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.

The Choice of Dialysis Solutions in Pediatric Chronic Peritoneal Dialysis: Guidelines by AnAD HOCEuropean Committee

Objective

To provide guidelines on choosing dialysis solutions for children on chronic peritoneal dialysis (PD).

Setting

European Paediatric Peritoneal Dialysis Working Group.

Data Source

Literature on the application of PD solutions in children ( Evidence), and discussions within the group ( Opinion).

Conclusions

Glucose is the standard osmotic agent for PD in children ( Evidence). The lowest glucose concentration needed should be used ( Opinion). Low calcium solution (1.25 mmol/L) should be applied, wherever possible, with careful monitoring of parathyroid hormone levels ( Opinion). The use of amino acid-containing dialysis fluids can be considered in malnourished children, although aggressive enteral nutrition is preferred ( Opinion). There is insufficient evidence documenting the efficacy of intraperitoneally administered amino acids ( Evidence). When ultrafiltration and/or solute removal are insufficient, poly-glucose solutions are a welcome addition to the treatment of children on nocturnal intermittent PD ( Evidence). However, in the absence of any reported long-term experience with children, their use must be closely monitored ( Opinion). Bicarbonate would appear to be the preferred buffer for PD in children, but more in vivo studies are required before it replaces the present lactate-containing solutions ( Evidence/Opinion).

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.

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.

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.