Exercise Induced Hyponatremia

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Exercise Induced Hyponatremia
Jessica Dare Evans, MSN, CEN, ARNP, NP-C

With the changing of the seasons and cooling of the weather more and more marathon, triathlon, and ultra-distance races are being participated in. These strenuous endurance races can lead to exercised induced-hyponatremia. Severe hyponatremia can be life threatening posing the risks of permanent disability, end organ failure, and even death. Advanced Practice Clinicians (APCs) serve as the front line in recognizing an individual with severe hyponatremia and treating appropriately and efficiently. Let’s race through the causes, diagnostics, and treatment plan for exercised induced-hyponatremia with a few water stops along the way.
According to the 2015 Third International Exercise-Associated Hyponatremia Consensus Development Conference, exercise induced-hyponatremia occurs during the strenuous endurance activity or up to 24 hours after with a serum sodium level below the normal reference range of the laboratory (for the purposes of this commentary we will use the general range of 135-145 me/L). Individuals with hyponatremia can exhibit mild to severe headaches, lethargy, nausea, vomiting, weakness, dizziness, seizures, pulmonary edema, cerebral edema, and death.
A major contributing factor to this reversible disease process is the high intake of water during these races. All athletes are advised to stay well hydrated during any physical activity. Most runners will continue to drink an excessive amount of water during their entire race. This can lead to fluid overload and even hemodilution. Thirsty yet?
Let’s take a quick review of the pathology leading to hyponatremia. Anti-diuretic hormone (ADH) is the hormone that is secreted during exercise signaling the kidney to reabsorb water. ADH is also secreted when the hypothalamus detects low water content in the body from excessive sweating. Have you ever seen those runners at the end of a race who have salt crystals all stuck to them? Individuals can lose sodium through excessive sweating. The loss of salt can lead to a hypovolemic state stimulating the release of ADH. ADH is definitely holding you back from winning this race.
Diagnostics? You must obtain a serum sodium value of course, including an entire chemistry panel. And yes, look for other diagnoses such as rhabdo with your CPK, EKG, chest xray, ct brain if deemed appropriate.
Treatment? It is recommended for mild to moderate symptoms such as headache, dizziness, nausea and vomiting as well as documented hyponatremia to be treated with a very minimum fluid restriction. Once the patient has witnessed urine output, symptoms will resolve correcting itself. The Hyponatremia Consensus Conference 2015 also recommends for those patients who fail to suppress ADH an oral or intravenous bolus of hypertonic saline may be beneficial.
For patients who are shown to have severe symptoms of hyponatremia such as seizures, confusion or coma should be treated with 100ml of 3 percent hypertonic saline. It is found to show a significant increase of serum sodium concentration by 2 to 3 mEq/L. The Hyponatremia Consensus Conference 2015 also recommends that the 3 percent hypertonic saline can be administered up to one or two more times in 10 minute interval if there is no improvement in neurological symptoms after the first bolus. Once the symptoms have resolved the hypertonic saline is then discontinued.
Now that we have made it to the end of the race, let’s summarize a few key points. Any patient presenting from a high-endurance activity must be assessed for signs and symptoms of exercised-induced hyponatremia. Signs and symptoms can range from very minimal to very severe. Don’t be afraid of hypertonic saline, in these individuals it is your best friend.
Education is crucial in preventing exercised-induced hyponatremia. Mayo Clinic 2016 has outlined five critical points when educating your patient.
1. Treat associated conditions such as ADH insufficiency.
2. Be aware of signs and symptoms of hyponatremia.
3. During high endurance physical activity only drink as much fluid as you lose and use thirst as a guide.
4. Consider drinking sports beverages that contain electrolytes.
5. Most important, drink in moderation.

References

http://www.mayoclinic.org/diseases-conditions/hyponatremia/basics/prevention/con-20031445
http://www.uptodate.com/contents/exercise-associated-hyponatremia
http://journals.lww.com/cjsportsmed/Fulltext/2015/07000/Statement_of_the_Third_International.2.aspx

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