Serum Sodium Fluctuations Predict In-Hospital, Post-Discharge Mortality in Acute Pulmonary Embolism Patients

While baseline hyponatremia has been shown to predict mortality within a month of acute pulmonary embolism, fluctuations in serum sodium levels and their impact on acute and long-term outcomes in patients presenting the venous thromboembolic disease haven’t been established.

In order to find out if transient hyponatremia predicts mortality in the short term and beyond, a group of Australian researchers tracked the outcomes of 773 patients who were admitted to Concord Repatriation General Hospital in Sydney with confirmed acute pulmonary embolism between January 2000 and December 2007.

In their “Fluctuation of Serum Sodium and Its Impact on Short- and Long-Term Mortality Following Acute Pulmonary Embolism” analysis published online in the April 2013 edition of PLOS One, Austin Chin Chwan Ng, MD, of the Concord Clinical School at the University of Sydney, and colleagues divided the cohort into four groups according to broad patterns of serum sodium fluctuation: normonatremia (n=605), corrected hyponatremia during hospital admission (n=58), acquired hyponatremia during hospital admission (n=54), and persistent hyponatremia (n=56).

Though the combined in-hospital mortality was only 3.2 percent, the researchers noted a greater percentage of acute pulmonary embolism patients in the corrected and persistent hyponatremia groups died in Concord Hospital compared to patients with normonatremia, while no in-hospital deaths occurred in the acquired hyponatremia group. Taking the 275 patients who died post-discharge into account, the authors found significantly worse long-term survival in the acquired and persistent hyponatremia groups compared to the normonatremic patients, and they ultimately recorded a total mortality of 38.8 percent.

After breaking down each groups’ share in terms of both short- and long-term mortality, the authors discovered “those presenting with normal serum sodium level that is maintained during admission had the best in-hospital survival, (and) for patients who survived to hospital discharge, those with initial hyponatremia that was corrected during admission had similar long-term survival to normonatremia patients, while patients who acquired hyponatremia during admission or had persistent hyponatremia had the worst long-term survival.”

Based on those findings, the researchers recommended “at the very least, those patients with hyponatremia on discharge should be considered as warranting careful long-term surveillance” that could include follow-up assessments on hypothyroidism, adrenal insufficiency, iatrogenic hyponatremia, and unrecognized heart failure, which are all potential contributing factors to persistently low serum sodium levels.

Though their research supplied evidence of serum sodium fluctuations predicting short- and long-term outcomes after acute pulmonary embolism, the authors called for further clinical investigation on the factors mediating hyponatremia correction.