Unveiling the Patterns of Water Diuresis in Profound Hyponatremia Management in Intensive Care Unit Settings

Key Points Water diuresis presents a conundrum during the treatment of profound hyponatremia, but its clinical characteristics remain unclear. This study revealed that water diuresis mostly manifests within 24 hours of treatment, preceded by changes in urinary characteristics. Careful urine monitoring in the early stages of hyponatremia treatment could facilitate the early detection of water diuresis. Background Hyponatremia treatment guidelines recommend avoiding excessive increases in serum sodium concentration (s[Na]) to prevent osmotic demyelination syndrome. Although an unexpected rise in s[Na] has been attributed to water diuresis during the treatment of hyponatremia, clinical courses of water diuresis are unclear. We conducted this study to investigate the clinical characteristics of water diuresis during profound hyponatremia management. Methods In this retrospective observational study, we examined patients with profound hyponatremia (s[Na] ≤120 mEq/L) admitted to the intensive care unit of a Japanese hospital. The manifestation of water diuresis was defined as a urine volume (UV) ≥2 ml/kg per hour and a urinary sodium plus potassium concentration (u[Na+K]) ≤50 mEq/L. We analyzed changes in UV and u[Na+K] over time for patients experiencing water diuresis. This analysis employed a mixed-effects model with spline terms for time, and the results are graphically presented. Results Among 47 eligible patients, 30 (64%) met the criteria for water diuresis. The etiologies of hyponatremia were drug-related hyponatremia ( n =10; 33%), primary polydipsia ( n =8; 27%), hypovolemic hyponatremia ( n =7; 23%), syndrome of inappropriate antidiuresis ( n =7; 23%), and acute heart failure ( n =1; 3%). Among patients with water diuresis, 27 (90%) experienced the manifestation of water diuresis within 24 hours after the start of correction. The increased UV and decreased u[Na+K] levels began several hours before the peak manifestation of water diuresis. Within 6 hours after the manifestation of water diuresis, 29 patients (97%) received electrolyte-free infusions and 14 (47%) received desmopressin. One patient (3%) with water diuresis experienced overcorrection. Conclusions Water diuresis is common during the treatment for profound hyponatremia and typically occurs within the first 24 hours, preceded by changes in urinary characteristics. Early detection and prompt response to water diuresis through urine monitoring during the early periods of hyponatremia treatment may be effective for managing water diuresis.