Difference between revisions of "Hyponatremia"

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==Causes==
 
==Causes==
The cause of Hyponatremia is poorly understood, but there appear to be two likely causes in runners.  
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The cause of Hyponatremia is poorly understood, but there appear to be several likely causes in runners.  
 
# Excessive water intake can cause 'dilutional Hyponatremia'<ref name="ref1"/>. Healthy kidneys can excrete about 2 pints (1 liter) of fluid per hour, but this may be reduced by exertion or illness <ref name="ref3"/>. So drinking &gt;6 pints in 4 hours could easily exceed the kidneys capacity to cope. The recent rise in Hyponatremia may be due to earlier advice to athletes to "drink as much as possible" <ref name="ref13"/>, combined with a general concern about salt intake.
 
# Excessive water intake can cause 'dilutional Hyponatremia'<ref name="ref1"/>. Healthy kidneys can excrete about 2 pints (1 liter) of fluid per hour, but this may be reduced by exertion or illness <ref name="ref3"/>. So drinking &gt;6 pints in 4 hours could easily exceed the kidneys capacity to cope. The recent rise in Hyponatremia may be due to earlier advice to athletes to "drink as much as possible" <ref name="ref13"/>, combined with a general concern about salt intake.
# For ultrarunners, I would argue that Hyponatremia is more likely to be caused by a insufficient electrolytes combined with appropriate drinking.  
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# [[Sodium Deficiency]], combined with adequate or excessive hydration.
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# [[NSAIDs and Running|NSAID]] usage, which is been linked to hyponatremia.
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# [http://en.wikipedia.org/wiki/Syndrome_of_inappropriate_antidiuretic_hormone_hypersecretion Syndrome Of Inappropriate Antidiuretic Hormone Hypersecretion], or SIADH, is where the body secretes too much of the hormone (vasopressin) that reduces the urine output of the kidney.it's not clear if this is an independent cause of hyponatremia, or if this is a mechanism underlying one of the other causes.
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==Likelyhood==
 
==Likelyhood==
 
Hyponatremia can be common in endurance athletes:
 
Hyponatremia can be common in endurance athletes:

Revision as of 21:09, 18 November 2011

While dehydration can be dangerous, the danger from Hyponatremia is far greater. Hyponatremia is where the sodium (salt) levels in the blood becomes too dilute.

1 Symptoms

Initial symptoms tend to be a gain in weight and a general swelling and 'puffiness', most noticeable in the hands. More severe symptoms are caused by a swelling of the brain (cerebral edema) including nausea, vomiting, headache and malaise [1]. The link between Hyponatremia and Cramps is not clear, but there is evidence that increased sodium intake can alleviate the problem.

2 Causes

The cause of Hyponatremia is poorly understood, but there appear to be several likely causes in runners.

  1. Excessive water intake can cause 'dilutional Hyponatremia'[2]. Healthy kidneys can excrete about 2 pints (1 liter) of fluid per hour, but this may be reduced by exertion or illness [3]. So drinking >6 pints in 4 hours could easily exceed the kidneys capacity to cope. The recent rise in Hyponatremia may be due to earlier advice to athletes to "drink as much as possible" [4], combined with a general concern about salt intake.
  2. Sodium Deficiency, combined with adequate or excessive hydration.
  3. NSAID usage, which is been linked to hyponatremia.
  4. Syndrome Of Inappropriate Antidiuretic Hormone Hypersecretion, or SIADH, is where the body secretes too much of the hormone (vasopressin) that reduces the urine output of the kidney.it's not clear if this is an independent cause of hyponatremia, or if this is a mechanism underlying one of the other causes.

3 Likelyhood

Hyponatremia can be common in endurance athletes:

  • In a 1997 Ironman triathlon, almost 4% of competitors received attention for Hyponatremia [5].
  • In a study of the 2002 Boston Marathon, 13% of finishers had some level of Hyponatremia, and 0.6% had critical Hyponatremia [6].
  • In the Houston marathon[7], 21 runners who received medical help were suffering from Hyponatremia. Runners with Hyponatremia were generally slower and drank more.
  • However, a study[8] of the 2002 Christchurch Marathon in New Zealand, where aggressive hydration was not recommended, none of the 134 runners measured had Hyponatremia.

4 Risk Factors

The study[9] revealed that the risk factors for Hyponatremia in marathons include

  • A slow finish time (>4 hour)
  • Consumption of >6 pints (3 liters) of water during the race
  • BAA suggests a 'slight build' is also a risk factor

5 Preventing Hyponatremia

The key to preventing Hyponatremia is to ensure adequate electrolyte intake and to drink when thirsty. See Practical Hydration.

6 References

  1. Hyponatremia http://en.wikipedia.org/wiki/Hyponatremia
  2. Exercise-Associated Hyponatremia http://cjasn.asnjournals.org/cgi/content/abstract/2/1/151
  3. Water Intoxication http://en.wikipedia.org/wiki/Water_intoxication
  4. USATF Announces Major Changes in Hydration Guidelines for Long Distance Runners http://www.rrm.com/archive03/042803n2.htm
  5. Micronutrient Information Center - Sodium http://lpi.oregonstate.edu/infocenter/minerals/sodium/
  6. Hyponatremia among Runners in the Boston Marathon http://content.nejm.org/cgi/content/abstract/352/15/1550
  7. Hew TD, Chorley JN, Cianca JC, et al. The incidence, risk factors and clinical manifestations of hyponatremia in marathon runners. Clin J Sports Med. 2003;13:41–47 http://www.ncbi.nlm.nih.gov/pubmed/12544163
  8. Study of hematological and biochemical para... [Clin J Sport Med. 2004] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/15523206
  9. BAA - HYDRATION, DEHYDRATION AND HYPONATREMIA http://www.bostonmarathon.org/BostonMarathon/WelcomeBooklet.asp#hydration