Michael R. Jones

Treatment of malnutrition with 1.1% amino acid peritoneal dialysis solution: Results of a multicenter outpatient study

A peritoneal dialysis (PD) solution containing 1.1% amino acids as the osmotic agent was evaluated in a 3-month randomized, prospective, open-label study in malnourished PD patients. Patients in the treatment group (DAA) received one or two exchanges daily with the amino acid solution, depending on tolerance, in place of glucose solutions. Controls (DD) received their usual therapy with glucose dialysate. Fifty-four DAA and 51 DD patients completed the study. In DAA, but not in DD patients, there was a significant increase at month 3 in serum insulin-like growth factor-1 (IGF-1) levels and significant decreases in serum potassium (all 3 months) and inorganic phosphorus levels (months 1 and 3), indicating a general anabolic response. Prealbumin and transferrin levels were significantly increased in DAA but not in DD patients at month 1, but the groups did not differ at months 2 and 3. In patients with baseline albumin levels less than 3.5 g/dL (bromcresol green [BCG] method), DAA patients showed increases in albumin, transferrin (months 1 and 2), and prealbumin levels (all 3 months) relative to baseline values, whereas these serum protein levels were unchanged in DD patients, although the changes from baseline did not differ between groups. In this subgroup, midarm muscle circumference (MAMC) did not change in DD or DAA patients. In patients with baseline albumin levels of 3.5 g/dL or greater, DD patients had decreases in albumin and total protein levels at all 3 months and in prealbumin levels at months 1 and 2, relative to baseline. In DAA patients, there were fewer changes in serum proteins. MAMC increased significantly from baseline in DAA but not in DD patients, although changes from baseline did not differ between DAA and DD groups. DAA patients showed no changes in peritoneal membrane transport characteristics. The results indicate that treatment with one or two exchanges daily of this amino acid-based PD solution is safe and provides nutritional benefit for malnourished PD patients.

Etiology of Severe Malnutrition: Results of an International Cross-Sectional Study in Continuous Ambulatory Peritoneal Dialysis Patients

In an international cross-sectional study of 224 continuous ambulatory peritoneal dialysis (CAPD) patients, 59% were well nourished but 8% had severe malnutrition. To investigate factors that might underlie the severe malnutrition, we analyzed these data further. Forty-one percent of well-nourished patients had no residual renal function (RRF). Compared with well-nourished patients who had RRF, patients with no RRF received more dialysis, but not enough to compensate completely for loss of RRF. In addition, well-nourished patients with no RRF had a lower protein catabolic rate (PCR) than patients with RRF, although somatic and visceral protein stores were similar in the two groups. Compared with well-nourished patients with no RRF, severely malnourished patients, 94% of whom had no RRF, were prescribed and were receiving a lower total volume of dialysate. The latter had actual body weights (ABWs) that were considerably less than their desirable body weights (DBWs) due to recent losses of somatic protein and fat stores, whereas well-nourished patients were at or near their DBWs. Urea clearance, normalized to 0.58 x ABW, was similar in well-nourished and severely malnourished patients with no RRF, but was significantly decreased in severely malnourished patients when normalized to 0.58 x DBW. This suggests that in severely malnourished patients no compensation had been made for their loss of RRF, and they may have been chronically underdialyzed. The PCR, normalized to ABW, was similar in well-nourished and severely malnourished patients. Thus, the severely malnourished patients were not eating the additional protein that would have been required to restore good protein status.(ABSTRACT TRUNCATED AT 250 WORDS)

Essential carbamoyl-amino acids formed in vivo in patients with end-stage renal disease managed by continuous ambulatory peritoneal dialysis : Isolation, identification, and quantitation

Carbamoyl-amino acids (C-AA) are formed by reaction of amino acids with cyanate, which is spontaneously formed from urea at body temperature and pH. In vivo derivatized C-AA are not measured by the usual amino acid analysis methods, which require a free amino group for derivatization. Free-amino acids (F-AA) but no C-AA were found in the postabsorptive plasma of eight normal persons with blood urea nitrogen (BUN) levels ranging from 9 to 16 mg/dl. In a longitudinal study of postprandial plasma (n=43), essential amino acids, both C-AA and F-AA, were isolated and quantified by reverse-phase high-pressure liquid chromatography in six patients with end-stage renal disease who were managed by continuous ambulatory peritoneal dialysis. The mean BUN was 61 mg/dl (range, 36 to 79 mg/dl). In uremia, removal of F-AA from the essential amino acid pool to form C-AA is measured by the ratio of C-AA to F-AA (carbamoylation index (CI)). Using the mean value for each essential amino acid, the CIs were as follows: leucine, 4; valine, 3.3; isoleucine, 11.4; threonine, 9; lysine, 2; methionine, 3.5; histidine, 3.5; phenylalanine, 0.5; and tyrosine, 1.3. Carbamoylation of F-AA may account, in part, for the lower than normal levels of F-AA in patients with uremia. The derivatized amino group of C-AA interferes with formation of a peptide bond in protein synthesis, which requires an underivatized amino acid. A decrease in the F-AA pool available for protein synthesis and anabolism in the presence of C-AA may provide additional contributing factors for the development of malnutrition in uremia.

Nutrition impact of peritoneal dialysis solutions.

All peritoneal dialysis (PD) solutions are designed to remove toxins and water, normalize the blood electrolyte profile, and provide alkali to help maintain acid-base balance. Different formulations, however, may have different effects upon nutrition status. Solutions with 40, as opposed to 35, mEq/l of sodium lactate have been found to promote weight and muscle mass gain and reduce hospitalization in malnourished PD patients. Glucose is varied to produce solutions with different ultrafiltration potential. The glucose absorbed from the PD solution has a protein-sparing effect. The high glucose concentrations necessary for sustained ultrafiltration over a long dialysis dwell, however, often produce appetite suppression and metabolic abnormalities. Solutions formulated with glucose polymers, instead of hypertonic glucose, may provide sustained ultrafiltration over long dwells with lower carbohydrate absorption and perhaps fewer metabolic effects. Amino acids can also be substituted for glucose at relatively low concentrations. A number of studies have shown that amino acids absorbed from the dialysis solution can provide nutritional benefit to malnourished PD patients.

Preventing Malnutrition in the Long‐term Peritoneal Dialysis Patient

It is possible to dwell so much on the issue of malnutrition that we overlook the fact that many, if not most, dialysis patients are not malnourished. For this, the hardworking clinicians, nurses, dietitians, industrial scientists and engineers, and the patients and their families deserve praise. Such an achievement would have been unimaginable only a generation ago. Nevertheless, continued improvement of renal replacement therapy requires that we address the needs of the sizable minority of patients who are malnourished. Although the prevalence of malnutrition is about the same in hemodialysis and peritoneal dialysis (PD) patients ( l ) , this review will address protein-calorie malnutrition in long-term PD patients. Malnutrition is the result of an imbalance between nutrient intake and nutrient requirement. The term malnutrition in this review will refer to undernutrition and, specifically, protein-calorie undernutrition. This type of malnutrition may occur as a result of poor intake alone, increased requirements, or an alteration in the utilization of nutrients. All of these conditions may be present in dialysis patients, who often have poor appetite, nutrient losses into dialysate, and an altered milieu which promotes inefficient use of nutrients.