Metabolic balance studies and dietary protein requirements in patients undergoing continuous ambulatory peritoneal dialysis

Metabolic balance studies and dietary protein requirements in patients undergoing continuous ambulatory peritoneal dialysis. Balance studies for nitrogen, potassium, magnesium, phosphorus, and calcium were carried out in eight men undergoing continuous ambulatory peritoneal dialysis (CAPD) to determine dietary protein requirements and mineral balances. Patients were fed high energy diets for 14 to 33 days which provided either 0.98 (seven studies) or 1.44g (six studies) of primarily high biological value protein/kg body wt/day. Mean nitrogen balance was neutral with the lower protein diet (+0.35 ± 0.83SEMg/day) and strongly positive with the higher protein diet (+2.94 ± 0.54g/day). With the higher protein diet the balances for potassium, magnesium, and phosphorus were strikingly positive, there was an increase in body weight in all patients, and a rise in mid-arm muscle circumference in five of the six patients. The relation between protein intake and nitrogen balance suggests that the daily protein requirement for clinically stable CAPD patients should be at least 1.1g/kg/day; to account for variability among subjects 1.2 to 1.3g protein/kg/day is probably preferable. Potassium balance correlated directly with nitrogen balance (r = 0.81). High fecal potassium losses (19 ± 1.2 mEq/day) in all patients probably helped maintain normal serum potassium concentrations. Mean serum magnesium was increased (3.1 ± 0.1 mg/dl), and magnesium balances were positive suggesting that the dialysate magnesium of 1.85 mg/dl is excessive. The netgain of calcium from dialysate was 84 ± 18 mg/day; this correlated inversely with serum calcium levels (r = -0.90). Bilans metaboliques et besoins proteiques alimentaires de malades en dialyse peritoneale continue ambulatoire. Des etudes de bilan de l'azote, du potassium, du magnesium, du phosphore et du calcium, etaient fait en sept hommes en dialyse peritoneale continue ambulatoire (CAPD), pour determiner leurs besoins proteiques alimentaires et leur bilan mineral. Les malades ont recu pendant 14 a 33 jours des regimes hautement energetiques, apportant soit 0,98 (sept etudes), soit 1,44g (six etudes) de proteines de haute valeur biologique par kg de poids et par jour. Le bilan azote moyen etait nul avec le regime comportant la plus faibie teneur proteique (+ 0,35 ± 0,88g/jSEM) et etait fortement positive avec le regime a plus forte teneur proteique (+2,94 ± 0,54g/j). Avec le regime a haute teneur en proteine, les bilans potassique, magnesien et phosphore etaient fortement positifs; le poids corporel s'est eleve chez tous les malades; la circonference musculaire mesuree du milieu du bras a augmente chez cinq sur six malades. La relation existant entre l'apport proteique et le bilan azote suggere que les besoins journaliers en proteines pour des malades cliniquement stables en CAPD devraient etre au moins de 1,1g/kg/j; 1,2 a 1,3g de proteines/kg/j sont sans doute preferables pour tenir compte de la variabilite entre les sujets. Le bilan potassique etait directement correle avec la balance azotee (r = 0,81). De fortes pertes potassiques fecales (19 ± 1,2 mEq/j) chez tous les malades ont probablement contribue a maintenir normales les concentrations seriques du potassium. La magnesemie moyenne etait elevee (3,1 ± 0,1 mg/dl), et les bilans magnesiens aient positifs suggerant que le magnesium du dialysat (1,85 18 mg/dl) etait trop eleve. Le gain net en calcium a partir du dialysat etait de 84 ± 18 mg/j; ce gain etait inversement correle avec la calcemie (r = 0,90).