What’s New in the Patient Safety World
October 2012
Hyponatremia Predicts Surgical Complications
Over 20 years ago a
group of hospitals in the WNY region collaborated with a local payer to see if
we could predict outcomes in hospitalized patients based on readily available
parameters such as lab test results (unpublished data). At the top of our list
was serum sodium. Hyponatremia was a very good predictor of adverse outcomes in
the hospitalized adult population. Subsequent published studies have
demonstrated hyponatremia is a good predictor of mortality, length of stay and
overall costs.
Now a new study (Leung
2012) shows that preoperative hyponatremia in patients undergoing surgery
predicts higher 30-day mortality and more numerous complications, including
wound infections, perioperative cardiovascular events, and pneumonia. After
adjustment for confounding factors, length of stay in patients with
preoperative hyponatremia is also about a day longer.
Perhaps the most
interesting finding was that the risks were increased the most in patients
undergoing nonemergent surgery and those in the lowest ASA classes, hence patients
who would ordinarily be considered less risky.
The debate is around
whether the hyponatremia is simply a marker of higher risk or is somehow
causally related to the adverse outcomes. Most likely it is simply a marker of
higher risk. Hyponatremia is commonly seen in patients with multiple
comorbidities (including conditions like heart failure, chronic liver or kidney
disease, cancer, etc.) and patients on multiple medications.
Of course, what is not
known is whether correction of the hyponatremia preoperatively reduces these
excess risks. That would require a randomized controlled trial of considerable
magnitude and complexity (since the etiology and management of hyponatremia is
quite diverse).
As we’ve pointed out on numerous occasions, screening for risk factors may be important from a prognostic standpoint but really adds little other than cost if you don’t have interventions that are shown to reduce that excess risk.
References:
Leung AA, McAlister
FA, Rogers SO, et al. Preoperative Hyponatremia and Perioperative
Complications. Arch Intern Med
2012; Published online September 10, 2012
http://archinte.jamanetwork.com/article.aspx?articleid=1357514
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