h glucose and amino acid morning exchanges at 0 and 12 weeks were studied. After 12 week's use of amino acid dialysis fluid, plasma cholesterol and apolipoprotein B were significantly lower throughout the exchange.

The decrease in cholesterol and apolipoprotein B during the substitution of 1% amino acid dialysis fluid may be associated not only with the reduction in glucose intake, but also with a gradual change in lipid metabolism. The routine use of such solutions may lower cardiovascular morbidity and mortality in CAPD but further evaluation is indicated.

The Use of Alternative Peritoneal Dialysis Solutions in Pediatric Patients

Changes in the formulation of peritoneal dialysis solutions will continue. For the present, dextrose dialysis will remain the osmotic solute of choice. How amino acids and glucose polymers as solute replace ments for glucose fit into the dialysis prescription remains to be seen. The lower concentration of calcium and magnesium appears to be gaining acceptance in many centers. It is feasible that in the next few years the challenge of adding bicarbonate to the peritoneal dialysis solution will be circumvented, because there appears to be a real clinical need for such an improvement. Pediatric modifications will be necessary, appreciating that such changes will have an economic penalty, and thus must have proven value.

Nutrition assessment and management in children on peritoneal dialysis

Protein-calorie malnutrition, otherwise known as cachexia, is a common problem in children undergoing chronic peritoneal dialysis (PD) and is a frequent source of significant morbidity and mortality. Recent evidence suggests that the main factors involved in the pathogenesis are metabolic acidosis, a decreased response to anabolic hormones, and chronic inflammation, associated with hormonal imbalances and an increased metabolic rate. Given the complexity and multifactorial nature of cachexia, the assessment of nutritional status in children on PD requires a complete history and physical examination; assessment of dietary intake, biochemical indices, and anthropometry; and possibly bioimpedance analysis and combined score systems. Its management should likewise be multidisciplinary and include ensuring an adequate energy and protein intake; optimal metabolic control, with the correction of acidosis, anaemia, and hyperparathyroidism; an optimal (or at least adequate) dialysis dose; and, if necessary, prescription of specific drugs such as recombinant human growth hormone.

Use of new peritoneal dialysis solutions in children

Standard peritoneal dialysis (PD) solutions with low pH and containing high concentrations of lactate and glucose have been demonstrated to negatively affect the peritoneal membrane, mesothelial cell viability, residential peritoneal cells, and also to inhibit phagocytic functions. An increasing body of experimental evidence supports the idea that the peritoneal hypervascularization and fibrosis observed in long-term PD are causally related to the acute and chronic toxicity of conventional PD solutions. A Physioneal (lactate/bicarbonate mixed buffer pH 7-7.4), Physioneal, Extraneal (7.5% icodextrin), Nutrineal (1.1% amino-acid-containing solution) regimen, for example, offers a significant reduction in carbohydrate load (approximately 40-50%), lower exposure to and absorption of glucose degradation products, reduced oxidative stress, and improved volume control when compared with a first-generation DDDD (4 x Dianeal) regimen. The positive aspects of each solution that we have observed in our patients allow a recommendation on the potential benefit of using these solutions in children treated with PD. In fact, data from the literature as well as the results of the studies reported in this paper show that in children the application of neutral pH bicarbonate/lactate-buffered solution for the standard nighttime APD prescription, icodextrin solution for a long daytime dwell, and AA-based solution in malnourished patients is safe and effective. Extended clinical trials should be encouraged to better define the PD schedules for the combined use of these solutions that may be associated with the best clinical efficacy and the highest level of biocompatibility.

Nutrition in children with CRF and on dialysis

The objectives of this study are: (1) to understand the importance of nutrition in normal growth; (2) to review the methods of assessing nutritional status; (3) to review the dietary requirements of normal children throughout childhood, including protein, energy, vitamins and minerals; (4) to review recommendations for the nutritional requirements of children with chronic renal failure (CRF) and on dialysis; (5) to review reports of spontaneous nutritional intake in children with CRF and on dialysis; (6) to review the epidemiology of nutritional disturbances in renal disease, including height, weight and body composition; (7) to review the pathological mechanisms underlying poor appetite, abnormal metabolic rate and endocrine disturbances in renal disease; (8) to review the evidence for the benefit of dietetic input, dietary supplementation, nasogastric and gastrostomy feeds and intradialytic nutrition; (9) to review the effect of dialysis adequacy on nutrition; (10) to review the effect of nutrition on outcome.

Metabolic consequences of peritoneal dialysis

Optimization of the peritoneal dialysis (PD) prescription includes attempts to normalize the patient's blood pressure and extracellular volume. To do so, one must utilize crystalloid or colloid osmotic agents to achieve ultrafiltration. These osmotic agents are systemically absorbed and thus have both potential benefits and adverse effects. With glucose-based dialysate solutions, the average patient absorbs 300-450 kcal of glucose per day on either continuous ambulatory peritoneal dialysis (CAPD) or the cycler. The amount of glucose absorbed varies based on peritoneal transport characteristics, prescription, and tonicity of fluids used. Alternative osmotic agents such as amino acids and macromolecular solutions, including polypeptides and polyglucose (icodextrin) solutions, have a different rate of systemic absorption and thus a different caloric load profile. In addition, there are protein losses that average about 10 g/day with glucose-based solutions and glucose losses with either amino acid or icodextrin dialysate solutions. There are also potential advantages of these alternative solutions with regard to ultrafiltration. Glucose-based solutions require the development of significant crystalloid osmotic forces, which are dissipated as glucose is absorbed systemically. In contrast, macromolecular solutions achieve ultrafiltration via differences in colloid osmotic pressure, and the absorption of these agents is of a lesser magnitude than glucose-based solutions. Further research is needed to determine other potential risks and benefits of these alternative dialysate solutions.

Acute effects of simultaneous intraperitoneal infusion of glucose and amino acids

BACKGROUND

The feasibility of simultaneously infusing glucose and amino acid (AA)-based peritoneal dialysis solutions was tested to determine whether peritoneal dialysis patients could achieve an adequate nonprotein calorie/nitrogen ratio while preventing a marked increase in blood urea nitrogen (BUN), which is usually seen if the AAs are administered without glucose.

METHODS

An automatic peritoneal dialysis cycler was used to infuse glucose and AA solutions (3:1) simultaneously during the night. Eight infusions of 1000 mL m2 of body surface area (BSA), with a 60 minute dwell time, were performed in 10 children on peritoneal dialysis. The dialytic effluent was analyzed at every exchange and totaled at eight hours to evaluate volume, glucose, and AA concentration. Blood samples for plasma, glucose, insulin, and free AA determination were drawn at the beginning of automated peritoneal dialysis (APD) session and at each instillation of peritoneal dialysate.

RESULTS

The mean glucose absorption was 33.7 +/- 10.0% and the AA absorption was 55.2 +/- 13.2% of the infused amount, and the ratio of nonprotein calorie (derived from glucose) to nitrogen (derived from AA) was 115.4:1. The insulin levels returned to normal only three hours after the beginning of APD. The free AA plasma levels were already increased two hours after dinner and remained high for the entire APD treatment because of the continuous absorption of AA from the peritoneum. The BUN levels did not increase despite the supply of AA.

CONCLUSIONS

This APD procedure may improve utilization of AA for protein synthesis, as suggested by the lack of increase of the BUN levels with this regimen.

Effect of amino acid administration on uremic muscle metabolism: a 31P-spectroscopy study

The effect of a six-month peritoneal amino acid administration on muscle metabolism at rest and during exercise was examined in 12 patients (4 control and 8 amino acid treated) on continuous ambulatory peritoneal dialysis. 31P-magnetic resonance spectroscopy was used to measure several high-energy phosphates (PCr, Pi) in resting muscle and during exercise and recovery. At rest, no significant changes were detected between the non-treated (control) and the amino acid treated (experimental) group. Before the administration of amino acids, the exercise-induced fall in [PCr], the increase in [ADP] and [Pi] and the pH were not significantly different in the control and experimental group. The initial rate of PCr recovery and the calculated maximal rate of ATP-synthesis (Qmax) for the control subjects was not significantly different at the onset and the end of the study. In the treated group, however, the fall in [PCr] and increase in [ADP] after exercise were significantly lower after than before treatment, while [Pi] and pH were identical. The initial rate of PCr recovery and Qmax were also significantly improved. These changes indicate an improved oxidative phosphorylation under the treatment and suggest that the impaired oxidative metabolism of the dialysis patients could be the result of their bad nutritional state.

Continuous ambulatory peritoneal dialysis: a review of its mechanics, advantages, complications, and areas of controversy

OBJECTIVE

The primary objective of this article is to review the mechanics, advantages, complications, pharmacokinetics, and future trends of continuous ambulatory peritoneal dialysis (CAPD) as they pertain to pharmacotherapy.

DATA SOURCES

Pertinent articles were obtained from an English-language literature search using MEDLINE (1980-1991), Index Medicus (1987-1990), and bibliographic reviews of review articles. Indexing terms included peritoneal dialysis, pharmacokinetics, peritonitis, vancomycin, and fluoroquinolones.

DATA SYNTHESIS

All clinical studies comparing organism recovery methods and treatment of peritonitis have methodologic limitations (e.g., comparison of disparate patient groups, different definitions of peritonitis, lack of follow-up, lack of control for sterile cultures) that may affect the reported results.

CONCLUSIONS

CAPD is an alternative to hemodialysis for the treatment of endstage renal disease and has many complications, leading to significant morbidity. This indicates that CAPD is not appropriate for all patients. Using blood-culturing techniques to culture for dialysate is most productive, but also the most costly. There are few data to indicate exactly the drugs, doses, and durations of choice for peritonitis. Both intraperitoneal and oral administration appear to be appropriate.

Nutritional support in renal failure

Adequate protein intake is necessary in renal failure to reduce morbidity. The desire to avoid dialysis should not be a justification to starve patients, particularly because fed patients have better survival rates in acute renal failure. The treatment techniques for renal failure may be used secondarily as a delivery route for nutrients.

Long-term effect of amino-acid dialysis solution in children on continuous ambulatory peritoneal dialysis

The study involved eight metabolically stable children, with chronic renal failure on continuous ambulatory peritoneal dialysis (CAPD) whom we followed for 12-18 months. For the first 6 months CAPD was performed with dextrose; for the subsequent 6-12 months the morning exchange was substituted with a 1% amino-acid (AA) solution. The following parameters did not change during the study: serum creatinine, uric acid, inorganic phosphate, serum bicarbonate, potassium, cholesterol, triglycerides, total protein, albumin and transferrin. The only parameter that changed was blood urea nitrogen, which increased moderately. The anthropometric parameters did not show significant variation before and after AA dialysis. The plasma AA profile, which under basal conditions showed lower levels of several essential AAs, improved during the treatment period, with a partial correction of the imbalance. It is possible that this correction of plasma AAs may positively influence the metabolism of some organs such as the brain, muscle and those of the hepatosplanchnic region. The intracellular pool of free AAs, measured in polymorphonuclear leucocytes, was severely altered before the treatment and after 6 and 12 months showed only minor variations. It is possible that some modifications in the proportion of the different AAs in the dialysis solution or an improvement in the concentration or in the number of exchanges per day are necessary in order to change the nutritional status and to modify the intracellular AA pool.

Zinc absorption from glucose and amino acid dialysis solutions in children on continuous ambulatory peritoneal dialysis (CAPD)

Zinc deficiency in children with chronic renal failure may be due to inadequate intake or excessive losses. To determine the effect of dialysate solute type and concentration on the net absorption or loss of zinc from the peritoneal cavity, six CAPD patients ages 9-19 years were dialyzed with 1.3% and 2.3% amino acid-containing dialysis solutions and 2.5% and 4.25% glucose-containing solutions on four separate occasions. Zinc contamination of the initial effluent dialysis solutions was quite high (17.1 +/- 7.7 micrograms/dl) but did not differ between the four solutions. Significantly higher zinc retention was documented with the glucose-containing dialysis solutions compared to the amino acid-containing solutions (99.8 +/- 32.7 vs. 28.3 +/- 51.3 micrograms, 2.5% G vs 1.3% AA, p less than 0.01; 146.0 +/- 112.6 vs. 23.0 +/- 84.3, 4.25% G vs 2.3% AA, p less than .01). Although the mechanism is unclear, results of this study confirm in children that there is significant net absorption of zinc from glucose containing dialysis solutions at both high and low glucose concentrations. Thus, CAPD does not contribute to zinc depletion. Solute concentration did not affect net zinc absorption; thus it appears that movement of zinc across the peritoneum is dependent on solute type (amino acid or glucose) and independent of the osmolality.