Successful treatment of chronic alcohol-induced refractory hyponatremia with tolvaptan: a case report with in-depth analysis of traditional treatment failure mechanisms.

Background: Hyponatremia associated with the syndrome of inappropriate antidiuretic hormone secretion (SIADH) induced by chronic alcoholism exhibits high treatment resistance. The mechanisms underlying traditional treatment failure are often overlooked in clinical practice. Case Presentation: We report a case of a 59-year-old male patient with a 30-year history of heavy alcohol consumption, presenting with persistent serum sodium levels below 130 mmol/L for 3 months (nadir 116 mmol/L). Despite 3 months of aggressive sodium supplementation and fluid restriction therapy, serum sodium fluctuated between 116 and 125 mmol/L. Laboratory investigations revealed plasma ADH of 42 pg/mL (normal <5 pg/mL), plasma osmolality of 242 mOsm/kg, and urine osmolality of 486 mOsm/kg, consistent with SIADH diagnosis. Key Observations: Traditional treatment failure demonstrated a distinctive pattern: paradoxical increase in urine output during fluid restriction (intake 800 mL vs. urine output 1,200-1800 mL); paradoxical decrease in serum sodium following sodium supplementation (130→116 mmol/L) with compensatory increase in urinary sodium excretion (60→100 mmol/L); spironolactone increased urinary sodium excretion but serum sodium continued to decline. Intervention and Outcome: Treatment was switched to oral tolvaptan 15 mg once daily. Serum sodium increased to 128 mmol/L within 48 h and normalized to 135-138 mmol/L by day 7, with a correction rate of 8-9 mmol/L/24 h (within safe limits). No osmotic demyelination syndrome occurred. At 3-month follow-up, serum sodium remained stable within normal range. Novelty: This report provides the first systematic analysis of the specific resistance mechanisms of alcohol-induced SIADH to traditional treatment, revealing the molecular mechanisms underlying the "sodium paradox" (sodium supplementation paradoxically worsening hyponatremia), including V2 receptor upregulation leading to excessive water reabsorption, impaired hepatic ADH inactivation, and excessive compensatory renal sodium excretion. Conclusion: Tolvaptan demonstrates rapid, effective, and controllable therapeutic effects in alcohol-related refractory hyponatremia. This case emphasizes the importance of ADH measurement and pathophysiological mechanism analysis in such patients, providing a foundation for individualized treatment decisions.