Fluid Intake Management in Maintenance Hemodialysis Using a Smartphone-Based Application: A Pilot Study

Rationale & Objective: Increased interdialytic weight gain (IDWG) has been associated with increased morbidity and mortality. We evaluated the usefulness and safety of a mobile application (app) that allows patients receiving maintenance hemodialysis to self-monitor their daily fluid intake. Study Design: Within group comparison before or during intervention. Setting & Participants: Patients receiving maintenance hemodialysis with mean IDWG of <4%. Exposure: Participants were trained to use a smartphone-based app, FiApp that allowed them to record fluid intake and compare with individual targeted daily fluid intake determined by the nephrologist. Outcomes: The primary study outcome was the association between IDWG and fluid intake recorded in the FiApp. Secondary outcomes included FiApp safety and usage. Patient interviews were performed at weeks 1 and 4 to collect information regarding FiApp usability and recommendations for app improvements. Analytical Approach: Mean, median, and standard deviation. Results: Eighteen of 25 patients completed the full 4-week study, provided all app data, and completed 2 patient interviews. The mean 4-week IDWG during app use was similar to the baseline mean 4-week IDWG before app use; however, 61% of the participants had a decrease in IDWG when using the app compared with IDWG at baseline. Of the 18 participants who completed the study, only 1 had a mean 4-week IDWG that was 20% higher than that at baseline. The app was used on ≥80% of the days by 13 (72%) of 18 participants, and was used every day in 7 (39%) of 18 participants. The mean relationship between fluid reported in the app and fluid consumed was 40%. Limitations: This safety study recruited patients who had IDWG of <4%. Conclusions: A smartphone-based app can be safely used to help patients receiving maintenance hemodialysis track and control fluid intake. Motivated patients were able to decrease IDWG despite baseline IDWG being <4% of the body weight. Trial Registration: NCT03759847. Plain-Language Summary: Patients receiving maintenance hemodialysis struggle to limit fluid intake. Excess fluid intake can lead to adverse cardiovascular events. We developed a smartphone app to help patients receiving dialysis self-monitor their fluid intake. In this safety study in patients receiving dialysis with an interdialytic weight gain of <4% of the body weight, more than half of the patients were able to decrease their interdialytic fluid intake while using the app, and only 1 patient had an increase in interdialytic weight gain of >20% while using the app. Information gleaned from structured patient interviews will be used to refine this app.