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EDITORIAL |
1 From the Department of Gastroenterology and Hepatology, University Medical Center Nijmegen, Nijmegen, Netherlands.
2 Address reprint requests to THJ Naber, Department of Gastroenterology and Hepatology, University Medical Center Nijmegen, PO Box 9101, 6500 HB Nijmegen, Netherlands. E-mail: t.naber{at}mdl.umcn.nl.
See corresponding article on page 613.
Malnutrition is a frequent problem in hospitalized patients. In 1936 Studley (1) observed a higher mortality rate in malnourished than in well-nourished patients after elective surgery for peptic ulcer disease. This association suggests a causal correlation between malnutrition and clinical outcome. Subsequently, the goal was formulated to strive for optimal nutritional status in the perioperative period on the basis that the complication rate and mortality rate would improve as a result of nutritional intervention. Whereas many studies have been performed to prove this hypothesis, most studies have been disappointing, possibly because in most cases the patients were not stratified according to their nutritional status. The Veteran Affairs Study Group showed that only severely malnourished patients benefited from nutritional intervention before surgery (2). Because of this observation, nutritional support became part of the standard treatment of malnourished surgical patients.
Other investigators showed higher complication rates in malnourished nonsurgical patients than in well-nourished nonsurgical patients (3). These observations provided the impetus for the development of methods and indexes to define nutritional status in hospitalized patients. However, most indexes are complex, difficult to calculate, often not applicable to clinical practice, and influenced by the underlying disease. For example, weight loss is a simple method for the assessment of nutritional status in patients (1, 4), but it is influenced by factors other than nutritional status, such as overhydration and dehydration.
The article by Pichard et al (5) in this issue of the Journal shows a clear association between fat-free mass, as assessed by bioelectric impedance analysis (BIA), and the length of hospital stay (LOS). Fat-free mass correlates with skeletal muscle mass (6), and improvement of muscle mass by nutritional intervention together with physical training may improve the clinical course of disease (7). Whereas nitrogen balance has been used to determine the effects of nutritional intervention on protein mass, it does not provide information about the process of protein breakdown and protein synthesis (8). Currently, protein metabolism can be assessed by more sophisticated and sensitive methods, such as the use of stable isotopes to evaluate protein breakdown and synthesis. The influence of nutritional intervention on protein metabolism can now be studied in detail and is relevant because a decrease in fat-free mass is associated with a longer LOS.
Although the present study is important, it has its limitations. BIA was used to assess fat-free mass, but fat-free mass is also influenced by fluid balance. In the current study, this limitation was overcome, in part, by the exclusion of patients with edema or burns or who had undergone hemodialysis, rehydration perfusion, or cardiorespiratory resuscitation. However, these exclusions limited the relevance of the study because patients with these symptoms or complications are especially at risk of malnutrition and a long LOS. Other relevant endpoints, such as disease complications and the physical capacities of the patients, were not assessed. Although mortality was low in the current study, its association with fat-free mass could not be determined because the most severely ill patients were excluded. Low serum albumin was associated with a low fat-free-mass index in men. Serum albumin is strongly influenced by the inflammatory response in patients. More direct indicators of the inflammatory response in these patients, such as C-reactive protein concentrations, were not mentioned. The decrease in fat mass is probably caused by the catabolic effect of the disease, which is difficult to treat by nutritional intervention. According to the authors, nutritional interventions were not mentioned and are not relevant because nutritional status was assessed only at admission. However, nutrition interventions are relevant because these interventions may influence LOS by introducing complications or causing a positive effect on the course of the disease. LOS is influenced by many factors besides nutritional status. It is important to have detailed information about other factors that influence LOS, such as disease categories and the percentage of patients admitted to the intensive care unit; however, this information was not provided in sufficient detail in the article by Pichard et al.
Pichard et al suggest that lean body mass be determined in every hospitalized patient by using a simple method such as BIA. A low fat-free-mass index better predicts a longer LOS than does body mass index or a Subjective Global Assessment questionnaire. Should BIA be used routinely for the assessment of nutritional status in patients at the time of admission to a hospital? The information provided in the article by Pichard et al is too limited to recommend this practice as a routine method: ie, severely ill patients were excluded, the patient population was not well described, complications secondary to the disease and observed during the hospital stay together with other clinically relevant endpoints were not addressed, and confounding factors that influence LOS were not mentioned. BIA is not applicable as a screening tool for malnutrition or the risk of malnutrition in patients because it does not depict the group of patients who are at risk of malnutrition but are not yet malnourished. The relevance of BIA in clinical nutritional intervention trials needs to be established.
The importance of the study by Pichard et al is that it shows that a decrease in lean body mass is associated with a longer LOS. The past is the future: the study by Pichard et al may renew interest in the assessment and improvement of protein mass and protein metabolism in clinical studies because it suggests an association with the clinically relevant endpoint LOS. Lean body mass, as an indicator of malnutrition or as a screening instrument for determining the course of a disease, should be studied in more detail before its measurement can be introduced as a routine method for evaluating the nutritional status of patients.
REFERENCES
Related articles in AJCN:
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