JUAN CRESTANELLO: Welcome to the Cardiovascular Surgery Series, where we'll review the latest research in cardiovascular surgery from the Mayo Clinic in just two minutes. My name is Juan Crestanello, and I am a cardiac surgeon at the Mayo Clinic in Rochester, Minnesota. We will discuss today hyponatremia, an overlooked risk factor associated with adverse outcomes after cardiac surgery. This article was published in the Annals of Thoracic Surgery in July 2021.

In this article, we analyze the prevalence and outcomes of patients with preoperative hyponatremia in more than 16,000 patients undergoing cardiac surgery. Hyponatremia was defined as serum sodium less than 135 milliequivalents per liter. Preoperative hyponatremia was present in 10% of the patients.

Patients with hyponatremia had more comorbidities, and hyponatremia was independently associated with an increased risk of operative mortality, an increased rate of operative complications, and an increased long-term mortality.

When we analyze hyponatremia as a continuous variable, the severity of hyponatremia was also associated with increased risk of death and operative complications. We conclude that preoperative sodium is a powerful variable to risk stratify patients before cardiac surgery beyond the traditional risk stratification systems.

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