Role of an improvement in acid-base status and nutrition in CAPD patients

Abstract

Short-term correction of metabolic acidosis in normal and uremic subjects has been shown to decrease protein degradation, but the long-term effects of better correction of acidosis on nutrition in ESRF are unknown. The aim of this study was to assess the possible benefits, in the nutritional state and morbidity, of improved correction of acidosis in the first year of treatment with continuous ambulatory peritoneal dialysis (CAPD). Two hundred consecutive new CAPD patients were randomized, in a single-blind fashion, to receive a high (HA; lactate 40 mmol/liter) or low (LA; lactate 35 mmol/liter) alkali dialysate for one year. Calcium carbonate and sodium bicarbonate were also used to correct acidosis in the HA group. At one year, the venous serum bicarbonate and arterial pH were 7.44 +/- 0.004 and 27.2 +/- 0.3 mmol/liter in the HA group, and 23.0 +/- 0.3 mmol/liter and 7.4 +/- 0.004 in the LA group (P < 0.001). Dialysis dose, at one year or at the point of leaving the study (HA 8.0 +/- 0.1 liters/day vs. LA 8.5 +/- 0.3 liters/day) was not significantly different (P = 0.18). At one year, the increase in body weight in the HA group (6.1 +/- 0.66 kg) was higher than in the LA group (3.71 +/- 0.56 kg, P < 0.05). The increase in midarm circumference in the HA patients (1.26 +/- 0.16 cm) was significantly higher than the increase in the LA patients (0.61 +/- 0.16 cm, P < 0.05). The increase in triceps skinfold thickness were not significantly different (HA 2.5 +/- 0.41 mm vs. LA 1.24 +/- 0.38 mm, P = 0.1). Serum albumin was 37.8 +/- 0.4 g/dl at one year in the HA group, and 38.2 +/- 0.5 g/dl in the LA group (NS). Dietary protein intake at one year (HA 0.9 +/- 0.2 g/kg/day vs. LA 1.0 +/- 0.1 g/kg/day) was not significantly different. There were fewer hospital admissions in the HA group (1.13 +/- 0.16 per patient per year) compared to the LA group (1.71 +/- 0.22 per patient per year, P < 0.05). The HA patients spent less days in hospital per year than the LA patients (16.4 +/- 1.4 days/year vs. 21.2 +/- 1.9 days/year; P < 0.05). It is concluded that better correction of metabolic acidosis leads to greater increases in body weight and midarm circumference, but not triceps skinfold thickness, in the first year of CAPD. The improvement in morbidity, in terms of number of admissions and days in hospital per year, may be associated with the improvement in nutritional state.

Oral Sodium Bicarbonate for the Treatment of Metabolic Acidosis in Peritoneal Dialysis Patients

“…Although the effect of oral sodium bicarbonate on appetite has not been reported, Zheng et al (30) recently found that bicarbonate/lactate buffered peritoneal dialysis solutions had a positive effect on appetite. The overall magnitude of benefit observed in our study was similar to a previous report (9), which used high-lactate dialysate for the correction of acidosis. There are, however, controversial opinions about the value of treating mild acidosis in CAPD patients.…”

“…For example, Kang et al (31) reported a better nutritional status in patients with mild metabolic acidosis compared with those without. In the study of Stein et al (9), average hospitalization was 6 d shorter in the treatment group, whereas it was 8 d in our study. It should be noted that the absolute duration of hospital stay was shorter in our patients (e.g., 16 (2).…”

“…Although correction of acidosis by highlactate dialysate improved the nutritional status and reduced the hospitalization of CAPD patients (9), extensive use of a high-lactate dialysate resulted in alkalosis in some patients (10), and the lactate concentration in dialysate cannot be adjusted according to need. Theoretically, oral sodium bicarbonate is a convenient alternative because the dosage can be easily tailored.…”

Exercise-induced Biochemical Modifications in Muscle in Chronic Kidney Disease: Occult Acidosis as a Potential Factor Limiting the Anabolic Effect of Exercise

“…In rats with normal renal function which were subjected to a level of dietary acid loading which failed to alter blood pH, significant acidification of the tissue interstitial fluid was observed even in the renal cortex, in spite of the animals' normal capacity for renal acid excretion 8 . It should also be noted that previous reports of beneficial effects of alkali therapy in peritoneal dialysis patients, for example the study by Stein and coworkers 9 , occurred without substantial increases in arterial blood pH, presumably reflecting functional effects confined to the tissue interstitial fluid. While some 10 but not all studies using micro-dialysis probes in healthy humans have found acidification of skeletal muscle interstitial fluid following muscle contraction in the absence of imposed systemic acidosis; it has also been shown that the fall in the pH of dog muscle interstitial fluid is particularly large during muscle contraction when this is superimposed on a background of pre-existing systemic metabolic acidosis 11 , the acidification effects of the systemic acidosis and of the lactic acid generated being more than additive.…”

Effects of Oral Sodium Bicarbonate in Patients with CKD

“…Notably, this pathway mediates the anabolic and anticatabolic effects of IGF-1 and insulin (10), implicating acidosis as one cause of the resistance to both hormones seen in uremia (6,8). In humans with advanced CKD, treatment of severe acidosis has produced improvements in anthropometric measures of lean body mass in some (2,11,12) but not all (13)(14)(15) reports.…”