Hyponatremia is also known as fluid overload. This occurs in hot climates when the athlete consumes too much plain water. 'Drink as much water as possible' is a common piece of bad advice given to athletes. Topping up sodium levels is just as important as replacing water lost in sweat, as lack of sodium can cause cells to swell. This cen be particularly harmful for brain cells.
However, the aim of consuming fluid is to replace that lost in sweat. The sweat we excrete during exercise also contains high levels of certain electrolytes, especially sodium (salt). It is important to keep stable and adequate levels of sodium in the body to maintain blood pressure and aid nerve and muscle functioning.
Drinking high levels of plain water in a bid to maintain hydration can be detrimental as sodium is not replaced and its concentration decreases. When sodium levels drop, water seeps inside cells to balance out the levels of sodium (principle of osmosis) and the cells swell. In most cells this is not a problem, however, brain cells cannot expand as the skull prevents this. Most symptoms of hyponatremia are caused by swelling of the brain cells.
Hyponatremia can also be a result of severe burns, heart failure, use of diuretics, kidney disease, and liver cirrhosis.
Symptoms of Hyponatremia
By far the most useful symptom in cases of hyponatremia following or during exercise is complaints of a swollen or bloated feeling. It can also often be noted that rings, bracelets etc are tighter than usual. Other symptoms include:
- Muscle weakness or spasms
- Nausea and vomiting
- Decreased consciousness
Treatment of Hyponatremia
Under no circumstances should the individual be given hypotonic or isotonic fluids (with lower or equal concentration to the blood). Individuals suffering from hyponatremia should be treated with some or all of the following interventions, dependant on the severity of the condition:
- Catheterisation to monitor urine production
- Intravenous hypertonic (3-5%) saline
- Salt tablets and sodium containing foods can be given
Possible Complications and Prevention
Hyponatremia can be a life-threatening condition if not treated in time. It can also result in brain herniation and coma.
Hyponatremia can be avoided by drinking sports drinks or home-made solutions which contain electrolytes (usually salt and sugar). Isotonic drinks are the best form of re-hydrating drink as they are the same concentration as the blood (approximately 4%).