… only in recent years has normal saline been under the spotlight with several studies questioning whether this is the best solution to use.
Intravenous fluids are ubiquitously given to hospitalized patients, both critically and non-critically ill. The most widely used intravenous fluid remains 0.9% sodium chloride (normal saline). Although both balanced crystalloids and saline have been available for clinical use and scientific scrutiny for more than 100 years, only in recent years has normal saline been under the spotlight with several studies questioning whether this is the best solution to use.
Animal studies have shown unfavorable effects of normal saline by demonstrating that it causes acidosis because of a supranormal chloride concentration leading to detrimental vasodilation in the critically ill. This acidosis also leads to an increase in inflammation. In isolated dog kidneys and septic rats infused with saline, renal vasoconstriction was noticed, which was attributed to increased tubular chloride reabsorption. Furthermore, in healthy human volunteers, studies have demonstrated that intravenous normal saline administration leads to reduced kidney blood flow and decreased cortical tissue perfusion (1–3).
The alternative—i.e., balanced crystalloids (with a composition resembling plasma in both chloride and sodium concentrations)—may prevent the decrease in cortical perfusion and alleviate the increase in tubuloglomerular feedback because of their lower chloride content. So, what is the evidence?
Chowdhury AH, et al. A randomized, controlled, double-blind crossover study on the effects of 2-L infusions of 0.9% saline and Plasma-Lyte 148® on renal blood flow velocity and renal cortical tissue perfusion in healthy volunteers. Ann Surg 2012; 256:18–24. doi: 10.1097/SLA.0b013e318256be72
Hammond NE, et al. Balanced crystalloids versus saline in critically ill adults—a systematic review with meta-analysis. NEJM Evid 2022; 1:1–12. https://evidence.nejm.org/doi/10.1056/EVIDoa2100010