Supplemented dialysis: amino acid-based solutions in peritoneal dialysis

Peritoneal dialysis is associated with several metabolic and nutritional abnormalities, some of which are related to the use of glucose-based solutions. Furthermore, the catabolic effects of uremia per se, protein and amino acid losses into the dialysate, peritonitis and poor appetite contribute to amino acid abnormalities, negative nitrogen balance and a high prevalence of malnutrition in peritoneal dialysis patients. To overcome these problems the use of amino acid instead of glucose as an osmotic agent has been proposed. Short-term studies have shown that amino acid-based solutions in peritoneal dialysis may supplement in excess the daily losses of amino acids during dialysis with glucose-based solutions. The amino acid solutions produce similar ultrafiltration and solute transport as the standard glucose solutions although the period of effective ultrafiltration is rather short. However, it should be noted that some studies have reported that the transport of small and large solutes may increase in patients using amino acid solutions. During the early 1980s several investigators have developed and tested different amino acid solutions for peritoneal dialysis. The initial clinical experience from Toronto with amino acid solutions containing large amounts of non-essential amino acids and inadequate amount of buffer were in general discouraging. The patients, who were not always malnourished and tended to have a low energy intake, developed increased BUN levels, acidosis, no improvement in nutritional status or amino acid abnormalities and, in some cases, anorexia. In 1985 a new 1% amino acid solution, containing an increased buffer amount and amino acids (mainly essential) in proportions which take the amino acid abnormalities in uremic patients into account, became available. The use of this solution resulted in some improvement in amino acid pattern and nutritional parameters, but acidosis and increased BUN levels remained problems. The experiences from these and previous studies showed that: (1) the improvement of the composition of amino acid solutions was beneficial; (2) a further increase of the buffer amount was needed; (3) patients included should have signs of protein malnutrition combined with low dietary protein intake to benefit from intraperitoneal amino acid supply, and (4) energy intake should be sufficient to prevent amino acids to end up as energy source. For this purpose a new improved 1.1% amino acid solution has been developed containing a further increase of some essential amino acids and an increased amount of lactate (40 mmol/l). This solution has been tested in malnourished patients eating 0.8 g protein/kg/day and 25-30 kcal/kg/day.(ABSTRACT TRUNCATED AT 400 WORDS)