Exercise Induced Hyponatremia

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Nurses Edition Commentary

Mizuho Spangler, DO, Lisa Chavez, RN, and Kathy Garvin, RN

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Lucas M. -

I don't think you guys mentioned Oral Rehydration Salts (ORS) during the podcast, thoughts? Also, there was mention of onsite field testing of Sodium; are there any recommended field test devices for this that anyone could share thoughts on?

John A. -

Regarding Oral Rehydration Salts, most of these are actually hypotonic (Na 75-90 mEq/L on the WHO formula) and thus may worsen EAH. While there are some commercially available ORS with higher sodium, my recommendation is to use a concentrated oral solution made with bullion cubes as described in the episode. For field testing sodium, I have used the Abbott model with good success, and I should note that I do not receive any support/compensation/interest, financial or otherwise, from them or any other medical company.

Adam -

In settings where field measurement of sodium is unavailable, the 2015 Consensus statement recommends empiric treatment with hypertonic saline if EAH is suspected as the cause for severe CNS symptoms. However, they also list hypernatremia as a possible cause of CNS symptoms in endurance athletes. Is there any science on differentiating the two conditions without a measured sodium value? Where I practice (wilderness) I would be unlikely to administer 3% to an ill athlete, as the symptoms overlap considerably and hypernatremia is probably more common. Administration of 3% seems risky if hypernatremia is the true condition.

John A. -

Great question. You are correct in referencing the most recent recommendation from the EAH Consensus Development conference in 2015. In my interpretation of the available data, I agree with the recommendation based on current incidence. 30-40 years ago hypernatremia was more common as athletes were told NOT to drink during exercise, resulting in a free water depleted state and hypernatremia. The pendulum then swung too far the other way and athletes (hikers, wilderness enthusiasts, etc.) were over hydrating resulting in more free water overload and hyponatremia. While there is data suggesting hypernatremia does still occur in endurance sports, the majority of data points to a much higher incidence of hyponatremia in SYMPTOMATIC patients (mild or severe), especially in those that clinically appear volume overloaded. If possible a careful history involving assessment of hydration strategy and exam can help determine if a patient has been over drinking. If not possible, i.e. obtunded patient, then again considering which patients actually develop symptoms I would support the guidelines and give hypertonic.

Venk Bellamkonda -

I am struggling with the issue of hypertonic saline here. I have no concerns about giving it to a patient with severe symptoms (athlete or "granny", slow or chronic). If the symptoms are mild however, and in the case of an athlete with normal renal function, what is the need to give a potentially dangerous medication? What if there is a misdiagnosis, medication error, underlying other condition contributing? I am struggling to see that the risk benefit ratio is in favor of giving hypertonic saline to the endurance athlete for minor symptoms. Can you help me get to where you all are when you advocate for its use here?

John A. -

I understand your concern. If you are worried about hyponatremia in a patient there are essentially three treatment strategies--fluid restriction, oral hypertonic and IV hypertonic. In any patient who will tolerate the oral HTS or fluid restriction and is not in imminent danger of herniating, this is where I start. It is safe and effective. In patients who will not tolerate these strategies is where you have to make the tough decision. Obviously this is why I advocate for providers to have on-site sodium testing available at big or high risk events, and as you state there could be other things going on (misdiagnosis, med error, underlying condition). I should clarify your question on "mild" symptoms. If an athlete is a little nauseated or weak, I would agree and not empirically give IV HTS, unless you have onsite testing. But if they have neurologic symptoms (but not necessarily seizure), no timely access to definitive care, and you have good reason to suspect EAH then I would strongly consider giving IV HTS in patients that would not tolerate the other methods of treatment. Looking at the incidence of EAH and the limited safety data of this approach, I feel (and in accordance with multiple consensus guidelines) that this is appropriate.

Amy O. -

I was just at the Hawaii Ironman World Championships last weekend as a spectator. About mile 23 of the marathon I came across a young German runner who was staggering like a drunk sailor. He had no complaints of nause or cramping...he just said he felt a little bit "out of it." It was clear that he wasn't going to finish the race and I sat with him while his coach frantically searched for medical aid. His coach was trying to force him to drink water and then gatorade and then salt tabs. When aid arrived he was not hyperthermic and I believe his blood sugar was normal. His pulse wasn't abnormally high. Once we pulled him off the course and made him sit/lay down he muscles were twitching and he seemed to get worse.

So I was torn on how to manage him right then and there without the med tent and immediate access to Na testing. Was he hyponatremic, heat exhausted, dehydrated, or (more likely) some combination of the above? I had just listened to this segment and wasn't really certain. Should we have pushed fluids on him like the coach was pushing for (he literally only took a few sips)? Should we have just waited and done nothing (which feels so odd when you are an ED doc and want to help)? Thoughts on this one...

John A. -

Great question Amy, and great to hear that you thought of the podcast in real time. You are right to consider some combination of EAH, heat illness, etc. I would have a few questions for the runner and look for a few exam findings before treating. What was his hydration strategy in the race, i.e had he been pushing fluids all day or had nothing in the last few hours? Did have have any edema or other findings to suggest a volume up status? If he had been drinking aggressively throughout the race then I would NOT push water or gatorade on him. He is likely hyponatremic and doing this will make him worse. The fact that his coach was reflexively making him drink water is a good example of the public (mis)perception that is still pervasive about hydration in endurance sports. There is actually a recent publication by Marty Hoffman looking at the current prevalence of inappropriate hydration advice on the internet https://www.ncbi.nlm.nih.gov/pubmed/27548748
Back to your question, if he was drinking aggressively then you could either give him an oral hypertonic solution as described in the segment or fluid restrict him until he urinates freely (sort of "wait and do nothing"). If you were unable to determine his hydration/volume status then I think a wait and see approach (as long as he is still clinically well appearing) or getting him to medical aid where Na can be checked is appropriate. I would NOT empirically push water and gatorade. As a side note, heat exhaustion and heat related illness (syncope, heat exhaustion, heat stroke) is a spectrum and in mild forms, rest and shade is often all that is needed for a return to baseline. Perhaps we will do a podcast on heat illness...

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