Hyponatremia Associated with Worse Outcomes Following Cardiac Surgery

To study the association between postoperative hyponatremia and mortality, length of hospital stay (LOS), and complications, the authors of “Postoperative Hyponatremia Predicts an Increase in Mortality and In-Hospital Complications after Cardiac Surgery,” published in Journal of the American College of Surgeons, studied outcomes from 4,850 patients who underwent cardiac surgery.

They found that 59% of patients experienced postoperative hyponatremia. These patients tended to have lower left ventricle ejection fraction, higher mean pulmonary artery pressures, lower glomerular filtration rate, higher EuroSCORE, and were more likely to be New York Heart Association class IV.

Hyponatremic patients in the study also had a higher prevalence of COPD, and peripheral vascular disease.

Patients with hyponatremia experienced increased overall and late mortality rates, with mortality rates increasing with the severity of the hyponatremia.

They also spent more time in the hospital (average length of stay of 11 days vs. 7 days for non-hyponatremic patients).

The authors reported that, after adjusting for baseline and procedure variables, “postoperative hyponatremia was associated with increase in mortality (hazard ratio 1.22, 95% CI 1.06—1.4, p = 0.004), LOS (multiplier 1.34, 95% CI 1.22–1.49, p < 0.001), infectious (odds ratio [OR] 2.32, 95% CI 1.48–3.62, p < 0.001), pulmonary (OR 1.82, 95% CI 1.49–2.21, p < 0.001), and renal failure complications (OR 2.46, 95% CI 1.58–3.81, p < 0.001) and need for dialysis (OR 3.66, 95% CI 1.72–7.79, p = 0.001).

Based on these results, the author concluded that “hyponatremia is common after cardiac surgery and is an independent predictor of increased mortality, length of hospital stay, and postoperative complications.”