Nutrition and Mortality in Hemodialysis1
Total Page:16
File Type:pdf, Size:1020Kb
Nutrition and Mortality in Hemodialysis1 Jonas Bergstrom2 sufficiently well proved. More and better data, gener- J. Bergstrom, Deparlment of Renal Medicine and Bax- ated in prospective, well-controlled studies, are obvi- ter Novum, Karolinska Institute, Huddinge University ously needed before intradialyfic parenteral nutrition Hospital, Stockholm, Sweden can be generally recommended as therapy for mal- (J. Am. Soc. Nephrol. 1995; 6:1329-1341) nourished HD patients. Key Words: Albumin. anorexia. cachexia. catabolism, malnu- fri/Ion ABSTRACT Protein-energy malnutrition is present in a large pro- I 960, Scribner et at. ( 1 ), in their first report on portion of maintenance hemodialysis (HD) patients, hemodialysis (HD) treatment of patients with and it is associated with increased morbidity and chronic renal failure, pointed out that malnutrition mortality. The protein requirements are increased be- may be a serious problem. Numerous studies pub- cause of the presence of endocrine and metabolic lished thereafter have demonstrated a high prevalence factors related to loss of renal function, the HD proce- of malnutrition in HD patients. In more recent years, dure, and comorbidity factors, which all stimulate net several reports have focused on the association be- tween nutritional Intake and nutritional status, on the protein catabolism. The intake protein and energy one hand, and morbidity and mortality on the other, are frequently reduced because of the underlying lending support to the supposition that nutritional disease, psychosocial factors, and uremic anorexia. inadequacies may be causally related to a fatal out- However, the extent to which underdialysis contrib- come. However, the role of nutrition In this regard has utes to anorexia and malnutrition is still not well de- not been clearly determined. Several morbidity factors fined. Malnutrition is generally not recognized as a that per se increase the risks of a poor outcome may common direct cause of death as reflected in health also cause malnutrition, which may not be the direct statistics, except in the highest age groups. Anthropo- cause of death, but rather a marker of illness. metric and biochemical signs of malnutrition are There are many causes of malnutrition in renal associated with increased mortality. A low serum failure patients who are treated with HD, some being related to endocrine and metabolic disturbances of albumin level is a strong predictive risk factor that uremia and some being related to the dialytic proce- may reflect not only or mainly protein malnutrition but dure. A controversial issue is the extent to which the also the influence of several other morbidity factors adequacy of dialysis may affect the nutritional intake (overhydration, infection, chronic disease and oth- of protein (and energy), especially If there exists a link ers) that may entail an increased risk of death. Low between underdialysis, malnutrition, and increased levels of serum creatinine (low muscle mass), serum morbidity/mortality. cholesterol (energy depletion), and BUN and low urea appearance rate (low protein intake) are also GENERAL ASPECTS OF NUTRITION AND correlated to increased mortality. For the prevention MORTALITY and treatment of HD-associated malnutrition, mea- In order for an individual to survive and thrive, sures should be taken to correct factors that may nutrients must be ingested in sufficient amounts to suppress appetite and increase net protein catabo- serve as metabolic fuel and a substitute for tissue lism (underdialysis, acidosis, low energy intake, co- growth and maintenance and to regulate the cellular morbid conditions, psychosocial and economic fac- and metabolic processes. If an essential nutrient (e.g., tors). Dietary advice should be given with the aim of a specific amino acid or a vitamin) or a macronutrient ensuring an adequate intake of protein- and energy- (protein, energy) is provided in insufficient amounts In giving products. Intradialyfic parenteral nutrition may relation to the requirements, this will sooner or later have positive effects on nutritional status when other have serious consequences for the Individual. How- measures fail. However, the indications for such treat- ever, a nutritional deficiency may be clinically unrec- ognizable for some time and may be detected only by ment have not yet been well defined, and the effects biochemical and physiologic studies or by metabolic on survival, morbidity, and quality of life are not experiments. As the deficiency becomes more severe, the altered biologic and physiologic functions in the 1 Received January 19. 1995. Accepted June 21. 1995. body and clinical signs and symptoms occur, leading 2 correspondence to Dr. J. Bergstrom, Department of Renal Medicine K56, to morbidity and, finally, the death of the subject (2). Huddinge University Hospital, 5-14186 Huddinge. Sweden. Only then is the consequence of malnutrition reflected 104&6673/0605-1 329$03.00/0 in vital statistics. It should be emphasized that even Journal of the American Society of Nephrology copyright © 1995 by the American Society of Nephroiogy less severe deficiencies may (Indirectly) have a nega- Journal of the American Society of Nephrology 1329 Nutrition and Mortality in HD tive effect by sensitizing the individual to other morbid because it measures both the bone mineral content factors. For instance, protein malnutrition may result and the body fat mass, measurements from which the in an impaired immune response, carrying an in- lean body mass is calculated. The lean body mass, as creased risk of severe or even fatal infections (3). The calculated by DEXA or by total body water determina- regeneration of cell number and function, e.g. , after tion (by monofrequency bioimpedance or isotope dilu- an acute illness, and wound healing may also be tion or from nomograms) is, by definition, equal to the impaired in states of malnutrition (4). body weight minus the amount of body fat. Therefore, it is not a reliable index of total cell mass (body ASSESSMENT OF PROTEIN-ENERGY MALNUTRITION protein) in overhydrated dialysis patients, whose lean body mass consists largely of excess water, mainly in To diagnose malnutrition in maintenance dialysis the extracellular space ( 1 2). Multifrequency bioimped- patients, it is important to assess correctly their nu- ance may turn out to be more useful by enabling tritional status (see recent review articles [5,6]). The compensation for extracellular overhydration in the validation of nutritional status may be based on din- calculation of body cell mass. Creatinine is generated ical evaluation, diet history, anthropometric measure- largely by the nonenzymatic breakdown of creatine ments, and various biophysical and biochemical present in the phosphocreatine-creatine pool in skel- methods (Table 1). etal muscle, which is the largest pool of cellular tissue The more precise methods for calculating body com- in the body ( 13). In addition, 10 to 30% of creatmnine position (total water, potassium and nitrogen determi- generation may be derived from the ingestion of crea- nations, protein/DNA determination in muscle bi- tine and creatinine in meat ( 1 4). Potassium, alkali- opsy, dual x-ray photon absorptiometry [DEXA], soluble (cell) protein, and total creatine in the skeletal nuclear magnetic resonance, bioelectrical impedance, muscle of normal individuals are strongly correlated etc.) require equipment that is not available in most ( 15). The total creatinine output has been shown to centers, some of which is complicated and expensive. correlate well with the total body K in normal and Among the new noninvasive methods, DEXA (7) and continuous ambulatory peritoneal dialysis (CAPD) pa- multifrequency bioimpedance (which can distinguish tients, and it may be a more reliable index ofbody cell between total body water and extracellular water) (8) mass and nutritional status in dialysis patients than are now under evaluation for use in patients on main- the techniques that are based on total water determi- tenance dialysis (9-1 1 ). DEXA may be advantageous nations ( 16). However, the determination of the total creatine output in HD patients requires the collection TABLE 1. Methods to assess nutrition used in HD of an aliquot of the total spent dialysate during the patients dialysis session, which is not easily accomplished. Today, most centers must rely on dietary histories, Evaluation of Nutritional Intake evaluation of body weight indices, and other simple Dietary history and dietary records anthropometric parameters and serum protein deter- Urea appearance (estimation of protein intake) minations to investigate nutritional status and detect Simple Anthropometric Methods signs of protein-energy malnutrition. A simple and Body weight, body mass index, weight loss reliable method appears to be the Subjective Global Skinfold thickness (triceps and other sites) Assessment, a technique by which the nutritional Midarm muscle circumference status is rated by the clinician in a systematic way Muscle strength (handgrip) Body Composition based on medical history and physical examination DEXA ( 1 7). Although originally used to classify surgical pa- Nuclear magnetic resonance tients, this nutritional classification system has Computed tomography proved to be a reliable tool for assessing the nutri- Ultrasonography tional status of dialysis patients ( 1 8, 19). Bloelectrical impedance Total body H20 (isotope dilution), K (40K-count), N PREVALENCE OF MALNUTRITION IN HD PATIENTS (neutron activation