Patients in the intensive care unit frequently receive IV fluid.  For more than 100 years, two basic types of IV fluid have been available: saline (which contains more chloride than human blood) and balanced crystalloids (which contains about the same amount of chloride as human blood).  No large trials had previously evaluated which fluid resulted in the best outcomes for patients.  Among almost 16,000 patients in 5 intensive care units, the SMART trial found that using balanced crystalloids instead of saline decreased the risk of death, dialysis, or lasting kidney problems.  These findings suggest that most hospitalized patients without a specific reason for receiving saline should be treated with balanced crystalloids when an IV fluid is needed.

Background: Both balanced crystalloids and saline are used for intravenous fluid administration in critically ill adults, but it is not known which results in better clinical outcomes.

Methods: In a pragmatic, cluster-randomized, multiple-crossover trial conducted in five intensive care units at an academic center, we assigned 15,802 adults to receive saline (0.9% sodium chloride) or balanced crystalloids (lactated Ringer’s solution or Plasma-Lyte A) according to the randomization of the unit to which they were admitted. The primary outcome was a major adverse kidney event within 30 days – 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) – all censored at hospital discharge or 30 days, whichever occurred first.

Results: Among the 7942 patients in the balanced-crystalloids group, 1139 (14.3%) had a major adverse kidney event, as compared with 1211 of 7860 patients (15.4%) in the saline group (marginal odds ratio, 0.91; 95% confidence interval [CI], 0.84 to 0.99; conditional odds ratio, 0.90; 95% CI, 0.82 to 0.99; P=0.04). In-hospital mortality at 30 days was 10.3% in the balanced-crystalloids group and 11.1% in the saline group (P=0.06). The incidence of new renal-replacement therapy was 2.5% and 2.9%, respectively (P=0.08), and the incidence of persistent renal dysfunction was 6.4% and 6.6%, respectively (P=0.60).

Conclusions: Among critically ill adults, the use of balanced crystalloids for intravenous fluid administration resulted in a lower rate of the composite outcome of death from any cause, new renal-replacement therapy, or persistent renal dysfunction than the use of saline. (Funded by the Vanderbilt Institute for Clinical and Translational Research and others; SMART-MED and SMART-SURG ClinicalTrials.gov numbers, NCT02444988 and NCT02547779 .).

Manuscript Title: “Balanced Crystalloids versus Saline in Critically Ill Adults.”

Journal: New England Journal of Medicine

PMID: 29485925