Fluid Management in Patients on Hemodialysis

Rory Caswell Pace

The human body is approximately 70% water. Healthy kidneys modify fluid excretion by excreting or reabsorbing water in the collecting tubules to maintain blood osmolality. This process is modulated by antidiuretic hormone (ADH), which is stimulated in response to increased osmolality and inhibited under conditions of hemodilution. Sodium, the major extracellular cation, influences extracellular fluid volume (Kopple & Massry, 2004). In individuals with chronic kidney disease (CKD) stage 5 on dialysis, the ability to concentrate or dilute urine is impaired, putting them at risk for volume expansion or contraction. Most commonly, people on dialysis struggle with fluid overload rather than depletion.

In the hemodialysis population, interdialytic fluid weight gain (IDWG) is a day to day challenge for patients and staff alike. Limiting fluid intake is one of a number of dietary restrictions that people on hemodialysis are faced with, and achievement of euvolemia through ultrafiltration can be a difficult task for dialysis providers. Excessive IDWGs may contribute significantly to morbidity and mortality for people on hemodialysis. Fluid overload is associated with a variety of co-morbidities (see Table 1). Additionally, the sequelae of fluid imbalance may negatively impact patients’ quality of life.

Data from the U.S. Renal Data System (USRDS) Waves 3 and 4 showed an increase in mortality with intradialytic weight gains of greater that 4.8% of body weight (Foley, Herzog, & Collins, 2002). The standard of care for patients in the author’s organization (Satellite Healthcare) is to limit fluid weight gains to 4% or less of estimated dry weight.

There are various approaches to prescribing fluid allowances for patients on hemodialysis. Kopple and Massry (2004) suggest recommended fluid intake be determined as:

Fluid allowance (mL/day) =
600 mL + urine output + extrarenal water losses where 600 mL represents the net daily water loss (900 mL/d insensible losses minus 300 mL water produced by metabolic processes).

Extrarenal water losses include diarrhea, vomitus, and nasogastric secretions. A simplified variation is proposed by Stover (1994), adding urine volume to 1000 mL as a baseline for insensible losses.

Others assert that dietary sodium restriction should be the primary focus in fluid management. Patients receiving hemodialysis are typically normonatremic, suggesting that the endogenous thirst mechanism regulates fluid intake to maintain blood osmolality, even when kidney function is significantly reduced (Rupp, Stone, & Gunning, 1978; Tomson, 2001). The KDOQI clinical practice guidelines advocate limiting dietary sodium intake to 2 g per day (National Kidney Foundation, 2006). Bots et al. (2005) have studied the relationship between xerostomia (dry mouth, which results from reduced or absent saliva production), thirst, fluid intake, and fluid weight gains. They demonstrated that the use of chewing gum reduced xerostomia and thirst, though it did not significantly impact IDWG.

Educating patients to manage fluids presents a challenge for the patient care team. Patients may ask about water in foods. However, as shown in Table 2, the moisture content of foods is variable and sometimes counterintuitive. It is therefore of limited benefit to track water from foods eaten and more common practice to focus on the volumes of liquids consumed. Patients are instructed to count all foods that are liquid at room temperature as part of their fluid intake, including ice cream, gelatin, soup, ice, popsicles, gravy, and yogurt.

Education Project

In an attempt to improve IDWGs at South County Dialysis, we undertook an education project involving both patients and staff. The goals of the project were to 1) educate patients about their individual fluid intake goals; 2) clarify the relationship between volume of fluid intake and fluid weight gain; and 3) raise awareness of volumes of fluids commonly consumed.

The project consisted of two components-clinic-wide visual displays and individually targeted packages for patients. Staff and patients were asked to collect cups from restaurants they visited. A variety of restaurants and cup sizes were represented. The volume of each cup was measured and recorded. Cups were paired with large droplet-shaped pages printed with their volume and equivalent weight in pounds and kilograms (see Figure 1). Cups and droplets were placed around the dialysis treatment area next to the televisions to create a visual display with maximum visibility. A variety of sizes/volumes were included, and they were presented in Spanish and English.
 
Goodie bags were prepared for each patient. They contained an 8-oz plastic measuring cup, an 8-ounce bottle of water, samples of Biotene® dry mouth products (Laclede, Inc, Dominguez, CA, USA), and a personalized reminder magnet. Printed in English or Spanish, the magnets included patients’ individual fluid intake goals in cups and ounces (see Figure 2). The magnets were created using Microsoft Word with clip art and were printed on 81/2” x 11” magnet sheets, available from office supply stores.

This informal patient education project did not include an outcomes measurement component. Observationally, however, some important outcomes were seen. First, the project successfully created teamwork between members of the dialysis team. Patient care technicians and registered nurses remarked that they had learned more about fluid volumes of common containers and were surprised by how much their estimates differed from the actual volumes. This generated discussion between staff and patients.

With the help of the magnets and education materials, more patients were able to state their fluid intake goals, and a few made significant improvements in their IDWGs. By providing measuring cups to every patient, we had the ability to encourage patients to actually measure the volume of their cups and containers at home rather than estimating. Because the focus of this project was to increase awareness of fluid volumes and IDWG, sodium restriction was not included. However, the importance of dietary sodium restriction should not be disregarded and is a logical topic for a future education project.

References
Bots, C.P., Brand, H.S., Veerman, E.C.I., Korevaar, J.C., Valentijn-Benz, M., Bezemer, P.D., duced or absent saliva production)et al. (2005). Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrology Dialysis Transplantation, 20, 578-584.

Foley, R.N,, Herzog, C.A., & Collins, A.J. (2002). Blood pressure and long-term mortality in United States hemodialysis patients: USRDS Waves 3 and 4 Study. Kidney International, 62, 1784-1790.

Kopple, J.D., & Massry, S.G. (2004). Nutritional management of renal disease (2nd ed.). Philadelphia: Lippincott Williams & Wilkins.

National Kidney Foundation. (2006). K/DOQI clinical practice guidelines for hemodialysis adequacy. Retrieved April 26, 2007, from http://www.kidney.org/professionals/kdoqi/guideline_upHD_PD_VA/index.htm

Rupp, J.W., Stone, R.A., & Gunning, B.E. (1978). Sodium versus sodium-fluid restriction in hemodialysis: Control of weight gains and blood pressures. The American Journal of Clinical Nutrition, 31, 1952-1955.

Stover, J.A. (1994). Clinical guide to nutrition care in end stage renal disease (2nd ed). Chicago: The American Dietetic Association.

Tomson, C.R. (2001).  Advising dialysis patients to restrict fluid intake without restricting sodium intake is not based on evidence and is a waste of time. Nephrology Dialysis Transplantation 16, 1538-1542.

U.S. Department of Agriculture. (2006). National nutrient database for standard reference. Retrieved April 26, 2007, from www.nal.usda.gov/fnic/foodcomp/search/