Difference between revisions of "Hyponatremia"
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==Causes== | ==Causes== | ||
| − | The cause of Hyponatremia is poorly understood, but | + | The cause of Hyponatremia is poorly understood, but there appear to be two 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 >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. | ||
| + | ==Likelyhood== | ||
| + | Hyponatremia can be common in endurance athletes: | ||
* In a 1997 Ironman triathlon, almost 4% of competitors received attention for Hyponatremia <ref name="ref4"/>. | * In a 1997 Ironman triathlon, almost 4% of competitors received attention for Hyponatremia <ref name="ref4"/>. | ||
* In a study of the 2002 Boston Marathon, 13% of finishers had some level of Hyponatremia, and 0.6% had critical Hyponatremia <ref name="ref2"/>. | * In a study of the 2002 Boston Marathon, 13% of finishers had some level of Hyponatremia, and 0.6% had critical Hyponatremia <ref name="ref2"/>. | ||
==Risk Factors== | ==Risk Factors== | ||
| − | The study revealed that the risk factors for Hyponatremia include | + | The study<ref name="ref12"/> revealed that the risk factors for Hyponatremia in marathons include |
* A slow finish time (>4 hour) | * A slow finish time (>4 hour) | ||
* Consumption of >6 pints (3 liters) of water during the race | * Consumption of >6 pints (3 liters) of water during the race | ||
| − | * BAA suggests a 'slight build' is also a risk factor | + | * BAA suggests a 'slight build' is also a risk factor |
| + | ==Preventing Hyponatremia== | ||
| + | The key to preventing Hyponatremia is to ensure adequate electrolyte intake and to drink when thirsty. See [[Practical Hydration]]. | ||
| − | |||
== References == | == References == | ||
<references> | <references> | ||
Revision as of 14:08, 24 April 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 two likely causes in runners.
- 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.
- For ultrarunners, I would argue that Hyponatremia is more likely to be caused by a insufficient electrolytes combined with appropriate drinking.
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].
4 Risk Factors
The study[7] 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
- ↑ Hyponatremia http://en.wikipedia.org/wiki/Hyponatremia
- ↑ Exercise-Associated Hyponatremia http://cjasn.asnjournals.org/cgi/content/abstract/2/1/151
- ↑ Water Intoxication http://en.wikipedia.org/wiki/Water_intoxication
- ↑ USATF Announces Major Changes in Hydration Guidelines for Long Distance Runners http://www.rrm.com/archive03/042803n2.htm
- ↑ Micronutrient Information Center - Sodium http://lpi.oregonstate.edu/infocenter/minerals/sodium/
- ↑ Hyponatremia among Runners in the Boston Marathon http://content.nejm.org/cgi/content/abstract/352/15/1550
- ↑ BAA - HYDRATION, DEHYDRATION AND HYPONATREMIA http://www.bostonmarathon.org/BostonMarathon/WelcomeBooklet.asp#hydration
