For decades, it’s been standard practice in hospitals throughout the United States for physicians to treat patients using intravenous (IV) fluids.

“It’s probably the most common intervention that hospitalized patients receive and it’s been part of medicine for more than a hundred years — but it hasn’t received quite as much attention as other aspects of medicine,” Dr. Matthew Semler, assistant professor of Medicine at Vanderbilt University School of Medicine in Tennessee, told Heathline.

During this time, there have generally been two choices when it comes to intravenous fluids.

One is a saline solution, which contains high concentrations of sodium chloride.

The other is a balanced crystalloid solution that more closely mimics plasma, the liquid part of blood.

While both solutions are widely available and share a similar price point, the saline solution tends to be used more.

This could change, however, given a pair of recent studies that sound the alarm over saline solution, touting the balanced solution as a better intervention.

One study is authored by Semler. The other is authored by Dr. Wesley Self, also of Vanderbilt University.

Both were published in The New England Journal of Medicine earlier this month.

In both cases, the researchers say the results are clear.

They say the balanced fluid has better patient outcomes, while the saline solution is more likely to cause kidney problems.

With millions of patients receiving IV treatment every year, Semler says it just makes sense for health professionals to make the switch to the balanced solution.

“Early research in animal models, observational studies in patients, and early small studies suggested that actually there might be the possibility that saline, the most common fluid, might have effects on the kidney,” said Semler. “So that’s what prompted the study, was the idea that this very common intervention that millions of patients receive each year, might actually be better with this similarly priced, inexpensive alternative.”

Grandfathered in

When it comes to age-old medical interventions such as IV treatment, the practice is often older than the regulatory watchdogs that monitor medicine.

“A lot of things in medicine came about in an era before we required rigorous control,” explained Semler. “These IV fluids were invented before the FDA. They were common in practice before medicine had to be approved, so they’ve kind of been grandfathered in.”

With limited resources, regulators and companies tend to focus more on newer technologies and treatments, letting the exploration of older interventions like IV treatment fall by the wayside.

Semler says it’s important to take a closer look at some of these common therapies to find ways they could be improved.

“It’s not always about [studying] a million-dollar new drug. It’s also our responsibility to study the common stuff,” he said. “That’s been a focus for our group, is to try and focus on the things that are common — the things that are so routine that we don’t really think about them in our daily practice.”

Small differences add up

Both studies found that the chance of serious kidney problems or death was about 1 percent lower with the balanced fluid.

They noted the high concentration of salt in saline fluid can cause kidney problems.

While the 1 percent difference might not sound like a lot, it adds up given the ubiquity of IV intervention.

“Our study shows a little difference between groups, and so one of the things people have asked us is, ‘Is that important?’” says Semler. “Unlike a new cancer drug, where it applies to a very small group of patients at a very high cost, these results are the opposite in that there are more than five million patients in the United States in the intensive care unit who receive fluids each year. So even a tiny difference in outcomes for an intervention that nearly all patients receive has big implications.”

While changing hearts and minds across the country will likely take time, the studies have already led to changes in the way that some doctors are treating patients.

At Vanderbilt, where saline was typically the solution of choice for IV treatment, doctors are now being encouraged to switch to the balanced solution.

“Our pharmacy and therapeutics committee voted unanimously to switch to primarily using balanced crystalloids,” explained Semler. “This is because the barriers aren’t huge. The fluids are similar in cost, and big manufacturers make both types. So, it’s mostly been, for us, about talking with clinicians about the findings, starting to stock our wards with balanced crystalloids primarily instead of saline.”

“Findings for one individual patient might not look huge, but when applied on a larger scale, have some really big implications,” he added.