The study by Young et al.[1] demonstrated that use of a buffered crystalloid solution did not reduce the risk of acute kidney injury in intensive care patients, in comparison with the use of saline.

However, we think that some limitations of the study should be addressed.

First, a total of 60% of the enrolled patients underwent elective surgery, and fluid resuscitation is rarely indicated for such patients. Furthermore, only 4% of the enrolled patients had sepsis or trauma, which usually requires fluid resuscitation. Therefore, this study population is not representative of the critically ill patients who generally need fluid therapy, and the study fluid may thus be used only as a maintenance fluid and not as a resuscitation fluid.

Second, because of the above-mentioned reason, each study fluid was infused at a median volume of 1,200∼1,400 ml on day 0 and 40∼90 ml on day 1. A small amount of 0.9% saline solution will not induce hyperchloremia and metabolic acidosis, or will induce very short-term hyperchloremia [2]. The mechanism of 0.9% saline-induced renal dysfunction is that infusion of a supraphysiological concentration of chloride induces hyperchloremia, which, in turn, causes renal vasoconstriction and decreased glomerular filtration rate [3]. Therefore, the small amount of infused saline in this study may not induce hyperchloremia and renal dysfunction. However, this study did not show data about the serum chloride level or acid-base balance of the study population.

Third, because the primary outcome of this study was renal dysfunction, patients with renal dysfunction were excluded. However, a large proportion of critically ill patients usually have variable grades of renal dysfunction, and saline may cause a higher degree of hyperchloremia and may have a more harmful effect to critically ill patients in general than to the study population.

In conclusion, the use of fluid therapy in the population of this study is not representative of the situation of resuscitation or fluid therapy in general intensive care units. Randomized controlled trials are needed to compare the use of 0.9% saline and buffered fluid as a resuscitation fluid in high-risk or critically ill patients with shock before drawing a definitive conclusion.

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