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Flipside: A Dissenting Opinion on RL and NS

January 12, 2013

As mentioned in my previous posts on Peer-review in FOAM (here and here), following my post on Ringer’s Lactate and Normal Saline I received feedback via e-mail in an e-mail from Dr. Rory Spiegel, an EM resident from Newark, NJ. He offered a well thought out dissenting opinion that I felt deserved a post of its own to counterbalance my previous one.

Here is what he had to say (greetings/goodbyes removed for length):

On the topic of your latest post I have to say I respectfully disagree. I’ve read Dr. Weingart’s posts on this topic as well, and as much respect I have for him, I think on this topic he is mistaken. Well that may be overstating the fact. There may in fact be a small physiological difference but whether that translates into a clinical difference has never been determined. For years now people having been trying to show the superiority of a multitude of fluids over normal saline for countless disease states and as far as I am aware no one has ever done so. Sure when they do preliminary non-randomized trials looking at surrogate endpoints they look better, but whenever you compare them in a random trial it turns out to be equivalent and in some cases, like hydroxyethyl starch, even trend to worse outcomes.

The evidence put forth by Dr. Weingart is not much proof in either direction. There are countless examples of interventions that look great until you do a placebo controlled trial.  In these kind of studies you are never able to account for all the variables. The sicker patients could have needed more blood transfusions which means they were less likely to get LR and more likely to get NS. Even still if you look at the outcomes that actually matter, there was no difference in mortality, ICU length of stay, or need for prolonged RRT.
There is a lack of good evidence overall, otherwise we wouldn’t be having this discussion. I just think it is curious when people who use NS as their preferred fluid of choice get accused of not knowing any better.  I’ve read everything I can find on the topic and I have yet to find any data that shows that LR is superior to NS in any way other than it theoretical reasoning.
In my response I noted some of my motivations for siding with RL. I think RL just makes physiologic sense. This has been backed up with studies which show that, relative to NS, it causes less metabolic derangements in ED patients. Healthy volunteers also seem to like it as they pee earlier and more often and don’t retain as much fluid. Some might also claim that these findings have a viable mechanism to explain them based on kidney physiology and chloride loading in denervated greyhound kidneys…I don’t make that claim, but its interesting to point out a potential mechanism.
Also, I do think that the recent renal findings with lower chloride fluids in ICU patients is relevant, even if it is a surrogate marker, because dialysis sucks for patients and is very expensive for our respective health care systems.
I very much appreciate his note that it should not be assumed that people using NS simply do not know any better. Like Dr. Spiegel, many of them may be very up-to-date on their literature but remain unconvinced of the glories of RL. And they could still be proven right. In his response, he said:
I’ve read both those studies you sent and yes I agree they both found small trends towards the LR in the outcomes they measured. But these are the kind of studies that I initially wrote in protest of. When you look at these surrogate end points there appears to be trends towards benefits, but what we really care about is if LR actually affects patient oriented outcomes. If you go back and look at the early studies on albumin and Hydroxyethyl Starch they looked just like this. As long as you look at surrogate end points they all do better then NS but when you look at the SAFE trial or the large trial recently published in the NEJM these differences don’t translate into mortality or morbidity benefits (and in the later case trends towards increased harm).

Now you could very well argue, why not just use LR for everything since there is no proof that NS is superior and I could not very well disagree with you. The way I look at it is what we do is extremely difficult and we make thousands of decisions each day. So if there is no actual benefit to remembering all the multitudes of fluid choices and the multitudes of situations they may be theoretically beneficial why fill much needed space with seemingly needless stoichiometry.
Now because this is going to be posted and I am feeling quite small when I see the likes of Scott Weingart (one of my EM heroes) posting an assenting opinion I feel it’s only fair I mention that I am not alone in dissenting opinion. The Godfather of emergency medicine, Jerry Hoffman, has proclaimed on countless occasions on EMA that NS is the fluid to give in every situation. If you are in a hypotonic state it is hypertonic in relation. If you are in a hypertonic state it is hypotonic in relation.
Anyway I feel better now that I have someone smarter and far more experienced than myself standing (at least in proxy) on my side of this debate.
Thanks for letting me take part in this discussion. Physiologic reasoning has led us down many blind paths and dark allies. It is only when we use the light of critical research we discover which are dead ends and which lead us and our patients to a better place. It is blogs like yours that will help promote taking such critical looks, so thank you.
Some very good points that deserve consideration. In the end, I am still going to use RL as my go-to fluid for three reasons: 1 – as granted by Dr. Spiegel, there is no evidence that it is better than RL, 2 – I think the “soft”evidence trends in its favor, 3 – it is insignificantly more expensive (see my previous post on the topic – bottom line it’s ~$0.20/L extra).
However, I recognize the wisdom of Dr. Weingart, who made the comment that:

“it just seems like good medicine to treat fluids like any other drug and actually choose the ideal one for the clinical situation.”

And discussed this in depth in his podcast “Choose the Solution Based on the Problem”
In conclusion, having a Coke every once in awhile can be nice! In fact, in many cases it may just be the thing you need to make the perfect drink. Other times it’s going to be Pepsi (D5NS – the same as Coke, only sweeter), Diet Coke (1/2NS) or Diet Pepsi (D51/2NS). There’s certainly a role for all of these fluids. Shoutout to @socmobem and @ETtube for coming up with the rest of the pop equivalents!!

Thanks again to Dr. Spiegel for making me think, supplying the majority of the content of this post and acting as a peer-reviewer for my FOAM. This will most definitely be the last that I write on the topic of fluids for a lonnnng while! Stay tuned for more boring with upcoming posts on otitis media and a follow-up on constipation. I will also continue to expand the mentorship section with a post on preparing for EM residency interviews.

As always, let me know what you think in the comments section below! If you enjoyed this discussion there will be more to come and I’d greatly appreciate it if you followed my RSS feed (see top right corner), signed up for e-mail notifications of new posts (right column), or gave me a RT or follow on twitter!

Brent Thoma @boringem


From → Medical

One Comment
  1. jacinta permalink

    i enjoyed that discussion

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