Saturday, September 14, 2019

Normal Saline: A History Lesson for the Inappropriate Name

A little history lesson, my friends, regarding the origins of us calling 0.9% saline solution, aka 0.9% sodium chloride, "normal saline".
We are all disappointed in ourselves. You've been calling it normal saline, I've been calling it normal saline, we just can't stop ourselves! Of course you know I am referring to 0.9% sodium chloride solution used so commonly, and many times inappropriately, in our everyday practice. Why is it not normal? Well, I have covered this many times on my Instagram page and YouTube videos. First of all, the sodium concentration in serum is 140meq/L. The reference range in the labs are usually 135-145meq/L. What's the sodium concentration in "Normal Saline"? 154meq/L. How much chloride is in serum? 98-109meq/L. What about in "normal saline"? 154meq/L because it's equal parts sodium and chloride. We can continue talking about strong ion difference and all the adverse effects of the 0.9% saline but that will take me forever. It's Saturday and I have a birthday party to go to. Where in the world did the associate with "normal" come from? The inspiration for this post came from @anursingnote and her discussion with @med.life.crisis, two RN's who are trying to kick butt and get smarter every day. You go girl(s)!
This article is not free, unfortunately, but they do make a couple key points, all of which show that even though they used the word "normal", it's not in the appropriate way. You're never going to think about a Hamburger now without thinking about 0.9% saline solution. Sorry I ruined that for you.
Here's how all this went down in chronological order:
I credit the authors of this paper for doing much of this heavy lifting, by the way. I can't actually get my hands on many of these papers. I'm going to do my best to briefly summarize.
1888: Hamburger. This Dutch physiologic chemist performed in vitro studies (not in vivo, take a second to let that process) where he found that there was less hemolysis with 0.92% saline than other concentrations.
1888: Dr Churton. "he was ordered transfusion of ‘normal saline’ solution in order to replace the fluid thus lost". That fluid was nothing like the saline we know and are still trying to understand to this day. That particular fluid had 150meq/L of Na and 128meq/L of chloride. It also had some bicarb in it.
1892: Dr Spencer used the term "normal salt solution" but the composition of the fluid was not defined.
There are plenty more goodies in the article which I recommend you try to get your hands on. The article is going to definitely be included in my lecture regarding intravenous fluids that I will be giving to the anesthesia department in my shop next month and on various lectures I have scheduled nationally next year. It's that important. A great job by the authors!
All in all, can we really stop saying "normal saline"? I think it's too embedded in our vernacular and it'll be too challenging to fix. I am always trying to make a conscious effort to stop but it's challenging because I have been hearing it for over a decade now. I'm getting old.
-EJ





Link to Abstract


Citation:
Awad S, Allison SP, Lobo DN. The history of 0.9% saline. Clin Nutr Edinb Scotl. 2008;27:179–188.

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