High osmolar amino acid solution: an alternative to glucose?

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.”

An Amino Acid-Based Peritoneal Dialysis Fluid Buffered with Bicarbonate versus Glucose/Bicarbonate and Glucose/Lactate Solutions: An Intraindividual Randomized Study

Objective

In order to study acute metabolic changes and peritoneal transport, amino acids as osmotic agent and bicarbonate as buffer were tested as new agents in peritoneal dialysis (PD) solutions.

Design

In a prospective, cross-over, randomized, intraindividual study, we investigated the acute metabolic changes following the application of three different PD fluids: (1) a 1% amino acid-based PD solution buffered with bicarbonate (34 mmol/L) (Amino/Bic); (2) a 1.5% glucose anhydrous-containing bicarbonate-buffered solution (34 mmol/L) (Glu/Bic); and (3) a conventional 1.5% glucose anhydrous-based dialysis solution with lactate (35 mmol/L) (Glu/Lac).

Setting

University medical center.

Patients

Ten nondiabetic patients stable on continuous ambulatory peritoneal dialysis (time on dialysis, 42.5 ± 21.5 months) were treated and monitored with the test solutions over a 6-hour dwell. Three different study days followed in a randomized order for each patient (interval of 1 – 3 weeks). Blood and dialysate samples were taken at 0.25, 0.5, 1, 2, 4, and 6 hours. Immediately after the 1-hr dwell (and after sampling), the patients received a standardized breakfast, thereby simulating usual food intake.

Results

Following the application of Amino/Bic a significant increase in plasma amino acids occurred, with peak levels (maximum 250% increase) after either the 1-hr or the 2-hr dwell. Before taking the standard meal (0.5 hr, 1 hr), the mean serum glucose level with Amino/Bic was 8% ± 13% lower than with Glu/Bic ( p = 0.06) and 14% ± 8% lower than with Glu/Lac ( p < 0.01). This difference was still significant after the standard breakfast and also for the whole dwell (average serum glucose 0.5 – 6 hr: Amino/Bic, 91 ± 6 mg/dL; Glu/Bic, 100 ± 8 mg/dL; Glu/Lac, 102 ± 7 mg/dL; p < 0.01 MANOVA). The serum insulin profiles did not differ between the fluids. A transperitoneal protein- and amino acid-related nitrogen loss of 0.49 ± 0.18 g and 0.48 ± 0.12 g per dwell was measured using Glu/Bic and Glu/Lac, while a positive balance of 1.80 ± 0.43 g was achieved with Amino/ Bic. The parameters of acid-base status (pH, HCO3, pCO2) remained nearly unchanged in the blood, irrespective of the solution used, while dialysate values differed markedly. No significant differences with respect to ultrafiltration (Amino/Bic, –68 ± 199 mL/6hr; Glu/Bic, –51 ± 89 mL/6hr; Glu/ Lac, –2 ± 134 mL/6hr) and peritoneal creatinine clearance (Amino/Bic, 4.9 ± 0.6 mL/min; Glu/Bic, 5.1 ± 0.6 mL/min; Glu/ Lac, 4.8 ± 0.5 mL/min) were measured.

Conclusions

Our results demonstrate that ultrafiltration and small solute clearance over a 6-hour dwell with a 1% Amino/Bic solution were comparable to those of 1.5% Glu/Bic and 1.5% Glu/Lac. Reduced serum glucose concentrations were found with Amino/Bic and this fluid compensated the transperitoneal protein-nitrogen loss of about three glucose dwells. Bicarbonate buffering (34 mmol/L) did not change blood acid-base status combined with either glucose or amino acids.