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Evevident
Original paper
2018NEJMPulmonary/Critical Care

SMART

Balanced Crystalloids versus Saline in Critically Ill Adults

RCTIV fluids / ICU

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Overview

In ICU patients, balanced crystalloids modestly reduced major adverse kidney events compared with saline.

Clinical takeaway

SMART made balanced crystalloids a default resuscitation fluid in many ICUs, especially when large-volume crystalloid exposure or kidney risk is present.

Key result

Major adverse kidney events at 30 days were 14.3% with balanced crystalloids vs 15.4% with saline.

Practice impact

Supports balanced crystalloids as default ICU fluid unless a specific reason for saline exists.

Evidence

Study design

Pragmatic, single-center, cluster-randomized, multiple-crossover trial.

Enrollment

15,802

Follow-up

30 days.

Geography

United States

Clinical question

Do balanced crystalloids improve kidney-centered outcomes compared with saline in critically ill adults?

Population

  • Adults admitted to five ICUs at a single large academic medical center.

Intervention

Balanced crystalloids, primarily lactated Ringer's or Plasma-Lyte.

Comparator

0.9% saline.

Primary outcome

Major adverse kidney events within 30 days (MAKE30: death, new renal-replacement therapy, or persistent renal dysfunction).

Balanced crystalloids modestly reduced the composite of death, new dialysis, or persistent renal dysfunction compared with saline in critically ill adults.

Odds ratio / 0.91 / CI 95% CI 0.84-0.99 / p=0.04

Key results

  • MAKE30 occurred in 14.3% with balanced crystalloids vs 15.4% with saline; OR 0.91 (95% CI 0.84-0.99; p=0.04).
  • The absolute effect was modest (~1 percentage point) but affects large numbers of ICU patients.
  • The benefit appeared more pronounced in the sepsis subgroup.

Harms

  • Balanced crystalloids did not increase adverse events; feared hyperkalemia with lactated Ringer's was not observed.
  • Saline was associated with more hyperchloremia and metabolic acidosis.

Clinical Use

When to cite

  • When choosing resuscitation fluids for ICU patients and explaining why balanced crystalloids may be favored over saline.

Practice impact

  • Supports balanced crystalloids as default ICU fluid unless a specific reason for saline exists.

Applicability

  • Most applicable to critically ill adults receiving moderate-to-large volumes of crystalloid in the ICU.

Limitations

  • Single-center pragmatic cluster-crossover design with open-label fluid assignment.
  • Modest absolute effect size on a composite outcome.
  • Cannot isolate which component of the composite drove the benefit.

Common misinterpretations

  • The benefit is a small composite-outcome shift, not a large mortality reduction.
  • Concerns that lactated Ringer's causes clinically important hyperkalemia were not supported.

Citation

Semler MW, Self WH, Wanderer JP, et al. Balanced Crystalloids versus Saline in Critically Ill Adults. N Engl J Med. 2018;378(9):829-839. doi:10.1056/NEJMoa1711584

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.