Metabolic effects of incremental doses of intraperitoneal amino acids on automated peritoneal dialysis

The use of amino acid (AA) dialysate to ameliorate protein-energy malnutrition has been limited by adverse metabolic effects.

We undertook this study to examine the acute metabolic effects of escalating doses of AAs delivered with lactate/bicarbonate dialysate on automated peritoneal dialysis (APD).

12 APD patients were treated with conventional lactate-buffered dialysate (week 1), followed by lactate/bicarbonate-buffered dialysate (week 2), then 2 - 2.5 L 1.1% AA solution were added (week 3), and then an additional 2 - 2.5 L 1.1% AA were added (week 4). The primary outcomes were change in serum bicarbonate and pH, change in protein catabolic rate (PCR), and change in normalized ultrafiltration (milliliters/gram of carbohydrate infused).

Serum bicarbonate rose from week 1 to week 2 (28.9 +/- 3.2 vs 26.9 +/- 4.1 mmol/L, p = 0.03). Addition of one bag of AAs led to a decline in plasma bicarbonate (26.9 +/- 2.1 vs 28.9 +/- 3.2 mmol/L, p < 0.01), which was further magnified by the addition of the second bag of AAs (23.8 +/- 2.7 vs 26.9 +/- 2.1 mmol/L, p < 0.01). Serum bicarbonate fell significantly by week 4 compared to week 1 (23.8 +/- 2.7 vs 26.9 +/- 3.2 mmol/L, p < 0.01) although there was no significant change in venous pH or PCR when week 4 was compared to week 1. Normalized ultrafiltration was stable for the first 3 weeks but rose significantly in week 4 compared to week 1 (5.32 +/- 2.30 vs 4.14 +/- 1.58 mL/g, p = 0.03).

Higher doses of AAs mixed with newer bicarbonate/lactate dialysate on APD result in a small decrease in serum bicarbonate but improved normalized ultrafiltration. This merits further study as both a nutritional supplement and a glucose-sparing strategy.