Thirst in patients on chronic hemodialysis: What do we know so far?

Thirst has been defined as "the sensation that leads animal's and human's actions toward the goal of finding and drinking water" or as "any drive that can motivate water intake, regardless of cause". Thirst, together with xerostomia, is the main cause of poor adherence to fluid restriction and of excessive intake of fluids in patients on chronic hemodialysis, and consequently of high interdialytic weight gain. Interdialytic weight gain (IDWG) should be lower than 4.0-4.5% of dry weight. Unfortunately, many patients have an IDWG greater than this value and some have IDWG of 10-20%. High IDWG is associated with a higher risk of all-cause and cardiovascular death and increased morbidity, such as ventricular hypertrophy and major adverse cardiac and cerebrovascular events. In addition, high IDWG leads to supplementary weekly dialysis sessions with consequent deterioration of quality of life and increased costs. Thus, the knowledge of thirst in patients on chronic hemodialysis is essential to prompt its adequate management to limit IDWG in the routine clinical practice. The present review aims to describe the physiology of thirst in patients on chronic hemodialysis, as well as the prevalence, its measures, the associated variables, the consequences, and the strategies for its reduction.