Two studies by Vanderbilt University Medical Center researchers show that using saline as IV fluid therapy creates a higher risk of kidney complications for most patients.

Saline contains high concentrations of sodium chloride. Vanderbilt researchers found patients do better if, instead, they are given a lactate equal to blood alkali content-balanced fluids that closely resemble the liquid part of blood.

“Our results suggest that using primarily balanced fluids should prevent death or severe kidney dysfunction for hundreds of Vanderbilt patients and tens of thousands of patients across the country each year,” Matthew Semler, MD, MPH, assistant professor of medicine at Vanderbilt University School of Medicine and a co-author of one of the papers published by the New England Journal of Medicine, said in a press release. “Because balanced fluids and saline are similar in cost, the finding of better patient outcomes with balanced fluids in two large trials has prompted a change in practice at Vanderbilt toward using primarily balanced fluids for intravenous fluid therapy.”

In the studies, more than 15,000 patients in intensive care and more than 13,000 patients in EDs were assigned in five ICUs at an academic center to receive either saline or balanced fluids if they required IV fluid.

“The primary outcome was the proportion of patients who met one or more criteria for a major adverse kidney event within 30 days — the composite of death, new receipt of renal-replacement therapy, or persistent renal dysfunction (defined as a final inpatient creatinine value ≥ 200% of the baseline value) — all censored at hospital discharge or 30 days after enrollment, whichever came first,” the authors wrote in their papers.

Among the 7,942 patients in the balanced-fluids group, the press release noted that 14.3% had a major adverse kidney event compared with 15.4% of patients in the saline group. In-hospital mortality at 30 days was 10.3% in the balanced-fluids group and 11.1% in the saline group. The incidence of new renal-replacement therapy was 2.5% in the fluids group and 2.9% in the saline group, and the incidence of persistent renal dysfunction was 6.4% in the fluids group and 6.6% in the saline group.

In both studies, the incidence of serious kidney problems or death was about 1% lower in the balanced fluids group compared to the saline group.

“The difference, while small for individual patients, is significant on a population level. Each year in the United States, millions of patients receive intravenous fluids,” Semler said in the release. “When we say a 1% reduction that means thousands and thousands of patients would be better off,” he said.

The authors estimate this change may lead to at least 100,000 fewer patient deaths or having kidney damage each year in the United States.

“With the number of patients treated at Vanderbilt every year, the use of balanced fluids in patients could result in hundreds or even thousands of fewer patients in our community dying or developing kidney failure,” study co-author Todd Rice, MD, MSc, associate professor of medicine, said in the release. “After these results became available, medical care at Vanderbilt changed so that doctors now preferentially use balanced fluids.”