HelixTalk Episode #120 - When it Rains it Pours: A Succinct Clinical Review of Hyponatremia due to SIADH

Date posted: October 13, 2020, 6:00 am

In this episode, we discuss the pathophysiology, drug-related causes, diagnosis, and treatment of a common type of hyponatremia called the syndrome of inappropriate antidiuretic hormone (SIADH).

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Key Concepts

1. SIADH causes hyponatremia by causing the body to reabsorb too much water and making the urine too concentrated. The core pathophysiology is a problem with water handling that leads to a sodium problem.
2. SSRIs are the most common drug-induced cause of SIADH.  Other commonly implicated drugs are carbamazepine, oxcarbazepine, high-dose cyclophosphamide, and a variety of other CNS-acting medications.
3. In acute or severe hyponatremia, 3% NaCl (hypertonic saline) is used to quickly increase serum sodium by about 6 mEq/L to avoid neurologic complications of hyponatremia.
4. Fluid restriction (about 1-1.5 L/day) is the first-line therapy of SIADH management.  It takes several days for serum sodium to return back to normal levels.

References

• Cuzzo B, Padala SA, Lappin SL. Vasopressin (Antidiuretic Hormone, ADH) [Updated 2020 Apr 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK526069/
• Verbalis JG, Goldsmith SR, Greenberg A, et al. Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations. Am J Med. 2013;126(10 Suppl 1):S1-S42. doi:10.1016/j.amjmed.2013.07.006