Preoperative hyponatremia increases the risk of death within 30 days of surgery, according to a new study.

The study of 964,263 adults who underwent major surgery showed that the 30-day mortality risk was 5.2% for patients with preoperative hyponatremia compared with 1.3% for patients without preoperative hyponatremia, a difference that translated into a 44% increased risk, after adjusting for potential confounders.

In addition, preoperative hyponatremia was associated with an increased likelihood of perioperative major coronary events (1.8% vs. 0.7%), wound infections (7.4% vs. 4.6%), and pneumonia (3.7% vs. 1.5%).

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The study, by Alexander A. Leung, MD, of Brigham and Women’s Hospital in Boston, and colleagues, was published online in Archives of Internal Medicine.

Of the 964,263 subjects, 75,423 (7.8%) had preoperative hyponatremia, which the investigators defined as a sodium level below 135 mEq/L).

“Although this study provides evidence that preoperative hyponatremia is associated with perioperative morbidity and mortality, further research is needed to establish whether correcting preoperative hyponatremia will mitigate risks,” the authors stated.

Hyponatremia has been linked to increased morbidity and mortality in a variety of medical conditions but its association with perioperative outcomes is uncertain, the authors noted in their report.