Nutrition plays a critical role in the management of renal disease. The diet will vary considerably depending on the type and stage of renal disease as well as on patient and treatment modality–specific factors. Diet may slow the progression of kidney disease in any of the first four stages. A “renal diet” that can be applied to all patients does not exist. Each situation must be evaluated individually. Certain commonalities may apply to patients with chronic and acute renal disease; however, dietary requirements change with the progression of chronic kidney disease (CKD). Dietary restrictions are often considered the most difficult challenge the CKD patient may encounter. Fluid restrictions add an additional burden to the CKD patient on maintenance dialysis.
Why is diet important for people with renal disease?
Diet therapy offers the following potential benefits:
• It may be helpful in delaying the need for dialysis.
• Diet can help attenuate many of the complications of renal disease (e.g., phosphorus restriction to aid in prevention of bone disease).
• Adequate protein and calorie nutrition can influence morbidity and mortality in patients with renal disease.
• Quality of life for people with CKD may be improved by individualization of diet to suit lifestyle, ethnic, and socioeconomic variables.
What is the role of the registered dietitian?
The renal dietitian must be a registered dietitian with the Commission on Dietetic Registration and have a minimum of one year of professional work experience in clinical nutrition as a registered dietitian.
The registered dietitian is part of the facility’s interdisciplinary team and, as such, makes recommendations for the patient’s treatment plan. The dietitian will also work with the nephrologist and make a recommendation for the patient’s diet prescription. Patient and family are taught specifics of the diet by the dietitian, who monitors nutrition-related parameters and reevaluates needs. The dietitian is responsible for the primary diet education and functions as a member of the interdisciplinary team. Communication between the dietitian, nurses, technicians, physician, and social worker as to changes in a patient’s medical condition, dialysis treatment, medications, psychosocial situation, and nutritional status is critical to providing optimal patient care.
What nutritional parameters are assessed in the patient with chronic kidney disease?
The patient’s nutritional status must be monitored and evaluated by a qualified dietitian. The dietitian will monitor the patient’s nutritional status, hydration status, appetite, ability to chew and swallow, and use of dietary or herbal supplements. Glycemic control is important to monitor in the patient with diabetes. The dietitian will also assess a patient’s ability to prepare food and make recommendations to help the patient modify current dietary habits to better meet the requirements of the renal diet.
What diet concerns are there before initiation of dialysis?
Before dialysis, the diet is constructed to achieve several goals. One goal is to delay the need for dialysis by slowing the decline of renal function. At present, studies are inconclusive as to whether protein or phosphorus restriction can help slow the progression of renal disease. Kidney Disease Outcomes Quality Initiative (KDOQI) clinical practice guidelines for CKD suggest that patients with a glomerular filtration rate (GFR) less than 60 mL/min/1.73 m2should undergo assessment of dietary protein and energy intake and nutritional status.
In addition to possible delay in the progression of renal disease, protein restriction, when employed with an adequate caloric intake, can be helpful in minimizing nitrogenous wastes and can aid in the control of uremic symptoms. Diet management can often be effective in delaying the need for dialysis until the GFR falls below about 15 mL/min /1.73 m2, at which time some type of renal replacement therapy is necessary. Preservation of nutritional status by the provision of adequate calories to maintain or achieve a desirable body weight and avoid endogenous protein catabolism is of prime importance during this period.
Phosphorus control, through limiting high-phosphorus foods and/or the use of phosphate-binding medications, is often necessary when the GFR falls below 20 mL/min/1.73 m2. (Phosphorus control is discussed later in this chapter.)
Another diet concern before the initiation of dialysis is sodium control for the patient who is edematous or hypertensive. Potassium restriction is generally not necessary until urine output falls below 1000 mL/day; therefore, potassium restriction may not be necessary until after dialysis is initiated.
What are the diet modifications for hemodialysis?
The need for dietary modification after hemodialysis begins is highly individualized depending on such factors as height, weight, nutritional status, the level of residual renal function, laboratory data, intercurrent illnesses, and prescribed medications. Maintenance of good nutritional status, as evidenced by adequate anthropometric measurements and biochemical indices, is critically important during this period. Achieving and maintaining a normal serum albumin level is the primary goal of nutrition therapy for the hemodialysis patient. Various studies have demonstrated that the primary biochemical predictor of mortality in hemodialysis patients is a low serum albumin. In the absence of proteinuria or significant liver disease, albumin levels can be maintained with provision of adequate protein and calories. Although the diet is highly individualized, certain diet commonalities do apply to most patients on hemodialysis.
What amount of protein is appropriate for hemodialysis patients?
Protein requirements, as suggested by current research, are thought to be 1.2 ± 0.2 g/kg/day, with the upper end of the range considered appropriate for protein-malnourished patients. In general, at least 50% of this protein should be derived from high biologic–value protein sources, such as meat, fish, poultry, tofu, eggs, dairy, and cheese. Such protein sources contain a full complement of essential amino acids. Examples of low biologic–value protein are fruits, vegetables, legumes, and grains; however, a carefully planned vegetarian diet can be used without compromise of nutritional status (Fig. 14-1). The protein needs of hemodialysis patients are higher than those of the general population, in part because of the loss of 5 to 10 g of amino acid during each hemodialysis treatment.
Figure 14-1 Renal diet teaching aids: tips on protein intake.
(From Black JM, Hawks JH, Keene AM: Medical-surgical nursing: clinical management for positive outcomes, ed 7, Philadelphia, 2005, Saunders. Modified from Darlene Michl, Sidney, British Columbia.)
What caloric level is advisable?
Energy requirements for hemodialysis patients are not well defined, although they are generally accepted to be 35 kcal/kg/day for maintenance. With stress or malnutrition, caloric needs may be as high as 40 to 45 kcal/kg/day. For the obese patient, 25 to 30 kcal/kg/day may be appropriate.
What about potassium control?
Almost all foods contain potassium, and certain fruits and vegetables are particularly rich sources. When urine output falls below 1000 mL/day, and in some cases before this happens, potassium should be controlled in the diet. An intake of approximately 70 mEq or 2730 mg/day of potassium is safe for most hemodialysis patients. The specific dietary potassium intake depends on the size of the patient, the level of potassium in the dialysate, and other factors that may affect the serum potassium level. Factors other than dietary indiscretion may contribute to hyperkalemia, including severe acidosis, constipation, catabolism, insulin deficiency, and the use of certain medications, such as β-adrenergic–blocking agents and angiotensin-converting enzyme (ACE) inhibitors. The potassium content of selected foods may be found in Appendix C.
How much sodium is acceptable?
An intake of approximately 87 mEq or 2000 mg/day of sodium is appropriate for most hemodialysis patients. Adjustments can be made depending on blood pressure, urine output, and the presence or absence of edema. Hypertension in CKD patients is largely volume related, and dry weight should be constantly reassessed in the hypertensive patient. Renin-mediated hypertension is present in a small percentage of dialysis patients. Appropriate antihypertensive medications, rather than further sodium and fluid restriction, are necessary for this subgroup. The sodium content of specific foods may be found in Appendix C.
What level of fluid intake is acceptable?
Generally, the recommended fluid intake is 1000 mL/day or 1000 mL plus an amount equal to urine output. Fluids contained in foods, such as fruits and vegetables, are not usually counted in this total. Foods that are liquid at room temperature, such as Popsicles, soups, gelatin, and ice, are counted in the daily fluid allotment. The volume of fluid in solid foods, approximately 500 to 800 mL/day, is roughly equivalent to insensible fluid losses; therefore remaining “visible” fluid intake will correlate with interdialytic weight gain. An acceptable interdialytic weight gain is 1.5 kg, or less than 3% of body weight. Excessive fluid contributes to high blood pressure and results in left ventricular hypertrophy.
What about phosphorus and calcium intake?
Phosphorus intake should be limited to 800 to 1200 mg/day in those with CKD stage 5 (KDOQI Clinical Practice Guidelines for Bone Metabolism, 2003). Because phosphorus content of the diet correlates with protein intake, it may be necessary to include some high-phosphorus food to achieve an adequate protein intake. Phosphorus is also controlled by the intake of phosphate-binding antacids, such as calcium carbonate or calcium acetate. Aluminum-containing antacids should be avoided to minimize risk of aluminum bone disease. The calcium-containing antacids are given with meals and snacks, and ideally are titrated to the phosphorus content of the diet. Calcium content in the diet is typically low because foods high in phosphorus also tend to be rich sources of calcium. Calcium supplements, aside from the calcium in the phosphate-binding antacids, may not be necessary to maintain calcium balance when either oral or intravenous 1,25-dihydroxycholecalciferol is used. Calcium requirements vary considerably depending on the phosphate intake, the use of vitamin D, the calcium content of the dialysate, and the presence of hyperparathyroidism. This is discussed in greater detail in Chapter 17.
Are vitamin supplements necessary?
Patients on dialysis may be at risk for deficiencies of certain water-soluble vitamins because of poor nutrient intake, malabsorption, drug-nutrient interactions, altered vitamin metabolism, and dialysis losses. Although evaluation of specific requirements and recommendations is ongoing, supplementation with U.S. Recommended Daily Allowances (U.S. RDA) of vitamins B1, B2, and B12, biotin, pantothenic acid, and niacin, as well as 800 to 1000 mcg of folic acid and 10 mg of pyridoxine (B6) daily is reasonable. The recommendations for folic acid, B12, and B6 continue to be reevaluated in light of information concerning the amino acid intermediate, homocysteine. Elevated levels of homocysteine have been demonstrated to be a risk factor in cardiovascular disease and can be present in patients with CKD. High doses of folic acid, and in some studies B6 and B12, have been shown to normalize homocysteine levels and therefore may have a cardioprotective effect. The efficacy of high-dose supplementation of these B vitamins and the appropriate dosages are yet to be determined in the dialysis population. Vitamin C supplementation is limited to 60 mg/day. Higher doses of vitamin C should be avoided to prevent accumulation of oxalate, an ascorbic acid metabolite. Supplemental vitamin A should be avoided because of potential toxicity related to decreased renal degradation of retinol-binding protein in renal failure. Routine supplementation with a specially formulated vitamin is common in patients with CKD on maintenance dialysis.
What about the need for trace minerals?
Trace mineral requirements are not well defined for the dialysis patient, and at present routine supplementation is not appropriate. Zinc deficiency may be present in some patients on dialysis, although the best method of measuring stores is yet to be determined in this population. In a patient who exhibits signs of zinc deficiency—such as hypogeusia (loss of sense of taste), delayed wound healing, or alopecia—a time-limited trial of zinc supplementation may be reasonable. Selenium is another trace metal undergoing investigation into the possible role of selenium deficiency in promoting comorbid conditions, such as cardiovascular disease and cancer in the dialysis population. The optimal method of assessing selenium status and appropriate dosing remain to be defined.
How is iron deficiency assessed?
Iron deficiency is a common finding in dialysis patients receiving human recombinant erythropoietin and concomitant use of iron for erythropoiesis. Before the use of erythropoietin, iron overload was common in this population as a result of multiple blood transfusions (each unit of transfused blood contains approximately 200 to 250 mg iron). Routine assessment of iron stores by serum ferritin and percent transferrin saturation (iron divided by total iron-binding capacity) should be included in any erythropoietin therapy protocol.
A low mean corpuscular volume may be a late indicator of iron deficiency. If a deficiency is present, intravenous iron administration or oral iron supplementation is warranted. Increasing the iron content of the diet generally does not provide adequate replacement once iron deficiency is identified. Various oral forms of iron are available but may cause gastrointestinal upset. Guidelines for administering intravenous iron and erythropoietin therapy are described in Chapter 17.
Do people on dialysis have to control fat intake?
Dyslipidemia, typically seen as hypertriglyceridemia, combined with low high-density lipoprotein (HDL) cholesterol and normal total serum cholesterol, is the most common lipid abnormality found in dialysis patients. Some patients may present with elevated serum cholesterol, defined as serum cholesterol greater than 200 mg/dL. For these people, it may be appropriate to prescribe a low-cholesterol, low-fat diet.
Obesity may exacerbate hypertriglyceridemia. Therefore, in the obese dialysis patient, weight control may be of benefit in helping to control triglyceride levels. A regular aerobic exercise program may also be of benefit in helping control both cholesterol and triglyceride levels. Carnitine, discussed later in this chapter, and fish oil supplements also have been shown to help lower triglyceride levels.
What about sugar and carbohydrates?
Restriction of sugar and carbohydrates is not appropriate or necessary for most people on dialysis. Exceptions are diabetics or those who are overweight, or who have hypertriglyceridemia that may respond to total calorie restriction. Often sugars and other carbohydrates need to be increased to provide adequate calories in the diet.
How is nutritional status monitored?
Serum albumin and body weight are important to evaluate in the patient on maintenance dialysis at least monthly. One category of assessment tools is anthropometric measurements, which include height, weight, ideal or desirable body weight, weight changes, and other measurements, such as triceps skinfold (to assess fat stores) and midarm muscle circumference (to measure somatic protein stores). A second category is biochemical data. Serum albumin correlates with protein nutriture in stable hemodialysis patients in the absence of a nephrotic syndrome or liver disease, although levels are influenced by volume status. Data from the U.S. Renal Data System indicate that low serum albumin, as indicative of overall nutritional status, is associated with increased mortality in patients on hemodialysis. Serum albumin appears to be a less reliable indicator of nutritional status in patients on peritoneal dialysis (PD) and does not correlate well with mortality risk in these patients. Other biochemical parameters, such as serum transferrin, serum IGF-1 concentration, prealbumin levels, and low serum creatinine with low creatinine kinetics, have been used to assess nutritional status, although each parameter has limitations.
Subjective data, such as food diaries or diet recall obtained by a skilled interviewer, can provide valuable information. A method called subjective global assessment has been used to quantify nutritional status and includes physical assessment, functional impairment, gastrointestinal symptoms, as well as anthropometric indices. An assessment of the patient’s weight over the past six months, level of appetite, subcutaneous fat, and muscle mass are scored. The higher the score, the better the nutritional status and the lower the level of morbity and mortality. The goal is to recognize and treat malnutrition before it becomes severe and debilitating, making it difficult to treat.
What is urea kinetic modeling?
Urea kinetic modeling (UKM) is used to prescribe and monitor dialysis therapy and to assess protein intake. Although optimal methods for performing UKM and determining results are not agreed on in the dialysis community, formal UKM has become a standard of practice for both hemodialysis and PD programs. UKM is usually performed using a computer because the mathematical computations are elaborate. Blood urea nitrogen (BUN) levels from before and after a given dialysis treatment (some methods also include predialysis BUN from the subsequent dialysis treatment) are entered into the computer, and for patients who urinate, residual urea clearance is included. Information about the dialysis treatment (blood flow, dialysate flow, dialyzer clearance data, length of treatment, and interdialytic interval) and patient-specific data (predialysis and postdialysis weights, height, sex, and hematocrit) are also incorporated in the calculations.
What do the results of urea kinetic modeling mean?
One result derived from UKM is the Kt/V, which refers to the following:
K=Clearance of dialyzer for a given dialysis treatment and, if applicable, a measurement of any residual urine urea clearance
t=Length of time for a given dialysis treatment
V=Volume of distribution of urea for a given patient that equates with total body water
The goal for delivered Kt/V is thought to be, at minimum, 1.2 for thrice-weekly dialysis for both adults and children. Goal Kt/V for twice-weekly dialysis is undefined. Levels less than 1.2 may indicate inadequate dialysis and are associated with increased morbidity and poor prognosis on dialysis. Whether Kt/V can be too high and whether higher levels of Kt/V improve morbidity and mortality remains to be evaluated.
What other methods are available for estimating adequacy of dialysis?
Percent urea reduction or urea reduction ratio (URR) is another method used to assess dialysis adequacy. A 65% reduction of BUN during a given dialysis treatment roughly correlates with a Kt/V of 1.2 for patients on dialysis three times a week. URR is not a substitute for formal UKM because it does not reflect the contribution of residual renal function, does not reflect protein catabolic rate (PCR), and does not provide a means of evaluating the validity of results.
How is the urea reduction ratio calculated?
What is the protein catabolic rate?
PCR refers to a given patient’s protein intake expressed in grams of protein per kilogram normalized body weight, assuming that the patient is stable (that is, neither anabolic nor catabolic). The goal PCR is between 0.8 and 1.4 g protein per kilogram and is probably optimal at the upper end of the range.
What is the basis for interpreting the results of urea kinetic modeling?
Interpretation was based originally on the National Cooperative Dialysis Study (NCDS) published in 1983, in which an attempt was made to correlate patient outcome with amount of dialysis delivered. Both hospitalization and morbidity increased with high BUN levels in the presence of inadequate protein intake. The NCDS data later underwent a mechanistic analysis by Gotch and Sargent, from which the concept of Kt/V was derived. Since that time the generally accepted goals for Kt/V have continued to be reevaluated and revised upward.
What about urea kinetic modeling for peritoneal dialysis?
Studies comparable to the NCDS are not available in the PD population. Guidelines are available for determining urea clearance and weekly creatinine clearance as well as PCR for this treatment modality. For continuous ambulatory peritoneal dialysis (CAPD), the delivered dose of PD should be a Kt/V of at least 1.7 per week and a total creatinine clearance of at least 60 L/wk/1.73 m2 (NKF KDOQI Clinical Practice Guidelines for Peritoneal Dialysis Adequacy, 2006). Variables that can be manipulated to achieve targeted clearance include exchange volume, cycle time, ultrafiltration volume, continuous vs. intermittent therapy, and dwell time/drainage time.
Peritoneal equilibration testing (PET) is performed to assess the clearance capabilities of a given patient’s peritoneal membrane and to determine the optimal PD regimen. See Chapter 19 for further information on PET.
What can be done for the patient who is unable to eat?
The first step in helping a patient who is unable to eat is to determine why he or she cannot eat and how to correct it. This often can be best addressed by a team approach including nurse, dietitian, technician, physician, and social worker. Among the possible causes are underdialysis or uremia; gastroparesis; depression; intercurrent illness; poor dentition; constipation; side effects of medications; socioeconomic factors that influence the ability to obtain, prepare, or store foods; alcohol or drug abuse; and fatigue. These are but a few causes of poor nutritional intake. Inadequate intake and poor nutritional status should not be accepted as “normal” for dialysis patients. Each problem should be assessed and investigated because there is often an etiology that can be remedied.
When the identifiable causes of poor nutritional intake have been alleviated, certain strategies can be employed to augment nutrient intake. Commercially available supplements or homemade equivalents may be appropriate for some patients. The dietitian can evaluate the need for such supplements and recommend an appropriate type. Eating five or six small meals per day instead of two or three large ones may improve intake for some patients. The social worker can be helpful in enrolling a patient in a program, such as Meals on Wheels, or in involving the family in promoting food intake. Angel Food Ministries is a nonprofit, nondenominational organization that provides restaurant-grade food, such as meats, frozen vegetables, fruits, and dairy products, at a significant discount. There are no minimum income requirements or qualifications to participate and the organization currently distributes across 44 states. Food orders are placed with a local Angel Food host and then picked up at the host’s site.
Specific cultural habits and preferences are also incorporated when formulating a nutrition care plan. Medications to augment appetite have been used safely and effectively in patients with cancer and acquired immune deficiency syndrome (AIDS). These medications have not been well studied in the dialysis population but may be used when other strategies to augment oral intake have failed. Enteral nutrition via nasogastric, percutaneous endoscopic gastrostomy, or jejunostomy tubes should also be considered as an alternative method of providing support to the patient who is unable to eat but who has a viable gastrointestinal tract. If, despite these efforts, a patient continues to deteriorate nutritionally, intradialytic parenteral nutrition may be appropriate.
What are oral nutritional supplements?
CKD patients who are not meeting their nutritional needs may be offered oral nutritional supplements (ONS). These supplements may help to improve the serum albumin and nutritional status of the patient as well as reverse weight loss and decrease the morbidity and mortality associated with low serum albumins and malnutrition. Specially formulated ONS for the CKD patient are available with reduced potassium and phosphorus and high caloric and protein content. ONS usually come in the form of a liquid, powder, or bar. Examples of ONS include Nepro, ZonePerfect protein bars, Pro-Stat, and VitalProteinRx Protein Bars. Nutritional supplements are ordered by the physician and the dietitian can help to make recommendations on the best product for each patient.
What is intradialytic parenteral nutrition?
Intradialytic parenteral nutrition (IDPN) is a form of nutrition support by which protein, fat, and carbohydrate can be given during the dialysis treatment. Typically, a 1 L solution of amino acids, lipid solution, and dextrose is infused during a dialysis run through the venous drip chamber. This provides 800 to 1000 calories and 60 to 90 g of amino acids. The advantage is that nutrients can be provided with a concomitant removal of volume, and a central line is not necessary because the dialysis access serves as the line of administration. Although this method cannot meet a patient’s entire nutritional needs, it can provide supplemental nutrition for patients who are unable to take adequate intake by mouth, for whom enteral feeding is not an option, and for whom a central line is contraindicated. Approximately 90% of the amino acids infused are retained during this process. Potential side effects include hyperglycemia and reactive hypoglycemia.
Is there a comparable method of administering nutritional support for patients on peritoneal dialysis?
Intraperitoneal nutrition (IPN) is used in patients on PD, in which amino acids are substituted for a portion of dextrose in PD solutions. Maintaining good nutrition is sometimes a challenge in the PD patient due to large protein losses in the dialysate outflow. IPN is typically given during one or two exchanges in a 24-hour period and serves as both an osmotic agent and a protein source. It has been shown to improve protein nutritional status in patients on this modality; however, increased BUN concentrations and metabolic acidosis have been described as potential side effects. Cost factors may prohibit its widespread use.
What is protein energy wasting?
Protein energy wasting (PEW) refers to the presence of abnormalities in the protein-energy nutritional status of the dialysis patient leading to decreased body stores of protein as well as energy fuels. Low serum albumin levels, reduced body mass, and reduced muscle mass are the three characteristics present when identifying PEW. PEW is influenced by a number of factors identified in Box 14-1. PEW contributes to increased mortality in the CKD patient.
Box 14-1 Readily Usable Criteria for the Clinical Diagnosis of PEW in AKI or CKD
Serum chemistry
Serum albumin < 3.8 g/100 mL (Bromocresol Green)a
Serum prealbumin (transthyretin) < 30 mg/100 mL (for maintenance dialysis patients only; levels may vary according to GFR level for patients with CKD stages 2 to 5)a
Serum cholesterol < 100 mg/100 mLa
Body mass
BMI < 23b
Unintentional weight loss over time: 5% over 3 months or 10% over 6 months
Total body fat percentage < 10%
Muscle mass
Muscle wasting: reduced muscle mass of 5% over 3 months or 10% over 6 months
Reduced midarm muscle circumference areac (reduction > 10% in relation to 50th percentile of reference population)
Creatinine appearanced
Dietary intake
Unintentional low DPI < 0.80 g kg-1/ day-1 for at least 2 monthse for dialysis patients or < 0.6 kg-1/ day-1 for patients with CKD stages 2 to 5
Unintentional low DEI < 25 kcal kg-1/ day-1 for at least 2 monthse
AKI, Acute kidney injury; BMI, body mass index; CKD, chronic kidney disease; DEI, dietary energy intake; DPI, dietary protein intake; GFR, glomerular filtration rate; nPCR, normalized protein catabolic rate; nPNA, normalized protein nitrogen appearance; PEW, protein energy wasting.
Note: At least three of the four listed categories (and at least one test in each of the selected categories) must be satisfied for the diagnosis of kidney disease–related PEW. Optimally, each criterion should be documented on at least three occasions, preferably 2 to 4 weeks apart.
aNot valid if low concentrations are due to abnormally great urinary or gastrointestinal protein losses, liver disease, or cholesterol-lowering medicines.
bA lower BMI might be desirable for certain Asian populations; weight must be edema-free mass, for example, postdialysis dry weight. See Appendix D for the discussion of the BMI of the healthy population.
cMeasurement must be performed by a trained anthropometrist.
dCreatinine appearance is influenced by both muscle mass and meat intake.
eCan be assessed by dietary diaries and interviews or, for protein intake, by calculation of normalized protein equivalent of total nitrogen appearance (nPNA or nPCR) as determined by urea kinetic measurements.
Fouque et al: A proposed nomenclature and diagnostic criteria for protein-energy wasting in acute and chronic kidney disease, Kidney International 73(4):391–398, 2008.
What can be done for constipation?
Constipation is a common problem for people on dialysis and is often related to medication taken for phosphate binding. The usual recommendations for this problem given to people not on dialysis, such as increasing fluid intake, consuming relatively large amounts of bran products, and eating such foods as prunes and other fruits and vegetables, may not be appropriate for dialysis patients. Medications such as stool softeners or substances such as sorbitol, which draws fluid into the intestinal tract, may be necessary to alleviate constipation. In chronic renal failure, stool output is a major route of potassium excretion, allowing for 30 to 40 mEq/day of potassium excretion. In a patient with hyperkalemia that cannot easily be accounted for by increased potassium intake, constipation should be considered as a possible etiologic factor.
How does the diet differ for patients on peritoneal dialysis?
The diet for patients on CAPD, continuous cycling peritoneal dialysis (CCPD), and other PD modalities differs from that of patients on hemodialysis in several ways.
Protein. Protein needs are higher for patients on PD as a result of dialysate protein losses that average about 9 g/day. Levels of 1.2 to 1.3 g of protein per kilogram of body weight are prescribed and are often difficult to achieve, although there is evidence that some patients maintain positive nitrogen balance on lower protein intakes. As with hemodialysis, the general recommendation is that at least 50% of the protein should be derived from high biologic–value sources; however, it is possible to maintain good protein nutriture with a carefully planned vegetarian diet. Protein supplements may be used when needs cannot be met by high-protein foods alone.
Calories. Although caloric needs are the same for both hemodialysis and PD patients, those on PD absorb 150 to 1000 calories per day from the dextrose in the dialysate. This may provide a particular advantage in the patient who has energy malnutrition or may be problematic in the obese or hypertriglyceridemic patient.
Sodium/fluid. Typically, dietary sodium and fluid can be liberalized for the PD patient as compared with the same patient on hemodialysis because the dextrose content of the dialysis solution can be adjusted with each exchange to remove varying volumes of fluid. A sodium intake of 4 g, and a fluid intake as guided by thirst, can often provide acceptable fluid management, provided that dialysis can be adjusted to maintain euvolemia.
Potassium. Potassium control tends to be less of a problem in patients on PD in part because the constant glucose infusion combined with endogenous insulin production drives potassium intracellularly. Supplemental potassium may be indicated in approximately 10% of PD patients. Hyperkalemia may be present in others.
Phosphorus. Control of serum phosphorus presents a challenge for patients on PD. An obligatory higher phosphorus intake is often necessary to achieve an adequate dietary protein intake, because foods that are high in protein tend to be high in phosphorus. Requirements for phosphate binding medications may therefore be higher.
Vitamins and other minerals. The need for these other nutrients is generally thought to be the same as for patients on hemodialysis.
What is the diet for acute kidney injury?
There is no set diet for acute kidney injury because nutritional requirements vary considerably depending on comorbid conditions, degree of renal compromise, and presence of anuria or oliguria.
High mortality rates continue to be associated with acute renal failure, and protein-calorie malnutrition is thought to be one predictor of outcome. Although aggressive nutritional support has yet to be demonstrated to improve outcome, protein and calorie intake should be provided to meet increased needs associated with hypercatabolism. Protein requirements may be 1.5 g protein per kilogram per day or higher and can be determined using nitrogen balance studies. Both essential and nonessential amino acids should be used in most situations requiring parenteral nutrition. Caloric requirements vary considerably and can be best determined in the intensive care unit setting using indirect calorimetry.
Do the various treatment modalities influence the provision of parenteral nutrition?
Yes. The use of continuous arteriovenous or venovenous hemofiltration with or without dialysis allows for provision of large volumes of fluid necessary to give adequate amounts of parenteral nutrition in the hypercatabolic acute kidney injury patient. Renal replacement therapy, however, also contributes to the catabolic state because loss of nutrients (amino acids) and high-flux membranes increase these losses, in comparison with low-flux membranes. In addition, membrane characteristics, in particular bioincompatability, may further enhance catabolism.
What is carnitine and should it be routinely supplemented in patients on dialysis?
Carnitine is synthesized in the body from the essential amino acids lysine and methionine and plays a role in transporting long-chain fatty acids into the mitrochondria. Although methods of measuring carnitine in various metabolic pools in the body are imprecise, free plasma carnitine and muscle carnitine concentrations may be low in patients on dialysis. Carnitine has been used to lower triglyceride levels, help with muscle cramps and muscle weakness, and decrease red blood cell fragility in patients on dialysis. The questions of optimal dose and whether supplementation should be routine remain to be addressed.
Can the patient with chronic kidney disease use herbal remedies?
In recent years people have become increasingly aware of alternative therapies in medicine and diet. Supplementing diets with herbals, vitamins and minerals, and other supplements may provide some health benefits; however, these products must be used with caution in the CKD patient. Declining renal function causes changes in the pharmacokinetics of many medications, which leads to altered absorption, distribution, metabolism, and excretion. These changes necessitate dosage adjustments to prevent the patient from being exposed to toxic levels of certain medications. Without reliable information about the pharmacokinetic behavior of herbal remedies, supplements, and their potentially active or toxic metabolites in renal failure, their safe use remains almost impossible in this population (Dahl, 2001). Some believe these remedies are safe because they are labeled as “natural” and not viewed as drugs. Unfortunately, some of these remedies and natural products can have a deleterious effect on the kidneys and other organs of the body. Acute renal failure secondary to interstitial nephritis is associated with the use of certain Chinese herbal drugs, Aristolochia, in particular. Juice from the noni plant (Morinda citrifolia), which is promoted to increase mental clarity and improve physical performance, contains excessive potassium and should not be ingested by the CKD patient. The ingestion of star fruit has been associated with harmful outcomes in the CKD patient, causing neurologic symptoms, seizures, and intractable hiccups.
In the U.S., herbal remedies are not regulated by the U.S. Food and Drug Administration. Therefore the consumer must trust that the manufacturer has prepared and advertised its product in good faith. Some herbal remedies have a direct toxic effect on the kidneys and some may affect electrolyte balance, blood pressure control, and anticoagulation. Some products may interfere with efficacy of antirejection medications used in transplant patients. It is critical to question patients regarding their use of herbal supplements and alternative therapies because they are sometimes reluctant to reveal this information. Assessing for herbal remedy use should become part of the nursing assessment done on the CKD patient. Healthcare workers should become familiar with herbal remedies and their effects on the kidneys and the CKD patient. CKD patients should be encouraged to discuss the use of any herbal remedy with their nephrologist before use. Table 14-1 provides information on herbal remedies, their benefits, and their adverse effects.
Table 14-1 Herbal Remedies: Benefits and Adverse Effects
|
Herb |
Health benefit |
Adverse effects |
|
Aloe |
Used as laxative |
May cause cramps and diarrhea. Electrolyte imbalances, particularly hypokalemia, may occur over time. May interfere with absorption of some medications. |
|
Aristolochic acid |
Weight loss |
May cause permanent kidney damage or urinary tract malignancies. |
|
Echinacea |
Treats upper respiratory infections and flu |
Should not be used by patients with a transplant or those with AIDS. Allergic reactions are possible. |
|
Ephedra |
Used as decongestant |
Not recommended for dialysis or transplant patients. Should not be used by patients with heart disease, hypertension, thyroid disease, or diabetes. May increase blood pressure and heart rate. Other effects include heart palpitations and increased risk of stroke. Should not be used when taking antihypertensives or antidepressants. |
|
Garlic |
Improves blood lipid levels |
Should not be taken if using antihypertensives or anticoagulants. May increase bleeding tendencies. May decrease clotting times and cause heartburn. |
|
Ginkgo biloba |
Antioxidant |
Should not be used if taking anticoagulants. May cause headache, gastrointestinal problems, and dizziness. |
|
Ginseng |
Used as a stimulant or relaxant |
Should not be taken by those who have a transplant. May cause headaches, insomnia, anxiety, skin rash, and morning diarrhea. |
|
Hawthorn |
Used for heart disease |
May interfere with blood pressure and heart medications. |
|
Licorice root |
Used for the treatment of peptic ulcers and respiratory infections, cough suppressant, expectorant |
Should not be taken by those with kidney disease or glaucoma, or by those on antihypertensives, digitalis, corticoids, or diuretics. May cause sodium and water retention and significant potassium losses. |
|
St. John’s wort |
Used to treat moderate depression |
Not recommended for patients with renal failure. May cause headache, flulike symptoms, cough, fatigue, dry mouth, confusion, increased sensitivity to light, and gastrointestinal irritation. Should not be taken with antidepressants. May lower cyclosporine levels. |
Data from Bickford A: Therapies for kidney patients, Tampa, 2000, American Association of Kidney Patients; Allen D, Bell J: Herbal medicine and the transplant patient, Nephrol Nurs J 29(3):269–274, 2002; Myhre M: Herbal remedies, nephropathies, and renal disease, Nephrol Nurs J 27(5):473–478, 2000.
What about the needs of pediatric patients?
The basic concepts of diet management apply to pediatric patients with chronic renal failure, with one key exception: meeting the needs of protein, calories, and other nutrients to facilitate growth and development. The National Kidney Foundation released an update to the Clinical Practice Guidelines for Nutrition in Children with CKD in 2008. The goals are focused on maintaining an optimal nutritional status with near normal growth patterns, avoiding uremia toxicity and metabolic abnormalities, and reducing chronic illness and mortality in adulthood. Additional focus has been placed on the presence of overnutrition in this population and the dietary and lifestyle practices that play a contributing role.
Summary
In summary, dialysis therapy for the patient with either acute or chronic kidney disease can provide optimal patient outcomes when combined with effective and appropriate nutrition management. Although diet management is ultimately the responsibility of the patient or caretaker, members of the interdisciplinary team play a vital role in educating and reinforcing diet information that is tailored to the individual and monitored for effectiveness.