Correspondence
Predictors of Mortality in Patients Undergoing Hemodialysis
N Engl J Med 1994; 330:573-574February 24, 1994
- Article
To the Editor:
Owen et al. (Sept. 30 issue)1 found that lower serum albumin concentrations were associated with an increased risk of death in patients with end-stage renal disease who were undergoing hemodialysis and concluded that poor nutrition was a major factor contributing to this increased mortality. We question this conclusion.
Serum albumin is often measured as part of a nutritional assessment, but as the authors noted, low serum albumin concentrations may be caused by many conditions other than malnutrition. In patients with inflammation, infection, or injury the catabolism and extravasation of albumin may be increased, and its synthesis decreased2. Although adequate nutritional status may minimize the fall in serum albumin, the initial decrease due to injury cannot be prevented. In contrast, serum albumin concentrations are relatively normal in patients with anorexia nervosa or starvation until late in the disease process, despite obvious compromise of nutritional status. Thus, the metabolic response to injury can have a much greater effect on serum albumin than nutritional factors.
In their analyses, Owen et al. did not control for the presence or severity of concurrent illness. Controlling for the primary renal diagnosis is not adequate in this regard. Without adjusting for the severity of illness, it is not possible to conclude or imply that mortality associated with a low serum albumin concentration is a result of nutritional factors in themselves. It may be that a low value is a marker for associated diseases, including subclinical illness, and that these diseases are responsible for the increased mortality.
We certainly agree with the authors that the nutritional status of patients undergoing hemodialysis should be improved. However, the conclusion that inadequate nutrition was responsible for the increased mortality in their study is not supported by their data.
2 ReferencesDonald D. Hensrud, M.D., M.P.H.
M. Molly McMahon, M.D.
Mayo Clinic, Rochester, MN 559051
Owen WF Jr ,Lew NL ,Liu Y ,Lowrie EG ,Lazarus JM . The urea reduction ratio and serum albumin concentration as predictors of mortality in patients undergoing hemodialysis. N Engl J Med 1993;329:1001-1006
Full Text | Web of Science | Medline2
Perlmutter DH ,Dinarello CA ,Punsal PI ,Colten HR . Cachectin/tumor necrosis factor regulates hepatic acute-phase gene expression. J Clin Invest 1986;78:1349-1354
CrossRef | Web of Science | Medline
To the Editor:
Owen et al. confirm the not surprising notion that worse hemodialysis in patients with end-stage renal disease is associated with higher mortality. Thus, their work sets a floor, not a ceiling, for evaluating the efficacy of hemodialysis. They do not state directly the yearly gross mortality rate among their patients or in the United States, yet this rate remains close to 20 percent as reported by their group1. They imply that a reduction of 60 percent in the blood urea nitrogen concentration per dialysis treatment is sufficient. A much lower mortality rate of about 3 percent per year can be achieved with more vigorous dialysis,2 probably corresponding to a urea-reduction ratio of 80 percent or more per treatment. Thus, a 60 percent reduction in urea per treatment may not amount to really good dialysis.
In addition, serum albumin concentrations in patients undergoing hemodialysis are not an independent variable but are dependent on the efficacy of dialysis. Nutritional status is enhanced in patients with better dialysis3. Such patients have better appetites and eat more than those whose dialysis is less good. If we accept a urea-reduction ratio of 60 percent as the standard instead of striving toward truly better dialysis, we will take a step backward.
3 ReferencesEric P. Cohen, M.D.
Medical College of Wisconsin, Milwaukee, WI 532261
Lowrie EG ,Lew NL . Death risk in hemodialysis patients: the predictive value of commonly measured variables and an evaluation of death rate differences between facilities. Am J Kidney Dis 1990;15:458-482
Web of Science | Medline2
Charra B ,Calemard E ,Ruffet M , et al. Survival as an index of adequacy of dialysis. Kidney Int 1992;41:1286-1291
CrossRef | Web of Science | Medline3
Lindsay RM ,Spanner E ,Heidenheim P ,Kortas C ,Blake PG . PCR, Kt/V and membrane. Kidney Int Suppl 1993;41:S268-S273
Medline
Author/Editor Response
Dr. Owen replies:
To the Editor: We agree with Drs. Hensrud and McMahon that hypoalbuminemia in patients undergoing hemodialysis may be a manifestation of coexisting diseases other than malnutrition. However, some patients treated with hemodialysis have primary malnutrition,1 which probably contributes to hypoalbuminemia in this group. Several observations, as follows, support the hypothesis that hypoalbuminemia is caused by malnutrition: a low serum albumin concentration replaces diabetes mellitus as a risk factor for death in patients undergoing hemodialysis (not the other way around); intradialytic hyperalimentation increases the serum albumin concentration and may lower the risk of death; and other laboratory surrogates of nutritional status, such as serum creatinine or cholesterol concentrations, are predictors of mortality among patients undergoing hemodialysis2-4. These data support the importance of monitoring for malnutrition in these patients, rather than simply ascribing hypoalbuminemia to a coexisting event.
We agree with Dr. Cohen's interpretation that this work sets a minimal standard for solute clearance during hemodialysis. However, the lower limit as defined in our article exceeds the urea-reduction ratio of 50 percent that was suggested by the National Cooperative Dialysis Study, and the low values delivered to many patients receiving hemodialysis in the United States.
We do not agree that serum albumin concentrations depend on solute clearance within the range of urea-reduction ratios in this study. We found no correlation between the reduction in urea and the serum albumin concentration. Dr. Cohen's suggestion of improved nutrition for patients that parallels augmented solute clearance is based on pharmacokinetic equations that model the interdialytic urea-generation rate as a surrogate for dietary protein intake and on solute clearance during dialysis5. Because these values are calculated from the same parent data, they cannot be considered to be independent of each other and therefore should not be used together in a correlation analysis.
We think that improving the nutrition of patients undergoing hemodialysis requires more than simply increasing the dialysis prescription. We could not demonstrate an improved odds ratio for death with solute clearances that exceeded a urea-reduction ratio of 65 to 70 percent. The mortality rates among our patients and among all patients undergoing hemodialysis in the United States were as stated in the article.
5 ReferencesWilliam F. Owen, Jr., M.D.
Brigham and Women's Hospital, Boston, MA 02115for the Authors
1
Schoenfeld PY ,Henry RR ,Laird NM ,Roxe DM . Assessment of nutritional status of the National Cooperative Dialysis Study population. Kidney Int Suppl 1983;13:S80-S88
Medline2
Cano N ,Labastie-Coeyrehourq J ,Lacombe P , et al. Perdialytic parenteral nutrition with lipids and amino acids in malnourished hemodialysis patients. Am J Clin Nutr 1990;52:726-730
Web of Science | Medline3
Lowrie EG ,Lew NL . Death risk in hemodialysis patients: the predictive value of commonly measured variables and an evaluation of death rate differences between facilities. Am J Kidney Dis 1990;15:458-482
Web of Science | Medline4
Lowrie EG ,Lew NL ,Huang WH . Race and diabetes as death risk predictors in hemodialysis patients. Kidney Int Suppl 1992;38:S22-S31
Medline5
Lindsay RM ,Spanner E . A hypothesis: the protein catabolic rate is dependent upon the type and amount of treatment in dialyzed uremic patients. Am J Kidney Dis 1989;13:382-389
Web of Science | Medline
- Citing Articles (2)
Citing Articles
1
Akira Joraku, Kathryn A. Stern, Anthony Atala, James J. Yoo. (2009) In vitro generation of three-dimensional renal structures. Methods 47:2, 129-133
CrossRef2
Hiroko Ohwada, Takeo Nakayama. (2008) The distributions and correlates of serum albumin levels in institutionalised individuals with intellectual and/or motor disabilities. British Journal of Nutrition 100:06, 1291
CrossRef
