Difference between revisions of "Hyponatremia"

From Fellrnr.com, Running tips
Jump to: navigation, search
User:Fellrnr (User talk:Fellrnr | contribs)
m (Symptoms)
User:Fellrnr (User talk:Fellrnr | contribs)
Line 4: Line 4:
  
 
==Causes==
 
==Causes==
The cause of Hyponatremia is poorly understood, but commonly believed to be related to excessive water intake <ref name="ref1"/>. However, I would argue that Hyponatremia is caused excessive fluid intake in the absence of sufficient electrolytes. Hyponatremia can be common in endurance athletes:
+
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 &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.  
 +
==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 (&gt;4 hour)  
 
* A slow finish time (&gt;4 hour)  
 
* Consumption of &gt;6 pints (3 liters) of water during the race
 
* Consumption of &gt;6 pints (3 liters) of water during the race
* BAA suggests a 'slight build' is also a risk factor<ref name="ref12"/>.  
+
* 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]].
  
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.
 
 
== References ==
 
== References ==
 
<references>
 
<references>

Revision as of 15:08, 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.

  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. 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

  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. BAA - HYDRATION, DEHYDRATION AND HYPONATREMIA http://www.bostonmarathon.org/BostonMarathon/WelcomeBooklet.asp#hydration