Dehydration in the Dying Process: An Integrative Systematic Review of Physiological Mechanisms and Clinical Implications

Dehydration is a common finding in patients with life-limiting illnesses at the end of life. Clinicians often face uncertainty when deciding on the use of artificial hydration, particularly given concerns about thirst, delirium, and respiratory secretions. Despite its clinical relevance, the underlying physiology of terminal dehydration has been insufficiently explored. We conducted an integrative systematic review of studies addressing dehydration in patients with advanced disease at the end of life. Six databases were searched up to March 2025. Eligible studies included physiological or clinical analyses of dehydration in terminally ill populations. Seven studies met inclusion criteria. Evidence suggests that terminal dehydration often reflects a regulated, adaptive process rather than a simple fluid deficit. Laboratory findings showed stable electrolytes and activation of the renin–angiotensin–aldosterone system, with minimal association between biochemical changes and thirst. Bioelectrical impedance indicated progressive intracellular dehydration consistent with catabolic decline. Clinically, higher hydration volumes correlated with increased risk of respiratory secretions, edema, and agitation, while reduced hydration was associated with improved comfort and fewer secretion-related complications. Terminal dehydration appears to be an adaptive physiological response in dying patients, with limited evidence of symptomatic benefit from artificial hydration and potential for harm.