Correspondence

Effect of the Dialysis Membrane in Acute Renal Failure

N Engl J Med 1995; 332:961-962April 6, 1995

Article

To the Editor:

We found the study by Hakim et al. (Nov. 17 issue)1 comparing biocompatible and bioincompatible dialysis membranes for the treatment of acute renal failure interesting but flawed in several respects. The improvement in survival in the patients without oliguria can only be considered to be due to differences in the membrane used for dialysis if the original patients were evenly randomized according to their risk of death, a presumption that the authors attempted to support on the basis of the similarity of the raw Acute Physiology, Age, and Chronic Health Evaluation (APACHE II) scores. The APACHE II score, however, is only one factor in an exponential equation that must be used to determine the risk of death.2 Also included in this equation is a diagnostic-category weight. Thus, if the main diagnostic category was renal, patients with an APACHE II score of 29 would have an expected mortality rate of 46 percent, but if the diagnostic category was gastrointestinal, the expected mortality rate would be 77 percent.

This study also leaves many unanswered questions regarding the patients and their overall care. The indications for initiating or terminating dialysis are not clearly stated; the amount and type of nutrition and the amount of solute clearance, both factors known to affect the survival of patients with acute renal failure, are not described.3,4

This paper has raised the level of awareness of the variability of dialysis in patients with acute renal failure but has not convinced us that the choice of membrane alone has a major role in the outcome.

Andre A. Kaplan, M.D.
University of Connecticut Health Center, Farmington, CT 06030

Emil P. Paganini, M.D.
Cleveland Clinic Foundation, Cleveland, OH 44195

Juan P. Bosch, M.D.
George Washington University, Washington, DC 20037

4 References

1. 1

   Hakim RM, Wingard RL, Parker RA. Effect of the dialysis membrane in the treatment of patients with acute renal failure. N Engl J Med 1994;331:1338-1342
   Full Text | Web of Science | Medline

2. 2

   Knaus WA, Draper EA, Wagner DP, Zimmerman JE. APACHE II: a severity of disease classification system. Crit Care Med 1985;13:818-829
   CrossRef | Web of Science | Medline

3. 3

   Abel RM, Beck CH Jr, Abbott WM, Ryan JA Jr, Barnett GO, Fisher JE. Improved survival from acute renal failure after treatment with intravenous essential l-amino acids and glucose: results of a prospective, double-blind study. N Engl J Med 1973;288:695-699
   Full Text | Web of Science | Medline

4. 4

   Storck M, Hartl WH, Zimmerer E, Inthorn D. Comparison of pump-driven and spontaneous continuous haemofiltration in postoperative acute renal failure. Lancet 1991;337:452-455
   CrossRef | Web of Science | Medline

Author/Editor Response

The authors reply:

To the Editor: Dr. Kaplan and his colleagues raise several points regarding the comparison between the two treatment groups in our study. The first is that the APACHE II system for predicting mortality relies on the diagnostic-category weight. Including the diagnostic-category weights in the multiple logistic-regression model had little influence on the statistical significance of the effect of the type of membrane used for dialysis in either patients with oliguria or patients without oliguria with respect to survival or recovery of renal function. It might have been useful to calculate the expected mortality rates with the weighted APACHE II system if we had been comparing the actual mortality rate in our patients with predicted mortality.1 However, we were interested primarily in comparing the mortality in the two groups of patients.

The second point is the equality of the dialytic and nondialytic treatment of these patients. We did not control the overall care of these patients, and all management decisions were made by the attending physicians, except the decisions regarding the dialysis, including the initiation and termination of dialysis, which were made by the consulting nephrologists. Although the latter may have been aware of the type of membrane used, we have no evidence suggesting any bias in these decisions. The frequency of hypotension during dialysis, a major treatment variable that was measured in our study, was the same in both treatment groups. Both the time to recovery and the development of oliguria were affected by the type of membrane but were not likely to have been influenced by the number of dialysis treatments. Whether parenteral nutrition is beneficial in patients with acute renal failure is uncertain.2 We believe, therefore, that the treatment of the two groups was comparable. Nevertheless, the choice of dialysis membrane is not the only determinant of outcome in patients with acute renal failure.

Raymond M. Hakim, M.D., Ph.D.
Rebecca L. Wingard, R.N., M.S.N.
Robert A. Parker, D.Sc.
Vanderbilt University Medical Center, Nashville, TN 37232-2372

2 References

1. 1

   Maher ER, Robinson KN, Scoble JE, et al. Prognosis of critically-ill patients with acute renal failure: APACHE II score and other predictive factors. Q J Med 1989;72:857-866
   Web of Science | Medline

2. 2

   Clinical Efficacy Assessment Subcommittee of the Health and Public Policy Subcommittee, American College of Physicians. Role of parenteral nutrition in inflammatory bowel disease, acute renal failure, and hepatic encephalopathy. Int J Technol Assess Health Care 1990;6:655-662
   CrossRef | Medline

Citing Articles (4)

Citing Articles

1. 1

   Achim Jörres, Gerhard M Gahl, Clemens Dobis, Momir H Polenakovic, Koco Cakalaroski, Boleslaw Rutkowski, Ewa Kisielnicka, Detlef H Krieter, K Wolfgang Rumpf, Christian Guenther, Wilhelm Gaus, Josef Hoegel. (1999) Haemodialysis-membrane biocompatibility and mortality of patients with dialysis-dependent acute renal failure: a prospective randomised multicentre trial. The Lancet 354:9187, 1337-1341
   CrossRef

2. 2

   Francesco Locatelli, Francesco Mastrangelo, Bruno Redaelli, Claudio Ronco, Daniele Marcelli, Giuseppe La Greca, Giancarlo Orlandini. (1996) Effects of different membranes and dialysis technologies on patient treatment tolerance and nutritional parameters. Kidney International 50:4, 1293-1302
   CrossRef

3. 3

   Jonathan Himmelfarb. (1996) Dialytic Therapy in Acute Renal Failure: No Reason for Nihilism. Seminars in Dialysis 9:3, 230-234
   CrossRef

4. 4

   Manuel Pascual, Nina Tolkoff-Rubin, Jürg A Schifferli. (1996) Is adsorption an important characteristic of dialysis membranes?. Kidney International 49:2, 309-313
   CrossRef