Balanced Crystalloids versus Saline in Critically Ill Adults (SMART)

Normal saline (0.9% NaCl) is the most commonly used IV fluid, but its high chloride content may cause hyperchloremic metabolic acidosis and AKI. Balanced crystalloids (lactated Ringer's, PlasmaLyte) more closely mimic plasma composition.

Pragmatic cluster-crossover RCT (15,802 ICU patients) comparing balanced crystalloids vs. normal saline for all IV fluid administration in the ICU.

Balanced crystalloids reduced the composite of death, new renal replacement therapy, or persistent renal dysfunction (14.3% vs 15.4%, OR 0.90, p=0.04). Absolute risk reduction was modest but consistent.

Balanced crystalloids (lactated Ringer's or PlasmaLyte) are preferred over normal saline for most ICU patients. Normal saline should be avoided in large volumes due to hyperchloremic acidosis and AKI risk. Exception: head trauma (avoid hypotonic solutions).

Pragmatic design with cluster-crossover — contamination possible. Effect size was small. Concurrent SALT-ED trial confirmed findings in non-ICU setting.