Many patients on chronic hemodialysis therapy exceed the recommended values of interdialytic weight gain (IDWG) of 4.0% to 4.5% of dry weight; some have IDWG of 10% to 20%. There are associations between higher IDWG and increased risk of all-cause and cardiovascular death. IDWG has also been shown to be a risk factor for increased morbidity, including ventricular hypertrophy and major adverse cardiac and cerebrovascular events. IDWG can also create the need for supplementary weekly dialysis sessions, with subsequent negative affect on quality of life and healthcare costs.
High IDWG is secondary to excessive intake of fluids and/or foods. An estimated 30% to 60% of patients on hemodialysis do not adhere to a fluid intake regimen. Thirst and xerostomia (the subjective feeling of a dry mouth) are the leading causes of poor adherence to fluid restriction.
Current clinical practice utilizes various strategies to limit IDWG. Maurizio Bossola, MD, and colleagues recently presented a review article evaluating the efficacy of the strategies used in routine clinical practice and tested in clinical trials. The review was published in the Journal of Renal Nutrition [2018;28(5):293-301].
Relevant studies up to October 2014 were identified using Medline, PubMed, Web of Science, and the Cochrane Library. The search terms used were hemodialysis OR dialysis AND weight gain OR interdialytic OR interdialytic weight gain OR thirst OR xerostomia OR dialysate OR sodium dialysate concentration. A total of 470 manuscripts were reviewed and 81 were included in the current review.
The basis for the strategy to limit IDWG is reduction of thirst and improvement of motivation and knowledge to increase adherence to fluid restriction. Interventions used to reduce thirst in patients on chronic hemodialysis are reduction of dietary salt intake, improvement of xerostomia, and the use of lower dialysate sodium concentration.
Guidelines from the National Kidney Foundation Kidney Disease Outcomes Quality Initiatives note that “Advising patients to limit their water intake without curtailing their salt intake will cause suffering from unnecessary thirst. Some of these patients may even feel guilty if they fail to resist the urge to drink in the face of marked thirst.”
Patients on chronic hemodialysis therapy should restrict salt intake to no more than 5.0 g/day (2 g of sodium). The estimated average daily salt intake among dialysis patients may range from 7.9 to 14.1 g/day. There are geographic variations in salt intake of hemodialysis patients; salt intake is higher in areas where the diet is rich in processed foods.
Factors that contribute to poor adherence to salt restriction include lack of knowledge, interference with socialization, and lack of food selections. Patients with poor adherence have lower education level and lower socioeconomic status compared with patients with improved adherence.
Overall, two strategies have been used to reduce salt intake: (1) prescription of a diet with low salt content; or (2) nutritional counseling. Results of a 1997 study indicated that nutritional counseling and social cognitive theory-based behavioral counseling did not reduce dietary salt intake or IDWG; in a randomized controlled study, 2 g of sodium restriction on patients’ habitual diet did not reduce IDWG. Two small 1999 studies did show that adherence to a low-salt diet was reliable and associated with reduced IDWG, and a 48-month program of nutritional counseling resulted in a significant decrease of salt and water intake as well as of IDWG. “Overall, it seems that efforts should be made to design adequate, randomized controlled studies to determine if salt restriction may reduce IDWG and define the entity of such restriction in terms of grams per day,” the review authors said.
Behavioral interventions designed to improve adherence to fluid restriction have been based on a variety of approaches, including behavioral contracting and weekly telephone contacts with patients, patient self-monitoring and behavioral contracting upon adherence. Stepped verbal and written reinforcement, group-administered behavioral self-regulation intervention, group education sessions based on transtheoretical model (states of change), self-efficacy training, and group or individual cognitive behavioral therapy. Results of trials testing those models have not produced clear conclusions regarding their efficacy.
At present, there is no valid therapy for xerostomia in patients receiving chronic hemodialysis therapy. There have been three studies designed to assess the effect of sugarless chewing gum on hemodialysis patients with xerostomia; however, the three studies had conflicting results.
In a randomized crossover study, the use of sugarless gum was compared with use of a saliva substitute for 6 weeks. There was significant reduction in xerostomia in patients in the sugarless gum group, and both treatments significantly reduced thirst; there were no differences in IDWG between the two groups. In contrast, a study conducted in a cohort of 38 chronic hemodialysis patients with regular use of sugarless gum for 3 months did not result in alleviation of xerostomia or reduction of IDWG. Results from another recent randomized controlled study demonstrated that chewing gum for 15 minutes each hour during a hemodialysis session was ineffective in increasing salivary flow and improving xerostomia.
A recent study among 28 patients on hemodialysis therapy found an association between acupressure at two acupoints (CV23 and TE17) for 4 weeks and a significant increase in salivary flow rate, thirst improvement, and reduction of the frequency of xerostomia; however, there was no evaluation of the long-term effects of the acupuncture treatment. In another study designed to test the efficacy of a salivary substitute in patients on chronic hemodialysis, the use of the agent for 2 weeks did not reduce xerostomia, thirst, and IDWG or increase salivary flow.
Finally, in eight studies evaluating the effect of the use of lower dialysate sodium concentration on IDWG, four demonstrated an association and four did not. In addition, the number of patients in the majority of the studies was low, and only one was prospective and randomized. Of note, a small recent longitudinal study has shown that the gradual reduction of sodium dialysate concentration from 140 to 135 mEq/L in 5 months significantly reduced IDWG by 0.39 kg.
In summary, the authors said, “It is still difficult to limit IDWG in patients on chronic hemodialysis. The therapeutic strategies used so far have shown to be of limited efficacy in terms of size and duration. The low-salt diet is effective, but unfortunately, it is characterized by poor adherence. Xerostomia represents an important target to reduce IDWG, but a valid therapy is still lacking. The use of individualized sodium dialysate seems a promising strategy. Behavioral interventions aimed at improving adherence to fluid restriction have led to encouraging—albeit short-term—results. Nevertheless, experimental and innovative treatments are lacking. It seems that research efforts should focus on a better understanding of the mechanisms of thirst and xerostomia as well as on an improvement of their management. Further clinical investigations should be made also in individualized sodium dialysate. The scientific and clinical communities should gain complete awareness of the problem and try to find an adequate and rapid remedy.”
Takeaway Points
- Researchers conducted a literature search to assess the efficacy of current strategies used to limit interdialytic weight gain (IDWG) in patients on chronic hemodialysis.
- A low- salt diet is effective; however, it is associated with poor adherence. Treatment of xerostomia offers a promising path to reduction of IDWG, but a valid therapy is yet to be developed.
- Gradual reduction of sodium dialysate concentration has been shown to be effective in reducing IDWG in this patient population in a recent small longitudinal study.
