ESA-SRB-AOTA 2019

Introduction:

Hyponatremia is the most common electrolyte disorder in clinical practice which affects 15-20% of hospitalised patients with significant clinical and economic burden. The most common cause of hyponatremia is syndrome of inappropriate ADH (SIADH), characterised by euvolemia with relatively high urine osmolality compared to serum osmolality. Treatment of hyponatremia is controversial with fluid restriction being the first line treatment for SIADH. Tolvaptan is an antagonist to vasopressin type 2 receptors in the renal collecting duct which has been recommended as the second line treatment for euvolemic or hypervolemic hyponatremia.

Aim:

The aim is to determine the efficacy and cost effectiveness of inpatient tolvaptan use and help guide future treatment of hyponatremia.

Material and methods:

This is a retrospective case series of patient who received tolvaptan for treatment of hyponatraemia at Eastern Health. The medical records of patients were used to obtain data.      

Results:

Eight patients received tolvaptan at Eastern Health in 2018 and 2019. The average age of patients was 85 years with average length of stay of 19 days. Three patients needed ICU admission due to severe hyponatremia. Treatment with 7.5mg or 15mg of tolvaptan was started after a trail of fluid restriction for five days on average. The serum sodium increased from an average of 124mmol/l on admission to 133mmol/l on discharge after an average of two days of tolvaptan (table 1). Two patient had sodium overcorrection of more than 10mmol/l over 24 hours and one received IV dextrose. All patients were symptomatic with their hyponatremia, and one remained symptomatic with residual fatigue after tolvaptan (table 2). 

Conclusion

Tolvaptan is an effective treatment of hyponatremic patients. At the cost of $16.21 per 15mg dose, it could be potentially cost saving due to reduced length of hospital stay and avoidance of ICU admissions in these complex patients.