Written by Alex Chen, MD
In non-critically ill patients that received IV fluids in the ED, there was a lower incidence of major adverse kidney events in the balanced crystalloid group compared to saline (4.7% vs 5.6%) with a NNT of 111. There was no difference in terms of hospital-free days between the groups.
Why does this matter?
IV fluid is one of the most common medical interventions that we provide. In the US, the most commonly used fluid is 0.9% sodium chloride which can cause hyperchloremic metabolic acidosis and may impair renal perfusion. This study hoped to shed light on the clinical effect of balanced crystalloids (which was primarily lactated Ringer's in this study) vs normal saline in non-critically ill adults in the ED.
“What’s gotten into Norm? He’s so salty right now.” –some balanced solution
This was a single-center, randomized, multiple-crossover, pragmatic trial of 13,347 patients. They included adult patients who received at least 500 ml of IV fluid and were admitted to a non-ICU bed in the hospital.
While there was no significant difference in hospital-free days (primary outcome), they did find that there was a significant difference in the secondary outcome of major adverse kidney events (MAKE) at 30 days in the balanced fluid group vs normal saline (4.7% vs 5.6%, AOR 0.82, P 0.01). MAKE was defined as, "a composite of death from any cause, new renal-replacement therapy, or persistent renal dysfunction (defined as an elevation of the creatinine level to ≥200% of baseline)." Interestingly, those most likely to benefit from balanced fluids (lower incidence of MAKE) had higher baseline chloride levels (>110 mmol/L) and Cr levels (>1.5mg/dl). This lower incidence of MAKE in the balanced fluid group is consistent with the SMART trial which looked at patients who were admitted to the ICU.
The difference in MAKE corresponds to a NNT of 111. The cost difference between NS and balanced crystalloid is minimal, and there is little downside to using the latter. While this is a small risk difference for the individual, it has implications on the larger scale. I will be utilizing balanced fluids for the majority of my patients for now.
Balanced Crystalloids versus Saline in Noncritically Ill Adults. N Engl J Med. 2018 Mar 1;378(9):819-828. doi: 10.1056/NEJMoa1711586. Epub 2018 Feb 27.