BACKGROUND AND PURPOSE:

• Historically, 0.9% sodium chloride (saline) has been the most widely used IV solution
  • Some data to suggest association with hyperchloremic metabolic acidosis, acute kidney injury and death
• Alternative is a balanced crystalloid solution, such as lactated Ringer’s solution
  • Closer electrolyte composition to plasma
  • Data suggests less acute kidney impairment and death but literature is inconsistent
• Semler et al. (N Eng J Med 2018) sought to determine which intravenous fluid administration, balanced crystalloids or saline, results in better clinical outcomes in the ICU setting

METHODS:

• Pragmatic, cluster-randomized, multiple-crossover trial of patients in the ICU
  • Adverse Renal Events Trial (SMART), which compared the use of balanced crystalloids with the use of saline in patients in medical (SMART-MED) and nonmedical (SMART-SURG) intensive care units (ICUs)
• Participants: ≥18 years of age, admitted to participating ICU
• Patients received either:
  • Balanced crystalloids (lactated Ringer’s solution or Plasma-Lyte A)
  • Saline
• The primary outcome
  • Proportion of patients who met one or more criteria for a major adverse kidney event within 30 days
    • Composite of all-cause mortality, new renal-replacement therapy, or persistent renal dysfunction
  • Secondary outcomes
    • Death before ICU discharge or at 30 days or 60 days | ICU-free days | ventilator-free days | vasopressor-free days | days alive and free of renal-replacement therapy during the 28 days after enrollment
    • Renal specific: New receipt of renal-replacement therapy | persistent renal dysfunction | acute kidney injury of stage 2 or higher | highest creatinine level during the hospital stay | change from baseline to the highest creatinine level | final creatinine level before hospital discharge

RESULTS:

• 15,802 ICU patients were enrolled
  • 7,924 patients were in balanced crystalloids group and 7860 patients were in the saline group
  • Median age 58 years
  • 42.4% were women
  • Median volume of balanced crystalloids was 1000 ml and 1020 in the saline group
• Primary outcome for adverse kidney events was higher in saline group (P=0.04)
  • balanced crystalloids (14.3%) compared to saline (15.4%)
  • Secondary outcomes
    • In-hospital mortality, incidence of new renal-replacement therapy and persistent renal function did not differ significantly between groups, nor did other secondary outcomes

CONCLUSION:

• Among critically ill adults, balanced crystalloids for intravenous fluid administration reduced the rate of composite adverse outcome that included all-cause mortality, new renal-replacement therapy, or persistent renal dysfunction
• Saline has higher chloride content that may be responsible for kidney injury
• While the primary care difference was only a 1.1% difference, over treatment of millions admitted to ICUs, the difference becomes substantial
• Clinical context is important and therefore clinicians had the option of using only saline when treating brain injury as balanced crystalloids may be too hypotonic
• The authors acknowledge that the use of composite outcomes introduces confounding variables and additional studies are needed

Learn More – Primary Sources:

Balanced Crystalloids versus Saline in Critically Ill Adults

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