What’s in That IV Bag? Don’t Use Saline, Studies Suggest

Balanced fluids slightly reduce deaths, kidney problems in large studies

Two new studies suggest that patients do better when providers switch from using intravenous saline therapy to balanced fluids that closely resemble the liquid part of blood.

Vanderbilt University Medical Center researchers believe the studies could improve survival and decrease kidney complications. Saline, used in medicine for more than a century, contains high concentrations of sodium chloride, which is similar to table salt.

“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,” said study author Matthew Semler, MD, Assistant Professor of Medicine at Vanderbilt University School of Medicine. “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.”

The Vanderbilt research, published February 27 in the New England Journal of Medicine, examined more than 15,000 intensive care unit (ICU) patients and more than 13,000 emergency department (ED) patients who were assigned to receive saline or balanced fluids if they required intravenous (IV) fluid. 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,” said study author Wesley Self, MD, MPH, Associate Professor of Emergency Medicine. “When we say a 1% reduction, that means thousands and thousands of patients would be better off.”

The authors estimate this change could lead to at least 100,000 fewer patients suffering death or kidney damage each year in the United States.

Conducted between June 2015 and April 2017, the studies involved use of the electronic health record to direct patient care, monitor outcomes, and compile the findings.

One study compared balanced crystalloids (lactated Ringer’s solution or Plasma-Lyte A) with saline among 13,347 adults who were treated with IV crystalloids in the ED and subsequently hospitalized outside an ICU. The type of crystalloid that was administered in the ED was assigned to each patient on the basis of calendar month, with the entire ED crossing over between balanced crystalloids and saline monthly during the 16-month trial. The number of hospital-free days (days alive after discharge before day 28) did not differ between the balanced-crystalloids and saline groups. However, balanced crystalloids resulted in a lower incidence of major adverse kidney events within 30 days than saline (4.7% versus 5.6%).

In the second study, conducted in five ICUs, 15,802 adults received saline or balanced crystalloids according to the randomization of the unit to which they were admitted. Among the 7,942 patients in the balanced-crystalloids group, 1,139 (14.3%) had a major adverse kidney event, compared with 1,211 of 7,860 patients (15.4%) in the saline group. In-hospital mortality at 30 days was 10.3% in the balanced-crystalloids group and 11.1% in the saline group. The incidence of new renal-replacement therapy was 2.5% and 2.9%, respectively, and the incidence of persistent renal dysfunction was 6.4% and 6.6%, respectively.

Sources: Vanderbilt University; February 27, 2018; NEJM, February 27, 2018; NEJM, February 27, 2018.