Hemodynamic instability is rewarded with a sojourn in the intensive care unit (ICU). When the intensivist sees it, they're going to throw fluids at it. Most likely a crystalloid of some type. This has been true for decades, centuries even. When I was a medical student, which was decades but not centuries ago, I used crystalloids every day on the surgical wards, in the operating room, in the emergency department, or on the medicine wards. Medicine docs preferred normal saline (NS) and surgeons used lactated Ringer's (LR). I never gave this a second thought.
During medical school, I was drawn to internal medicine by the heavy emphasis on evidence-based medicine in the field. Prior to 2015 though, there wasn't much data to support using one crystalloid formulation over another. Pre-2010, we had an American Thoracic Society (ATS) consensus statement on using crystalloid vs colloid, making recommendations largely drawn from the SAFE trial. The ATS statement also suggested starches may be harmful, a view that was confirmed in a series of articles published in 2012 and 2013. There was less discussion about what type of crystalloid was best.
In 2014, I finally read a paper that compared crystalloid formulationsIt was a network meta-analysis, which is "statistician speak" for combining disparate trials to make indirect comparisons. In the absence of large, randomized trials, this approach was a welcome addition to the data we had at the time. The authors concluded that "balanced" (typically LR or Plasma-Lyte) are superior to "unbalanced" (another term for NS) crystalloids. Balanced fluids typically have acetate or lactate and have a higher pH and lower chloride than NS. I found the signal for balanced fluids interesting at the time but promptly forgot about it.
