The SMART Trial: LR vs NS in ICU

Will using balanced crystalloids (i.e. lactated ringers, Plasmalyte) compared to normal saline solutions result in better clinical outcomes in the ICU?

The SMART trial enrolled 15,802 patients, and half this population received normal saline and half received balanced crystalloids the duration of their ICU stay. The study looked at major adverse kidney events within 30 days as primary outcome. This outcome includes a composite of death from any cause, new renal-replacement therapy or persistent renal dysfunction.

RESULTS: In this study, 14.3% patients (balanced crystalloids) vs 15.4% patients (normal saline) had a major adverse kidney event. Odds ratio 0.91, 95% CI 0.84 to 0.99, p= 0.04.

CONCLUSION: Among critically ill adults, fluid administration with balanced crystalloids resulted in a lower rate of major adverse kidney event compared to normal saline.

CAVEAT for Neurocritical care: Relative hypotonicity of balanced crystalloids could increase ICP in patients with brain injury. In the trial, patients with brain injury were given option to use normal saline regardless of trial group randomized. This study should not be used to guide fluid administration in patients with TBI. Use clinical judgement: favor LR over NS in general, but in patients with ICP issues, evaluate on case by case basis.

Interestingly, in subgroup analysis, patients in neuro unit, there was a trend to better outcome favoring use of balanced crystalloids. Also interesting – patient in cardiac unit, trend favors the use of sodium.

Above: Chloride and bicarbonate concentrations better with balanced crystalloids (blue).

Reference:

Balanced Crystalloids versus Saline in Critically Ill Adults. (2018). Journal Club AINS, 07(03), 139-139. doi: 10.1055/a-0636-8489