Sodium gradient, xerostomia, thirst and inter-dialytic excessive weight gain: a possible relationship with hyposalivation in patients on maintenance hemodialysis

PURPOSE: The aim of the study was to assess whether hyposalivation is linked with increased thirst sensation and weight gain in hemodialysis (HD) patients and whether there is any connection between hyposalivation and sodium balance. METHODS: One hundred and eleven participants (64 males and 47 females) receiving maintenance hemodialysis, mean age 59.1 ± 13.6 years old, were involved in the study. All participants completed a survey evaluating thirst intensity (DTI) and xerostomia inventory (XI). In addition, pre-dialysis sodium concentration and inter-dialytic weight gain (IWG) were assessed. The division into no-hyposalivation and hyposalivation groups was based on an unstimulated whole saliva (UWS) flow rate. RESULTS: Hyposalivation, UWS below 0.1 mL/min, was reported in 28.8 % of HD patients. In these participants, IWG was higher than in patients with UWS > 0.1 mL/min (3.65 ± 1.78 vs 3.0 ± 1.4; p = 0.042), as well as the pre-dialysis sodium gradient (3.22 ± 2.1 vs 1.6 ± 2.8; p = 0.031). The mean XI and DTI scores did not differ between study groups. In the hyposalivation group, pre-dialysis sodium serum gradient negatively correlated with saliva outflow (ρ = −0.61, p = 0.019) and positively with IWG (ρ = 0.49, p = 0.022). IWG correlated with XI (ρ = 0.622, p = 0.016) in hyposalivation group and with DTI in no-hyposalivation group (ρ = 0.386, p = 0.033). CONCLUSIONS: Hyposalivation significantly correlates with IWG; however, its influence on thirst and self-reported mouth dryness seems to be weaker than expected. Additionally, hyposalivation was found to be associated with an elevated pre-dialysis sodium gradient.