Is Normal Saline Bad for the Kidneys?
From Skeptical Scalpel
This week, the two heavyweight medical journals, JAMA and the New England Journal of Medicine, featured papers describing the effect of certain intravenous fluids on the incidence of renal failure in critically ill ICU patients.
The JAMA paper compared normal saline (relative to human plasma, a high chloride-containing solution) administration to more physiologic, low chloride-containing IV fluids such as Hartmann’s solution (very similar to Ringer’s lactate) or Plasma-Lyte 148. It showed that using the low chloride intravenous infusions led to a statistically significant decrease in the incidence of acute kidney injury and the need for renal replacement therapy.
The NEJM paper compared the use of intravenous hydroxyethyl starch (HES) fluid resuscitation to normal saline and found that patients given HES had significantly more acute kidney injury and needed more renal replacement therapy. Bear in mind that HES is actually a solution of 6% HES in normal saline.
Neither study found a significant difference in mortality rates related to the various solutions used.
Both studies were performed in Australia during different time periods. The JAMA paper was based on research from a single hospital in Melbourne in 2008-2009 and was a before-and-after trial while the NEJM study was multi-institutional, randomized and prospective and took place from December 2009 to January 2012.
Is normal saline bad for the kidneys? Yes. If you compare high chloride normal saline to lower chloride solutions, normal saline causes more renal dysfunction and need for renal replacement therapy. Normal saline vs. HES really compared normal saline alone to 6% starch in normal saline, and showed that the starch is probably the factor causing renal injury.
So what is a clinician to do? Normal saline is not really “normal.” Solutions containing amounts of chloride closer to that of human plasma are the correct ones to use. As we surgeons have maintained all along, Ringer’s lactate should be the resuscitation fluid of choice in the U.S.
See the table below for the amounts of sodium, chloride and buffer in standard IV solutions.