Hyponatraemia in sport (Exercise-Associated Hyponatraemia)
“London marathon runner” – the headlines read – “left fighting for her life after drinking too much water …”
What is it?
Hyponatraemia simply put is having low salt levels. At any one time our body’s salt and sugar levels vary according to what we’re doing and what we’re consuming – and according to how well or ill we might be.
For the outdoors enthusiast there may come a time when we drink so much fluid that our sodium (salt) levels become overly diluted or we drink so much fluid that we essentially sweat out our salt to the point that we go into hyponatraemia.
If you ask a medic what causes this condition the first thing they’ll probably tell you is that it is very often caused as a side-effect of one drug or another. But for the casualty who is otherwise fit and healthy and enjoying the outdoors this is unlikely to be the reason.
The context for the outdoors enthusiast/endurance athlete is likely to be that of a hot day dealing with a casualty who has very diligently been drinking a lot of water. It can also occur in the casualty who is maybe on expedition in a foreign environment and who is dehydrated due to diarrhoea.
What does it look like? What do we see?
When our sodium levels are too low or too highly diluted, the cells in our brains swell up. In turn the casualty experiences symptoms that are associated with cerebral oedema (ie compression on the brain). When the brain is affected in this way the symptoms gradually manifest themselves in the casualty’s behaviour. Confusion, clumsiness, nausea, vomiting may all be seen. Initially though, nothing may be seen though the casualty will have at the very least, begun not feeling quite right.
In its later stages as the brain continues to be squeezed by this excess in fluid, things for the casualty get worse. Seizures, respiratory arrest and pulmonary oedema may all follow – all of which can have fatal outcomes.