Controlled comparison of hemodialysis and peritoneal dialysis: Veterans Administration multicenter study.

We measured mortality and morbidity among 114 patients assigned randomly to home hemodialysis (HD) and home intermittent peritoneal dialysis (IPD). Data were collected during the time of home training and for 12 months after initiation of home dialysis. Training time was shorter for the IPD than for the HD patients (P less than 0.001) with median time 1.8 months for IPD and 3.9 months for HD. Switching to the alternative mode of treatment was more frequent for the IPD group (29/59 vs. 5/55, P less than 0.001). Survival time was not different, perhaps because of the modality change. More IPD patients were hospitalized in the first 6 months (20 for IPD vs. 9 for HD, P = 0.02), but they had fewer troublesome cardiovascular events in the first year (0 vs. 12, P less than 0.001). The HD patients maintained better nutritional status as reflected in body weight and arm muscle circumference and possibly in urea appearance rate. Thus, these data suggest that for most patients, IPD is a less satisfactory form of therapy than HD, but certain advantages of IPD did emerge. Applications of this information to the currently more popular mode of CAPD await further study.

Nutritional requirements for patients undergoing continuous ambulatory peritoneal dialysis.

Recent studies suggest that patients undergoing continuous ambulatory peritoneal dialysis (CAPD) may be prone to develop protein depletion. This paper reviews data concerning glucose uptake, protein and amino acid losses, and nitrogen and mineral balances in clinically stable adult CAPD patients. Approximately 70% of the glucose instilled with dialysate was absorbed, and the glucose absorbed provided approximately 8 kcal/kg/day to the patient. Serum total protein and albumin losses into dialysate averaged 8.8 +/- (SEM) 0.5 and 5.7 +/- 0.4 g/day, respectively. The quantity of free amino acids removed with dialysis was less, 3.4 +/- 0.3 g/day. The balance studies suggest that a safe dietary protein allowance for clinically stable CAPD patients who are ingesting high energy diets is 1.2 to 1.3 g/kg/day. Tentative dietary allowances for other nutrients in clinically stable CAPD patients are proposed.

Nutritional status of children undergoing continuous ambulatory peritoneal dialysis.

Nutritional status was assessed in 24 clinically stable children, aged 9.68 +/- 4.31 (SD) yr, who underwent CAPD for 6.6 +/- 4.4 months. Energy intake tended to be more suppressed than protein intake. Several nutritional parameters were more abnormal in children less than 10 yr old as compared to children 10 yr of age or older. In comparison to normals of the same chronological age and sex, both groups of patients displayed reduced height, weight, midarm, and midarm muscle circumference, and, in the younger children, triceps skinfold; height retardation was particularly severe. Compared to height/age, anthropometry was not reduced in older children while triceps skinfold and midarm circumference were decreased in children younger than 10 yr. In both groups, serum total protein, albumin, transferrin, and many plasma amino acids were decreased, and serum triglycerides and cholesterol were elevated. Serum total protein decreased during treatment with continuous ambulatory peritoneal dialysis. These observations suggest decreased stature and poor nutritional status in children undergoing continuous ambulatory peritoneal dialysis. Low protein and energy intake and dialysate protein losses may contribute to these abnormalities.

Plasma amino acid levels and amino acid losses during continuous ambulatory peritoneal dialysis.

Free amino acid losses into dialysate during a 24-h collection period and postabsorptive plasma amino acid concentrations were measured in 14 studies in nine clinically stable men undergoing continuous ambulatory peritoneal dialysis. Patients ingested diets containing 97 +/- 18 (SD) g/day of protein in a metabolic research unit. Total amino acid losses were 3.4 +/- 1.2 g/24 h and represented 3.9 +/- 1.9% ot total nitrogen output (in dialysate, urine and feces). The sum of plasma essential, nonessential, and total amino acid concentrations was normal, although plasma valine, leucine, and isoleucine were decreased and several amino acids were elevated. Neither plasma nor dialysate amino acids, varied with protein intake. Dialysate amino acid concentrations averaged 72 +/- 18% of plasma levels, and 29.0 +/- 3.6% of dialysate amino acids were essential. Dialysate concentrations and 24 h losses of individual amino acids each correlated with plasma levels (r = 0.83 and 0.78, respectively). Thus during continuous ambulatory peritoneal dialysis, postabsorptive plasma amino acids are, in general, well maintained. Daily losses of free amino acids during continuous ambulatory peritoneal dialysis are rather small and are easily replaced by food intake.

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 1.44 g (six studies) of primarily high biological value protein/kg body wt/day. Mean nitrogen balance was neutral with the lower protein diet (+0.35 +/- 0.83 SEM g/day) and strongly positive with the higher protein diet (+2.94 +/- 0.54 g/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 1.1 g/kg/day; to account for variability among subjects 1.2 to 1.3 g 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 net gain of calcium from dialysate was 84 +/- 18 mg/day; this correlated inversely with serum calcium levels (r = -0.90).

Nitrogen and urea metabolism during continuous ambulatory peritoneal dialysis.

During continuous ambulatory peritoneal dialysis (CAPD), concentrations of serum urea nitrogen (SUN) have been reported that are lower than what would be predicted from estimated dietary protein intake and the calculated urea clearance by dialysis. Net urea generation (urea nitrogen appearance) and losses of various nitrogenous constituents were measured during 12 metabolic studies in patients undergoing CAPD. Patients ingested constant diets containing either 1.0 or 1.4 g or protein per kilogram of body wt per day; total daily urea "clearance" from peritoneal dialysis plus renal clearance averaged 10.8 +/- 0.3 liters/day. Urea nitrogen appearance was only 55 and 68% of total nitrogen output with the low and high protein diets, respectively, values that are substantially lower than those reported in normal subjects, patients with chronic renal failure, and those undergoing hemodialysis. The reduction fraction of nitrogen appearing as urea was largely accounted for by the loss of protein and free amino acids into the dialysate. These respective constituents accounted fro 11.5 and 4.4% of total nitrogen output. Urea nitrogen appearance correlated closely (r = 0.96) with total nitrogen output in the patients undergoing CAPD.

Daily requirement for pyridoxine supplements in chronic renal failure.

Vitamin B6 deficiency was evaluated in 37 patients with chronic renal failure and in 71 patients undergoing maintenance hemodialysis (HD) or intermittent peritoneal dialysis (PD). Vitamin B6 deficiency was assessed by the in vitro activity of erythrocyte glutamic pyruvic transaminase (EGPT), without (basal) and with (stimulated) the addition of pyridoxal-5-phosphate to the assay, and the EGPT index (stimulated activity ./. basal activity). Basal and stimulated EGPT activities were below normal in the HD patients, and the EGPT index was increased in each group of patients, indicating vitamin B6 deficiency. Supplemental pyridoxine hydrochloride was given to 30 HD patients who received 1.25 to 50 mg/day (37 studies), 6 PD patients who were given 1.25 or 2.5 mg/day (7 studies), and 8 nondialyzed patients with mild to severe renal failure who received 2.5 mg/ day. In all HD patients, 10 or 50 mg/day of pyridoxine hydrochloride rapidly corrected the abnormal EGPT index and maintained normal values; with supplements of 5.0 mg/day or less, the index was often abnormal, particularly in those who were septic or taking pyridoxine antagonists. In PD patients and nondialyzed patients with renal failure, 2.5 mg/day of pyridoxine hydrochloride was inadequate to correct rapidly the abnormal index in all patients. These findings suggest that HD patients should receive 10 mg/day of supplemental pyridoxine hydrochloride (8.2 mg/day pyridoxine). PD patients and patients with chronic renal failure should receive about 5.0 mg/day of supplemental pyridoxine hydrochloride (4.1 mg/day pyridoxine). When sepsis intervenes or vitamin B6 antagonists are taken, 10 mg/day of pyridoxine hydrochloride may be a safer supplement for all patients.

Retrograde menstruation in women undergoing chronic peritoneal dialysis.

Blood in the peritoneal dialysis catheter just before menstruation was regularly observed in 9 of 11 premenopausal women maintained on peritoneal dialysis for end-stage renal failure. Peritoneal bleeding at other times during the menstrual cycle was not seen in any of these patients. Likewise, peritoneal bleeding in men or nonmenstruating women on chronic peritoneal dialysis was exceedingly rare, was not periodic, and usually was due to recognizable causes. These observations suggest that retrograde menstrual bleeding into the peritoneal cavity is the rule rather than the exception in women on peritoneal dialysis and possibly in all menstruating women. Implications of this observation for the pathogenesis of endometriosis and dysmenorrhea are discussed.

Glucose absorption during continuous ambulatory peritoneal dialysis.

Patients undergoing continuous ambulatory peritoneal dialysis (CAPD) are exposed to a continuous infusion of glucose via their peritoneal cavity. We performed studies to quantitate the amount of energy derived from dialysate glucose. Net glucose absorption averaged 182 +/- (SD) 61 g/day in 19 studies with a dialysate dextrose concentration of 1.5 or 4.25 g/dl. The amount of glucose absorbed per liter of dialysate (y) varied with the concentration of glucose in dialysate (x), (y = 11.3x - 10.9, r = 0.96). The amount of glucose absorbed per day during a given dialysis regimen was constant. Energy intake from dialysate glucose was 8.4 +/- 2.8 kcal/kg of body wt per day, or 12 to 34% of total energy intake. This additional energy may contribute to the anabolic effect reported during CAPD. The ability to vary glucose absorption by altering the dialysate glucose concentration may prove a useful tool to modify energy intake.

Protein losses during peritoneal dialysis.

The losses of protein into dialysate have been considered a major limitation of maintenance peritoneal dialysis. We, therefore, undertook a comprehensive evaluation of protein losses in 30 patients undergoing maintenance intermittent peritoneal dialysis (IPD), 12 patients undergoing acute IPD, and 8 patients undergoing continuous ambulatory peritoneal dialysis (CAPD). The weekly loss of protein based upon the usual treatments per week was relatively similar with the three modes of dialysis. Protein losses during repeated dialyses were similar for a given patient, but there was repeated dialyses were similar for a given patient, but there was marked interpatient variation. During maintenance IPD, protein loss was 12.9 +/- (SD) 4.4 g per 10 hours of dialysis; albumin loss was 8.5 g, and IgG loss was 1.3 g. Approximately 50% of the protein loss was from the ascitic fluid accumulated during the interdialytic interval, and concentrations of most proteins in the ascitic fluid correlated with their serum levels. Serum protein concentrations were in the low, normal range and did not change during dialysis. The development of peritonitis markedly increased protein losses. During acute IPD, 23.3 +/- 16.5 g of protein were lost per 36 hours of dialysis, lower losses than those previously reported. With CAPD, 8.8 +/- 1.7 g of protein were removed per 24 hours; also immunoglobulin losses correlated with their serum concentrations. The results of these studies suggest that, in the absence of peritonitis, dialysate protein losses do not appear to limit the usefulness of peritoneal dialysis.

Clinical and metabolic responses to parenteral nutrition in acute renal failure. A controlled double-blind study.

1. Thirty patients with acute renal failure who were unable to eat adequately were evaluated while they received parenteral nutrition with glucose alone (n = 7), glucose and 21 g/day essential amino acids (EAA, n = 11) or glucose, 21 g/day essential and 21 g/day nonessential amino acids (ENAA, n = 12). Energy intake did not differ with the three treatments. Patients were studied in a prospective double blind fashion. 2. Thirteen patients recovered renal function and 11 survived to leave the hospital. Those in whom renal failure was attributed to hypotension and/or sepsis had a poorer recovery of renal function (17%) and survival (17%). Recovery of renal function and survival was greater in patients on the medical service as compared to the surgical service and in those who received more energy. Recovery of renal function was worse in those treated with dialysis. There were no differences in recovery of renal function of survival among the three treatment groups. 3. Many patients were markedly catabolic as indicated by nitrogen balances, urea in nitrogen appearance rates (UNA), serum protein concentrations, and plasma amino acid levels. There was no correlation between the degree of catabolism and recovery of renal function or survival. Mean UNA in individual patients also correlated with body weight. Among the three groups, however, UNA was significantly less with the group receiving EAA as compared to ENAA. 4. Serum protein concentrations were lower than normal in all treatment groups. Serum albumin fell significantly during the treatment in the more catabolic patients. Plasma amino acid levels tended to fall in all three groups and concentrations at the end of the treatment were frequently lower than normal. 5. These data suggest that acute renal failure patients who are unable to eat adequately are often hypercatabolic and have a high mortality, particularly if hypotension or sepsis is the cause of renal failure. The improved survival in those with higher energy intakes, the high rate of net protein breakdown, the low serum protein levels and the reduced plasma concentrations of both essential and nonessential amino acids suggest that greater quantities of energy and both essential and nonessential amino acids may be beneficial to such patients.

Nutritional and metabolic response to catabolic stress in uremia.

Metabolic balance studies were conducted in five nondialyzed chronically uremic patients and four patients undergoing maintenance hemodialysis or peritoneal dialysis who had sustained an acute intercurrent illness. Nitrogen balance became negative in all patients. In eight patients who did not have marked fluid removal, serum total protein, albumin and transferrin fell significantly. Negative nitrogen balance was caused by three factors: 1) decreased nitrogen intake, which wasn't always readily apparent 2) increased urea nitrogen appearance, and 3) in peritoneal dialysis patients with peritonitis, protein losses into dialysate. In the chronically uremic patients, urea nitrogen appearance correlated closely with total nitrogen output and appears to be a good predictor of total nitrogen losses.

Methods for assessing nutritional status of patients with renal failure.

Since wasting and malnutrition are common problems in patients with renal failure, it is important to develop techniques for the longitudinal assessment of nutritional status. This paper reviews available methods for assessing the nutritional status; their possible limitations when applied to uremic patients are discussed. If carefully done, dietary intake can be estimated by recall interviews augmented with dietary diaries. Also, in a stable patient with chronic renal failure, the serum urea nitrogen (N)/creatinine ratio and the rate of urea N appearance reflect dietary protein intake. A comparison of N intake and urea N appearance will give an estimate of N balance. Anthropometric parameters such as the relationship between height and weight, thickness of subcutaneous skinfolds, and midarm muscle circumference are simple methods for evaluating body composition. Other methods for assessing body composition, such as densitometry and total body potassium, may not be readily applicable in patients with renal failure. More traditional biochemical estimates of nutritional status such as serum protein, albumin, transferrin, and selected serum complement determinations show that abnormalities are common among uremic patients. Certain anthropometric and biochemical measurements of nutritional status are abnormal in chronically uremic patients who appear to be particularly robust; thus, factors other than altered nutritional intake may lead to abnormal parameters in such patients. Serial monitoring of selected nutritional parameters in the same individual may improve the sensitivity of these measurements to detect changes. Standards for measuring nutritional status are needed for patients with renal failure so that realistic goals can be established optimal body nutriture.

Nutritional assessment and treatment of chronic renal failure.

The experience with chronic renal failure in two institutions, a tertiary care referral hospital with a high prevalence of diabetes mellitus and a Veterans Administration Hospital, was utilized to formulate guidelines for the nutritional assessment and therapy of chronic renal failure. For optimal nutritional support of patients with renal failure, it is important to characterize objectively nutritional deficiencies. Thus, dietary history, anthropometric measurements (weight/height ratio, arm muscle circumference, and triceps skinfold), and serum protein measurements (total protein, albumin, and transferrin, in particular) provide valuable data concerning the nutritional status of the patient. The serum urea nitrogen to serum creatinine ratio and urea nitrogen appearance are useful for selecting optimal protein intake. The serum urea nitrogen/creatinine ratio must be interpreted with respect to the factors which influence it; i.e., the urea clearance and the urea nitrogen appearance. The goal of nutritional therapy is the preservation of body cell mass and function, fluid, electrolyte, and acid-base homeostasis, mineral balances, and with early use of dialysis, the avoidance of uremic toxicity. Nutritional therapy, especially in patients with superimposed illnesses and associated anorexia, may be enhanced by the use of formula feedings, tube feedings, and, if necessary, total parenteral nutrition.

Applications of the Redy sorbent system to hemodialysis and peritoneal dialysis.

The application of sorbent technology to the treatment of uremia has been limited by the inability to adsorb urea adequately. Conversion of urea to ammonium carbonate and adsorption by zirconium phosphate provides a practical means of removing urea. This combination, together with hydrated zirconium oxide and carbon, removes uremic waste products from dialysate. Over 1500 patients are undergoing maintenance hemodialysis with this system. The dialysate composition can be modified for the treatment of patients with acute renal failure. This sorbent system is now being used for the regeneration of peritoneal dialysate. Twenty patients have undergone a total of 90 dialyses, each of 4 to 24 hours duration. One home patient has been solely on this system for two months. The application of sorbent technology to peritoneal dialysis may be the most promising approach to a wearable dialysis system.