Clinical trial for the control of water intake of patients undergoing hemodialysis treatment*

ABSTRACT Objective: to analyze the impact of an educational and motivational intervention for patients with a chronic kidney disease, undergoing hemodialysis treatment, on the control of fluid intake during interdialytic periods. Method: a quasi-experimental, non-randomized clinical trial with patients from a Nephrological Unit of the State of São Paulo. Participants were included in two groups: Control Group with 106 patients and Intervention Group with 86 patients, totaling 192 participants. The used intervention was an educational and motivational video to control liquid intake, based on the Bandura’s Theory. The measure of control of water intake was the percentage of lost weight, also considered the variable outcome of the research. For the data analysis, descriptive analyses and regression analysis of the Inflated Beta Model were used. Results: patients who participated in the intervention had a decrease in the pattern of weight gain in interdialytic periods, with a 3.54 times more chance of reaching the goal of 100% of weight loss when compared to participants from the control group. Conclusion: the educational and motivational intervention was effective in reducing the percentage of weight loss in patients undergoing hemodialysis. Brazilian Clinical Trials Registry (ReBEC) under the opinion RBR-4XYTP6.


Introduction
Many of the problems experienced by patients with Chronic Kidney Disease (CKD) undergoing hemodialysis treatment are related to a low adherence to the proposed treatment. Fluid overload is common for these patients, and their excess is linked to an increase in the morbidity of this population (1)(2) .
Although it is regulated by physiological mechanisms, the behavior of fluid intake is also influenced by the person's habits, customs, and social rituals, as well as other factors that trigger water intake, such as a deficit in extracellular volume and blood pressure, and lack of moisture of the oral mucosa and esophagus (3) . Thirst plays a role in the maintenance of fluid homeostasis, which implies a network of complex neural and hormonal processes in response to an imbalance in the body's water and sodium ratio (4)(5) .
Many patients with CKD undergoing hemodialysis treatment intake more fluids than recommended, a practice that is common among these persons (6) . The management of liquid intake is a challenge for most patients since, in addition to the liquids, many foods have a high water content, such as fruits, jellies, and soups (7)(8)(9) . Approximately 95% of the patients with CKD undergoing hemodialysis do not adhere to the prescribed treatment for water restriction, which can lead to many complications (10) .
Patient education is one of the most useful, effective, and accessible health care tools (11) . Health behavior change is described as the result of reciprocal relationships between the environment, personal factors, and the attributes of one's behavior (12) .
The theory underlying the elaboration of educational material and its implementation in this study was the Cognitive-Social Theory, whose basic principle is the perspective of human agency for self-development, adaptation, and change. Human thought and action are considered as products of a dynamic interrelationship between personal, behavioral, and environmental influences, which enables targeted therapeutic interventions (13) .
Several are meanings passing through the imaginary of patients with CKD, from the impact of diagnosis, associated with the recognition of disease severity and treatment, to its consequences, such as the medicinal effects and limits on diet and water habits (14) . Changes in living habits because of illness generate difficulties associated with the absence of experiences that provide pleasure, physical incapacity to perform daily activities, travel to dialysis centers, and changes in working and financial conditions. They also refer to concerns about venous access, water control, and dietary restrictions.
In general, these situations cause doubts, insecurities, fears, anguishes, and sufferings regarding healing and the possibility of living (15) . and data collection steps are described in Figure 1.
The following instruments were used for data collection: 1) Instrument for the characterization of socio-demographic, economic, and clinical data; 2) Instrument of General and Perceived Self-efficacy,  contexts (19) . These instruments were determined as the independent variables of the study.
www.eerp.usp.br/rlae For the analysis of the variable outcome, a regression analysis of the Inflated Beta Model was performed (20) .
The Shapiro-Wilk test was applied to the residuals of the model to verify the hypothesis of their normality.
Confidence intervals with 95% probability were used and the significance level adopted was 5%.   The interpretation is analogous to the other times (Table 2). An increase was observed in the ideal percentage of weight loss of IG patients when compared to CG.
Patients with CKD undergoing hemodialysis treatment who participated in the educational and motivational intervention on fluid intake decreased the pattern of weight gain in interdialytic periods.

Discussion
Education affects the way people behave when facing adversity. Educational practices are effective when they influence the beliefs people have in their own capacities (21) . In this study, the positive impact of an educative and motivational intervention elaborated and implemented for the control of fluid intake for patients with CKD undergoing hemodialysis treatment was observed.
The adequate choice of the tool for the development of this educational intervention, coupled with the adoption of a theoretical reference, was essential for conducting the intervention. In this sense, the theoretical reference should allow the favoring of the teaching-learning process.
The intervention used in this study was elaborated according to Bandura's Social Cognitive Theory (13) .
Patients from IG participated in an educational intervention with the demonstration of a video during the hemodialysis session and dialogues were held to reinforce guidelines on CKD and water intake control.
A study conducted in 2015 aiming at identifying the factors that contribute to the adherence to the diet of patients with CKD undergoing hemodialysis found that 25% of them did not have adherence to the prescribed treatment and that, in 86% of cases, it influences the morbidity and mortality of this population. Age, dialysis time, motivation, and distorted perception of adherence to treatment were factors raised as intrinsic barriers to the adherence to diet and water prescription, while self-efficacy, disease perception, and disease control perception were facilitators of the treatment (22) .
There are still few studies with a theoretical basis in Bandura with regard to patients with CKD. However, international researches have been increasingly interested in the development and use of interventions to promote and support patients in relation to health care (23)(24) .
In health settings, patients report thirst as one of the most prevalent and uncomfortable symptoms, which can overcome all other sensations (25) . When sodium balance is well controlled, thirst mechanism adequately regulates water balance (26) .
Salt intake is a relevant factor in interdialytic weight gain. Patients undergoing hemodialysis treatment receive more fluid in response to the sensation of osmotic thirst, which is usually caused by sodium ingestion (27)(28) .
Immediately after the hemodialysis session, patients may also suffer from volumetric thirst caused by hypovolemia related to the ultrafiltration process (27) .
However, during hemodialysis, there may also be a diffuse sodium transfer to the patient. Some authors attribute an increased thirst in patients with CKD undergoing hemodialysis treatment to sodium dialysate prescription. They state that the diffuse sodium transfer to the patient during hemodialysis contributes to the incomplete removal of sodium and that this problem could be minimized with an individualized prescription of sodium dialysate (29)(30) .
A study carried out with patients undergoing hemodialysis showed that those who underwent hemodialysis sessions with a lower dialytic sodium concentration had a lower interdialytic weight gain and lower blood pressure values. The authors state that changes in sodium dialysate concentration may contribute to a reduction in interdialytic weight gain (31) .
Dietary and dialytic sodium restriction may possibly contribute to decreasing volume overload in patients undergoing hemodialysis (32)(33) . Thus, an adequate sodium balance should compose a goal associated with the control of water intake for these patients.  (34) .
The scarcity of intervention studies with patients with CKD, in particular researches that seeks to investigate water intake control, is evident. Therefore, the educational and motivational intervention used in