Written by Aaron Lacy
There have been multiple publications since the original SMART and SALT-ED trials, including this Brazilian RCT that initially said fluid choice didn’t matter in critically ill patients. However, a secondary analysis of the BaSICS RCT suggests otherwise.
Why does this matter?
In 2018, both the SMART and SALT-ED trials raised eyebrows across the world, showing decreased major adverse kidney events when balanced crystalloids were given instead of normal saline, with a bigger difference in critically ill patients. However, two major RCTs were published after this that showed no difference in mortality or renal events. So, does this matter? Well, from a clinical standpoint we give a lot of fluid in medicine, so if one is better than another, it’s a big deal. However, for me this is important, because this article highlights why study design matters and why we really need to dig into landmark papers when they come out.
A tale of three studies
In 2021 the Brazil-based BaSICS RCT was published. This study concluded that in critically ill adults admitted to the ICU, there was no difference in 90-day mortality or major adverse kidney events when comparing patients who received either balanced (PlasmaLyte) crystalloids or normal saline. Shortly after this, in early 2022, the Australian based PLUS RCT had similar findings, showing no difference in 90-day mortality or major adverse kidney events.
Both studies seemed to contradict the major findings from SMART and SALT-ED. However, both SMART and SALT-ED had fluid choice originated in the emergency department and continued this fluid coordination in the operating room and ICUs after admission. In both the BaSICs and PLUS RCTs, patients were only enrolled after admission to the ICU. The authors of the BaSICS trial did a secondary analysis of their own population to see if there was a different conclusion when looking at patients who received fluids before enrollment in their trial.
The secondary analysis of BaSICs showed that a whopping 68% (10,520) of enrolled patients had balanced crystalloids (3,202), saline (2,096), or both (1,862) prior to enrollment. For patients that received only balanced solutions before enrollment the probability of benefit in 90-day mortality was high (0.92). They also further teased out the reason for admission, whether it was planned, unplanned, or unplanned because of sepsis. The probability of benefit rose when admission was unplanned to the ICU for sepsis (0.96) and for all planned admission (0.97).
This secondary analysis shows findings consistent with the SMART trial. It might not matter as much what fluids you choose when patients are on their third, fourth, or fifth liter of fluid – but especially for the sickest patients, it sure seems like the initial resuscitation fluid makes a difference. I will continue to resuscitate in the ED with balanced crystalloids (with few exceptions) and advise critical care transport teams and prehospital providers to do the same.
Check out this editorial on the topic which nicely summarizes the journey of balanced crystalloids versus saline in the literature.
Association between Type of Fluid Received Prior to Enrollment, Type of Admission, and the Effect of Balanced Crystalloid in Critically Ill Adults. Am J Respir Crit Care Med. 2022;205(12):1419-1428. Doi:10.1164/rccm.202111-2484OC