Dogma and the Renal Patient
* Nephrologist in private practice, Dayton, Ohio,
and Correspondence: Pam Charney, MS, RD, LD, CNSD, 10772 Country Walk Court, Dayton, OH 45458. Electronic mail may be sent to charnepa{at}umdnj.edu Nutrition care of the patient with renal disease is relatively complex, given the significant number of potential metabolic derangements seen in this population. Many clinicians describe a high level of uncertainty regarding care for patients with either acute or chronic renal failure. Professionals attempting to care for these patients should be able to turn to the medical literature for guidance in making rational, appropriate decisions regarding this care. Unfortunately, the nephrology literature is rife with articles purporting to represent evidence-based recommendations, when in fact the conclusions made are the opinion of the author(s). The initial fault in the nephrology literature is a lack of controlled trials of significant size and design to allow for conclusions regarding patient care to be drawn. This deficiency was most apparent in the publication of the Kidney Disease Outcomes Quality Initiative (K/DOQI) by the National Kidney Foundation.1 This initiative represented an exhaustive review of the nephrology literature in a number of areas of care of the renal patient, including nutrition. However, the result of this review was both a dearth of evidence-based guidelines and the repeated request for more research to be performed. The K/DOQI guidelines for nutrition, for example, contained 22 of 27 guidelines that were, at least in part, opinion based. Given the lack of a literature basis for evidence-based nephrologic practice, authors of review articles will have a tendency to pursue 1 of 2 approaches. One approach results in the presentation of as complete a description of the disease process as possible, with a rational approach to evaluation or treatment offered as an option. The alternative is a presentation fostering a specific opinion as the only interpretation, regardless of the evidence or lack thereof. In this issue of Nutrition in Clinical Practice, we provide an overview of issues and controversies associated with provision of nutrition support to patients with acute and chronic renal failure. An expert panel of authors provides the reader with information pertinent to everyday care of these complex patients. There is still so much that we don't know about the impact of our nutrition interventions on outcomes in acute renal failure (ARF). We know that nutritional status is an important prognostic indicator in maintenance hemodialysis (MHD), but we still don't have the definitive standards to determine nutritional status. It's time to reevaluate the paradigms now entrenched in practice. Is albumin the definitive marker of nutritional status in MHD patients? Is intradialytic parenteral nutrition (IDPN) safer and more effective than enteral nutrition, or are we treating a clinician bias against enteral feeding? What is the optimum protein intake for ARF, and do we need to consider specific amino acids as being essential for these very sick patients? Finally, is carnitine deficiency widespread in this population, or can these patients synthesize adequate amounts?
Nutrition assessment is the critical first step in provision of nutrition care.2 Timely and appropriate determination of nutritional status and estimation of the risk for complications thought to be related to inadequate nutrient intake or metabolism are especially important when caring for patients with renal failure. Without an appropriate nutrition assessment, it is impossible to diagnose nutrition-related problems, develop interventions addressing those problems, and monitor the effectiveness of those interventions. Kamimura et al3 discuss some of the methods currently in use to assess the nutritional status of patients with end-stage renal disease who require MHD. They correctly identify some of the problems surrounding the use of hepatic transport proteins in assessing the nutritional status of these patients. Although albumin levels are associated with increased risk of mortality in this population, we postulate that the association in this population is caused by concurrent illness and physiologic stress more than nutrition. If we consider that the hemodialysis patient has a low-level acute-phase response, then albumin (and other hepatic transport proteins) will act in response to that stress rather than nutrition.4,5 This might identify those individuals who require nutrition intervention and monitoring because of level of illness, but it does not say much about concurrent nutritional status. Although the Dialysis Outcomes Quality Initiative (DOQI) recommends use of hepatic transport proteins and, more specifically, albumin levels for assessment of nutritional status, there is also the recommendation to combine use of the hepatic transport protein levels with other indicators of nutritional status.6 Using a combination of parameters allows for more global assessment of nutrient intake and the functional and metabolic results of that intake (or lack thereof). Other markers of nutritional status (such as dietary intake, anthropometric measurements, and other laboratory values) are discussed. Various indices and scoring systems to assess nutritional risk are thoroughly discussed and exhaustively referenced so that the clinician can use this information to determine the best methods to assess nutritional status in a particular population. Although we continue to struggle with the best methods to determine nutritional status in this population, the information in the article by Kamimura et al3 provides a good review for those caring for these patients.
In this issue of Nutrition in Clinical Practice, Schreiber7 provides a detailed background on carnitine and its metabolic functions. The author proposes the expanded use of L-carnitine supplementation in chronic-dialysis patients and cites the recommendations of the National Kidney Foundation Carnitine Consensus Conference that said, in part: "There are some differences between the recommendations of the panel and the clinical practice guidelines of NKF Kidney Disease Outcomes Quality Initiative (K/DOQI). The clinical practice guidelines follow established methods for the development of an evidence report on which each guideline is based. The panel recognized that current literature and clinical experience leave unanswered questions that do not allow the development of clinical practice guidelines for the use of L-carnitine in dialysis patients. As such, the recommendations made by the panel are not based on the same type of process as used in the development of the clinical practice guidelines and neither can they be as focused or detailed as guidelines. Rather, the panel anticipates that the recommendations made will provide direction to clinicians treating dialysis patients and will offer specific criteria to evaluate and document the outcomes of the intervention. —A systematic, prospective collection of data on the clinical use of L-carnitine and the resultant measurable patient outcomes, as recommended in this document, would substantially expand the understanding of the value of this therapy. To achieve that goal, the panel recommended that a national registry be created to collect prospective data on measurable patient outcomes in those who are treated with L-carnitine as a component of the implementation of these best practice recommendations."8 In the ongoing lack of such a national registry, this statement essentially becomes an invitation for clinicians to perform their own "n-of-1" trials with patients. It appears that Schreiber7 presents the recommendations of the conference as justification for use of L-carnitine therapy in the dialysis population. Contrast the quote above with the statement in the K/DOQI nutrition guidelines: "There was complete agreement that there is insufficient evidence to support the routine use of L-carnitine for maintenance dialysis patients."9 Schreiber nicely discusses potential uses of carnitine supplementation in MHD patients. There is a subset of MHD patients who most certainly will benefit from carnitine supplementation. At this point, routine use of this supplement cannot be recommended in the absence of evidence-supporting benefits.
Moore and Celano10 provide a review of the factors that contribute to malnutrition in MHD. This article includes a nice review of the use of nutrition counseling and diet supplementation that shows that intensive counseling and diet changes can improve nutritional status in this population. This intensive discussion seems to not support the use of IDPN as appropriate therapy for malnutrition in this population. Following documentation of a number of reasons why this therapy is inappropriate, the authors then conclude that IDPN is useful in such patients. This article fails to bring up the point that in no other patient population would the use of intermittent PN providing a fraction of requirements be recommended. The patient's or physician's personal preference for PN is not normally felt to be an appropriate indication for the switch from enteral to parenteral nutrition. A critical review of the literature on IDPN could conclude that IDPN is an expensive therapy whose main benefit is the ease and acceptance by the patient and nephrologists, without clear improvement in outcome over less-expensive therapies.11 Current funding levels limit the time that the average renal dietitian has with patients receiving MHD. It may be more cost-efficient to investigate further use of intensive counseling and education before resorting to other expensive therapies.
Also in this issue, Wooley et al12 and Nanovic13 provide balanced overviews of care for critically ill patients with ARF requiring renal replacement therapy (dialysis).12 These patients are some of the sickest and most challenging for which the nutrition support clinician will be caring. ARF carries with it a high mortality rate and leads to alterations in fluid and electrolyte status that make provision of nutrition support difficult in the best of situations. Nanovic's review13 of fluid and electrolyte management in renal replacement therapy should be required reading in every nutrition support training program.13 Wooley et al12 also provide a well-referenced review of the metabolic alterations seen in ARF. The use of continuous renal replacement therapy (CRRT) in the intensive care unit is becoming more common, and it is imperative that clinicians understand the nutritional ramifications of such therapy. The authors present a case that illustrates the complicated course that many of these patients experience. Although CRRT certainly allows much more liberalization of fluid and electrolyte provision, there is still the need for vigilant monitoring of this complex therapy.
There is a push by administrators, consumers, and third-party payers for more evidence-based guidelines for care in many patient populations. Development of such guidelines in nutrition care of the patient with renal failure is hampered by the lack of research specific to this population. Until we have more solid evidence supporting practices such as IDPN and carnitine supplementation, we cannot advocate for routine use. The articles in this issue of Nutrition in Clinical Practice provide a basis for discussion of these therapies and show that some patients may benefit from carefully monitored use. What we do know about nutrition in the patient with renal failure is that high degrees of provider knowledge and flexibility are needed to ensure that nutrition needs are met while taking into account the other factors that affect the care of both the patient receiving MHD and the critically ill patient with ARF. Patients requiring MHD frequently have other medical and socioeconomic issues that challenge providers to individualize all aspects of therapy to allow optimal functional status and quality of life. Patients with ARF are among the sickest patients and have a high mortality risk. The nutrition support clinician caring for either of these patient groups should be familiar with the concepts presented in this issue of Nutrition in Clinical Practice and the evidence-based process to evaluate information presented. Each of the authors herein has presented an exhaustive review of literature that could serve as a springboard for such review.
Nutrition in Clinical Practice, Vol. 20, No. 2,
159-161 (2005)
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