Quite the contrary, it is NS that has been proved to promote metabolic acidosis. Although theories vary, the dilutional effect on bicarbonate concentrations and an increase in unpaired anions (Cl-) resulting in a non-gap acidosis are two common explanations.¹

On March 1, 2018, Self et al published two studies from Vanderbilt on this topic, one focusing on the critically ill and the second on those not critically ill but admitted from the emergency department. Although un-blinded, the studies provide valuable insights. The first found that, “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.”⁶ Although there was no difference in the hospital-free days in the non-critically ill study, the authors found that, “balanced crystalloids resulted in a lower incidence of major adverse kidney events within 30 days than saline (4.7 percent vs. 5.6 percent; adjusted odds ratio, 0.82; 95 percent CI, 0.70 to 0.95; P=0.01).”⁷

In most cases, it may be time to check your saline at the door in favor of LR.

References

1. Severs D, Hoorn EJ, Rookmaaker MB. A critical appraisal of intravenous fluids: from the physiological basis to clinical evidence. Nephrol Dial Transplant. 2015;30(2):178-187.
2. Hahn RG, Lyons G. The half-life of infusion fluids: an educational review. Eur J Anaesthesiol. 2016;33(7):475-482.
3. Drobin D, Hahn RG. Kinetics of isotonic and hypertonic plasma volume expanders. Anesthesiology. 2002;96:1371-1380.
4. Rochwerg B, Alhazzani W, Sindi A, et al. Fluid resuscitation in sepsis: a systematic review and network meta-analysis. Ann Intern Med. 2014;161:347-355.
5. Ross SW, Christmas AB, Fischer PE, et al. Impact of common crystalloid solutions on resuscitation markers following Class I hemorrhage: a randomized control trial. J Trauma Acute Care Surg. 2015;79(5):732-740.
6. Semler MW, Self WH, Wanderer JP, et al. Balanced crystalloids versus saline in critically ill adults. N Engl J Med. 2018;378:829-839.
7. Self WH, Semler MW, Wanderer JP, et al. Balanced crystalloids versus saline in noncritically ill adults. N Engl J Med. 2018;378:819-828.