Ingrid Hein

November 02, 2017

TORONTO — Hospitalized patients who receive balanced crystalloid fluids, whether they are critically ill or not, are about 1% less likely to need renal replacement therapy, have persistent renal dysfunction, or die in the hospital than patients who receive saline, two new landmark studies show.

"This has population-wide implications," said Matthew Semler, MD, from Vanderbilt University Medical Center in Nashville, Tennessee.

"These fluids are administered to more than 5 million ICU patients, so a difference of 1% translates to thousands of new renal replacement therapies, persistent renal dysfunction, and deaths," he said here at CHEST 2017.

Sepsis is the most common cause of death in the hospital, and "this could have a particularly large implication for those patients," he told Medscape Medical News. "But the effects were not limited to that group."

The fact that saline increases chloride levels more than balanced crystalloids is likely the prime factor, Dr Semler explained. "There has been a hypothesis that balanced crystalloids are more aligned with human blood, and there were theories about why that might be better for use in humans. Now we can support those."

In the Isotonic Solutions and Major Adverse Renal Events Trial (SMART), 15,802 adults treated in five ICUs at a single academic center were assessed.

This has population-wide implications.

In the cluster-randomized multiple crossover trial, the five ICUs swapped saline and balanced crystalloids on even and odd months. Over the study period of slightly more than 16 months, 7860 patients received 0.9% sodium chloride and 7942 received Ringer's lactate solution or Plasma-Lyte A.

The primary outcome of the trial was major adverse kidney events within 30 days, defined as death, new renal replacement therapy, or persistent renal dysfunction (a doubling of creatinine from baseline) in the 30 days after administration and before hospital discharge.

Patients who received balanced crystalloids were more likely to meet the primary outcome than those who received saline (14.3% vs 15.4%; adjusted odds ratio [OR], 0.90; P = .04). And there were fewer in-hospital deaths in the crystalloid group than in the saline group (10.3% vs 11.1%; adjusted OR, 0.90; P = .06)

"The results show that patients using balanced crystalloids had a 1.1% absolute decrease in death, new renal replacement therapy, or persistent renal dysfunction," Dr Semler reported.

This translated into a number needed to treat of 94 people, meaning that switching from saline to balanced crystalloids would prevent one patient from experiencing death, new renal replacement therapy, or persistent renal dysfunction for every 94 patients treated.

"Among patients with sepsis, in-hospital mortality was 25.2% with balanced crystalloids and 29.4% with saline," Dr Semler told Medscape Medical News.

We saw the same results in mildly ill patients all the way through to very critically ill patients.

A second study with a methodology similar to SMART looked at 13,347 patients who were not critically ill and were treated in the emergency department at the same academic center.

As in SMART, patients who received balanced crystalloids were more likely to meet the primary outcome than those who received saline (4.7% vs 5.6%; adjusted OR, 0.82; P = .01).

"The difference was about 1% in both studies," said Wesley Self, MD, from Vanderbilt University, who was lead investigator on the second study.

"We saw the same results in mildly ill patients all the way through to very critically ill patients," he explained, which is one of the reasons this has broad implications.

These findings really emphasize the importance of using rigorous scientific methods to study things we have grandfathered into practice, Dr Self explained. "This is something we've never really been able to detect before, with all the noise from clinical practice."

That's a phenomenal impact with a very low-tech solution.

"This is such a beautifully planned clinical trial," Ben deBoisblanc, MD, from Louisiana State University in New Orleans, said after the presentation. "This is what we need to do to answer some of these fundamental clinical questions."

"I think you understated the effect of this trial. It's a small number — 1% — but it's cheap," he said. "That's a phenomenal impact with a very low-tech solution."

Saving Money in the Long Run

"This study adds to the swelling body of information we have about the use of balanced crystalloids in resuscitation in emergency room and critically ill patients," said Charles Weber MD, from the University of Wisconsin–Madison.

Previous data gave the medical community indications, but "this is more definitive, and will probably change practice," he told Medscape Medical News. "It's one of those studies that makes us shake our heads and say, 'Finally!'"

"Traditionally, we've always used saline; it's a reflex, not something you think through," Dr Weber explained. "People will have to recalibrate."

Balanced crystalloids are slightly more expensive, but in the long run, far more money will be saved by switching, he pointed out. For example, with septic patients, highlighted by researchers as a group particularly susceptible to saline, "you could keep them from going on renal replacement therapy and ultimately save some of their lives. That will definitely be cost-effective in the long run," he noted.

It is interesting how often there is a standard of practice that's been a certain way for decades, even though it has never really been proven to be the ideal therapy, he pointed out. "This is the case with normal saline."

Dr Semler, Dr Self, Dr deBoisblanc, and Dr Weber have disclosed no relevant financial relationships.

CHEST 2017: American College of Chest Physicians Annual Meeting: Session 4062. Presented October 31, 2017.

Follow Medscape on Twitter @Medscape and Ingrid Hein @ingridhein

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