Bradley J. Maroni

Factors causing malnutrition in patients with chronic uremia

There is abundant evidence that patients with chronic renal failure (CRF), including those treated by hemodialysis or peritoneal dialysis, have evidence of malnutrition with decreased body weight and subnormal values of serum proteins (suggesting a loss of visceral protein stores). Potential causes of an abnormal nutritional status that have been identified include an inadequate intake of protein or calories, an inability to activate the metabolic responses that are needed to achieve nitrogen and protein balance, or the presence of a disease that prevents activation of these metabolic responses or acts to stimulate the breakdown of body protein stores. Three critical metabolic responses to a limited protein intake have been identified: a reduction in the irreversible degradation of amino acids and the degradation of protein breakdown and an increase in protein synthesis in response to a meal. Metabolic acidosis blocks the first two responses and hence contributes to malnutrition in patients with chronic uremia. Other factors that could contribute to malnutrition include an inadequate intake because of anorexia or hormonal imbalances that impair protein turnover. In evaluating CRF patients with malnutrition, the first task is to ensure an adequate intake and to eliminate factors that impair the ability to achieve nitrogen balance.

Nutritional Considerations in the Treatment of Patients with Chronic Uremia

Low-protein diets ameliorate uremic symptoms and some of its metabolic complications. These diets can be used successfully to treat patients with chronic renal failure (CRF) because they are able to activate normal compensatory responses when protein intake is restricted and their protein and energy requirements are similar to healthy subjects. However, there has been concern that dietary therapy compromises the nutritional status of CRF patients and that initiating dialysis would be preferable to this type of therapy. Kopple and co-workers hade identified the requirements of CRF patients for protein and calories and available evidence indicates that when properly implemented, low-protein diets are safe and can maintain lean body mass even during long-term therapy. Based on the information published by Kopple and co-workers, the strategies for treating CRF patients should include careful analysis of the diet and the nutritional status of the patient.

Impact of Chronic Renal Failure on Nitrogen Metabolism

Evidence indicates that both nephrotic and nonnephrotic chronic renal failure (CRF) patients can activate normal compensatory responses when dietary protein intake is restricted and that their protein and energy requirements are similar to normal subjects. When properly implemented, low-protein diets are safe and the benefits include the amelioration of uremic symptoms and some of their metabolic complications and possibly a reduction in the rate of progression of renal failure. To ensure dietary adequacy and compliance, patients should be monitored when treated with low-protein diets. Recent evidence that the protein intake of patients with progressive CRF declines when they consume unrestricted diets should not be considered as an argument against the use of low-protein diets. Rather, it is a persuasive argument in favor of restricting dietary protein intake to minimize the complications of renal failure.

What are the Important Considerations in the Care of Critically III Patients with Acute Renal Failure

With the recent progress in molecular and cellular biology, the 1990s present a unique opportunity for understanding the cellular or humoral factors responsible for accelerated catabolism in ARF. This author believes that a greater priority should be placed on funding basic research directed at understanding the pathogenesis of protein catabolism in ARF. For example, identifying the intracellular pro‐teolytic pathways which are activated in experiment& ARF might lead to strategies to suppress accelerated proteolysis. Insight gained from these efforts could then be used to design clinical trials to test the efficacy of nutritional interventions in this patient population. In this era of increased economic constraints, practical solutions to this formidable problem are needed.