Crystalloids (i.e., 0.9% saline and lactated ringers) have been used during resuscitation for more than a century. Their invention, however, was more accidental than intentional.
Crystalloids were first used during the European Cholera epidemic of 1831. Hartog Hamburger later modified this solution in 1896 to the solution we know today as "normal" saline. Hamburger's solution was only intended for in vitro study of RBC lysis and was never intended for clinical use.
Around this time, Sydney Ringer was testing several fluids to use for physiologic studies. Ringer's lab assistant was erroneously substituting tap water for distilled water when preparing these solutions. Ringer later discovered that this tap water contained minerals making the solution "physiologic", isotonic, and safe for human use; Alexis Hartmann later added sodium lactate to create Ringer's Lactate.
Since the invention of crystalloids, many types of resuscitation fluids have been created and studied (i.e., albumins, gelatins, and starches); all have been shown to be more expensive, with no more benefit, and with possibly more harm when compared to crystalloids.
The "perfect" resuscitation fluid still alludes us today, but of all of the solutions marketed crystalloids are arguably the best...despite their accidental history.
References
Awad, S. et al. The history of 0.9% saline. Clinical Nutrition 2008 Apr;27(2):179-88.
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