Severe hyponatraemia in elderly hospitalized patients: prevalence, aetiology and outcome

Evaluation of costs associated with tolvaptan-mediated hospital length of stay reduction among US patients with the syndrome of inappropriate antidiuretic hormone secretion, based on SALT-1 and SALT-2 trials

BACKGROUND

Two randomized clinical trials, the Study of Ascending Levels of Tolvaptan in Hyponatremia 1 and 2 (SALT-1 and SALT-2), showed that tolvaptan was an efficacious and safe therapy for the treatment of hyponatremic patients with the syndrome of inappropriate antidiuretic hormone secretion (SIADH).

HYPOTHESIS

This study evaluated the potential cost savings associated with tolvaptan usage based on the SALT-1 and SALT-2 trials.

METHODS

Hospital length of stay (LOS) reduction associated with tolvaptan versus placebo was evaluated among hyponatremic patients with the SIADH (serum sodium < 135 mEq/L) from the combined data of the SALT-1 and SALT-2 trials. The Healthcare Cost and Utilization Project 2009 Nationwide Inpatient Sample database was used to estimate hospital cost and LOS for hospitalizations of adult (age ≥ 18 years) patients with the SIADH. A cost-offset model was constructed to evaluate the impact of tolvaptan on hospital cost and LOS, with univariate and multivariate Monte Carlo sensitivity analyses.

RESULTS

In the SALT-1 and SALT-2 trials, patients with the SIADH receiving tolvaptan had a shorter hospital LOS than patients receiving placebo (4.98 vs 6.19 days, respectively). There were 21 718 hospitalizations for the SIADH identified from the Healthcare Cost and Utilization Project Nationwide 2009 Inpatient Sample database, with a mean LOS of 5.7 days and mean total hospital costs of $8667. Using an inpatient tolvaptan treatment duration of 4 days, with a daily wholesale acquisition cost of $250, the cost-offset model estimated an LOS reduction among SIADH hospitalizations of 1.11 days. The total cost offset, including tolvaptan drug cost, was estimated to be $694 per admission. The cost-neutral break-even duration of tolvaptan therapy is 6.78 days. Univariate and multivariate sensitivity analyses demonstrated consistent cost reduction associated with tolvaptan usage. Ten thousand cycles of Monte Carlo simulation showed the 95% CI for cost offset to be $73 to $1405.

CONCLUSION

Based on the SALT-1 and SALT-2 trials, tolvaptan usage is associated with a shorter hospital LOS than placebo among patients with the SIADH. Including the drug cost for 4 days of inpatient tolvaptan therapy, tolvaptan is associated with an estimated mean hospital cost reduction of $694 per admission in the United States.

Cost Issues in Hyponatremia

Purpose

To describe the morbidity and mortality associated with hyponatremia and its impact on health care costs and outcomes in the United States, describe the role of pharmacists in the overall management of hyponatremia, and identify and address cost and resource allocation issues.

Summary

Hyponatremia places a significant burden on overall hospital and health care costs. Underrecognition of the disorder and inappropriate hospital management can lead to worse outcomes, impacting length of stay (LOS), need for intensive care unit (ICU) admission, and clinical outcomes. Risk of mortality rises with increasing severity of hyponatremia, but even mild hyponatremia is associated with increased in-hospital mortality. The association with mortality is particularly robust in patients admitted to the hospital with cardiovascular disease and metastatic cancer. For patients admitted to the ICU, severe hyponatremia is a predictor of mortality. Elderly patients with admission hyponatremia face an especially poor prognosis. Resolving hyponatremia during hospitalization decreases the risk of mortality, suggesting that improved identification and aggressive monitoring may lead to more appropriate treatment. Pharmacoeconomic data can be utilized to support clinical decision-making in the management of hyponatremia by evaluating drug therapy and by monitoring hyponatremia development and therapeutic outcomes.

Conclusion:

Prompt recognition and optimal management of hyponatremia in hospitalized patients may reduce mortality and symptom severity, allow for less intensive care, decrease LOS and associated costs, and improve treatment of underlying comorbid conditions and quality of life. Pharmacists have a key role in optimizing the management of hyponatremia.