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VIDEO: Balanced crystalloids protect kidney better than saline

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Fluid switch has big impact for small cost
Dr. Bennett P. deBoisblanc, professor of medicine at Louisiana State University Health and director of Critical Care Services at the Medical Center of Louisiana in New Orleans. Mitchel L. Zoler/Frontline Medical News

Dr. Bennett P. deBoisblanc

The SMART and SALT-ED trials were awesome and beautifully planned. The researchers used a pragmatic design that is the wave of the future. The incremental benefit from balanced crystalloid fluids was small, about 1%, but it’s a cheap solution. If you administer 7 L of fluid to a patient the incremental cost compared with 0.9% saline is about $45. Based on the number needed to treat that the studies found, this means it would cost less than $5,000 extra to prevent one major adverse kidney event. Nothing else in the ICU or ED compares with that. It’s a phenomenal impact from a low-tech intervention.

Bennett P. deBoisblanc, MD , is professor of medicine at Louisiana State University Health and director of Critical Care Services at the Medical Center of Louisiana in New Orleans. He had no disclosures. He made these comments from the floor during discussion of the two reports.



– Treatment with balanced crystalloid IV fluids cut adverse renal events modestly but with statistical significance, compared with 0.9% saline in hospitalized patients in a pair of single-center randomized trials with more than 29,000 total patients.

Despite showing a number needed to treat with balanced crystalloids of roughly 100 to prevent one major renal event, compared with saline, the scope of IV fluid use makes even this relatively small improvement potentially important to tens of thousands of patients annually.

“It’s a small but clinically important difference,” Wesley H. Self, MD, said at the CHEST annual meeting.

“These fluids are used every day and in millions of patients annually in the United States and worldwide. There is no functional cost difference between them, and now we have the data to show that [balanced crystalloid fluids] produce a better patient outcome. It’s reasonable to consider changing practice,” based on the results, said Matthew W. Semler, MD, a pulmonologist at Vanderbilt University Medical Center in Nashville, Tenn., who led one of the two trials.

At Vanderbilt, where the two studies ran, “we’ve changed our practice and are transitioning from primarily using saline to primarily balanced crystalloid,” Dr. Semler said in a video interview. The main limitation to changing practice now because of the results is that the two trials both ran at a single center.

The findings Dr. Semler reported came from the Isotonic Solutions and Major Adverse Renal Events Trial (SMART), which randomized 7,860 ICU patients to treatment with 0.9% saline fluid and 7,942 ICU patients to treatment with balanced crystalloid fluid, either lactated Ringer’s or Plasma-Lyte A. The study’s primary endpoint was the combined 30-day rate of in-hospital death, incident need for renal replacement therapy, or at least a doubling of the patient’s baseline creatinine level, a marker of persistent renal dysfunction.

This outcome occurred in 14.3% of patients on balanced crystalloid fluid and 15.4% on saline, a 1.1% statistically significant absolute difference. The endpoint components showed that patients treated with balanced crystalloid had 0.8% less in-hospital death and 0.4% less incident renal replacement therapy; both of these between-group differences were close to having statistical significance. The two treatment groups showed less difference in the rate of persistent renal dysfunction.

The second trial had an identical design but ran instead in the emergency department. The Saline Against Lactated Ringers or Plasmalyte in the Emergency Department (SALT-ED) trial randomized 6,708 to receive balanced crystalloid and 6,639 to receive saline. The combined primary renal endpoint was 0.9% less frequent with balanced crystalloid fluid, a statistically significant difference, Dr. Self, an emergency medicine physician at Vanderbilt, reported at the meeting. In this study the between-group differences for both incident renal replacement therapy and persistent renal dysfunction were statistically significant in favor of balanced crystalloid, but the between-group mortality difference was not significantly different.

The reason why balanced crystalloid fluid produced better renal outcomes than saline remains unclear. Both Dr. Semler and Dr. Self noted that the two balanced crystalloid fluids used in the study have chloride levels that closely match normal plasma levels, but the chloride concentration in 0.9% saline is about 50% higher than plasma. Some researchers have hypothesized, based on animal findings, that this difference may influence inflammation, blood pressure, acute kidney injury, and renal vasoconstriction.

The SMART and SALT-ED trials received no commercial funding. Dr. Semler had no disclosures. Dr. Self has been a consultant to Abbott Point of Care, BioTest, Cempra, Ferring, Gilead, and Pfizer.

On Twitter @mitchelzoler

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