Low Salt DIet + Diuretics = Problems!

Salt restrictive diets when adopted in conjunction with diretic drug therapy can significantly increase the risk of hospitalization and death in people with moderate to severe heart failure, according to a new systematic review of six trials representing more than 2,700 patients.

Clinicians commonly recommend salt restriction for people with heart failure; some advise patients to limit intake to less than 2 grams per day, especially in severe cases. This is in keeping with the 2010 guidelines from the Heart Failure Society of America. But these recommendations are based largely on observational data, and recently, researchers have begun to question the wisdom of salt restriction.

A Cochrane review in 2011 identified a single randomized trial evaluating low sodium diets in patients with heart failure taking high-dose furosemide, and found an association between low sodium and increased mortality.

The new systematic review, published in this month's edition of the journal, Heart, compared low sodium versus normal sodium diets in 6 randomized trials representing 2,747 patients with heart failure. The patients in these studies were on a broad range of diuretic drug regimens.

In all trials, patients were randomized to a low-sodium diet of 1.8 grams daily vs. a normal sodium diet of 2.8 grams daily. Most trials had a fluid restriction for all patients of 1 liter daily. Furosemide doses (IV or oral) ranged from a low of 50-125 mg twice daily in 1 trial with 1,771 patients to a high of 500-1000 mg twice daily in 2 trials.

Compared to normal sodium diets, low sodium diets significantly increased all-cause mortality (risk ratio [RR] 1.95, 95% CI 1.66-2.29), heart failure-related mortality (RR 2.23, 95% CI 1.77-2.81) and heart failure readmissions (RR 2.1, 95% CI 1.67-2.64) (level 1 [likely reliable] evidence). The numbers needed to harm (NNH) were 6-12 for all-cause mortality and 2-7 for readmission. Low sodium diets were also associated with increased risk of sudden death (RR 1.72, 95% CI 1.21-2.44).

In the largest trial, with the most clinically applicable furosemide dosing, the low sodium diet was associated with increased mortality (23.8% vs. 12.9%, p < 0.0001, NNH 9) and increased heart failure readmissions (34.2% vs. 18.5%, p < 0.0001, NNH 6) in follow-up of 57 months. In this trial, the normal sodium group received hypertonic saline solution 150 mL with each furosemide infusion.

Thanks to our friends at DynaMed for pointing out this important systematic review.