In the mid-afternoon, one of the passengers begins to complain of fatigue and stomach discomfort. Fearful that she is suffering from heat illness and dehydration, the guides instruct her to drink water. More water is also given to the other passengers as a preventative measure.
At noon on the third day, the woman is airlifted to a hospital with diarrhea, vomiting, and confusion. A mere 2 hours later, a second woman begins to complain of nausea. She suddenly becomes disoriented and suffers a grand mal seizure. She is also evacuated by helicopter that very same day.
That evening, at camp, a third woman abruptly begins to vomit and quickly becomes unresponsive. She remains unresponsive and vomiting throughout the night. A helicopter finally reaches camp in the morning and successfully evacuates the third patient.
What caused these three women to become so ill?
The guides were very focused on preventing dehydration and other related heat illness and thus encouraged an excessive intake of water. The suggestion to drink more made the situation worse.
But entire blame can not be placed on the guides. After all, the early symptoms of hyponatremia such as nausea, vomiting, headache and fatigue are similar to many other illness like dehydration or heat exhaustion. In environments like that of the Grand Canyon, dehydration and heat exhaustion are much more common than hyponatremia. More water would probably be the reaction of many.
Unfortunately, no one investigated exactly how much water had been consumed by the three women. If they had, then maybe hyponatremia would have made it on to the radar.
The final confusing factor was that all three women experienced a decrease in urine output. Normally, this is seen as a red flag for dehydration. However, hyponatremia causes the release of a hormone responsible for water retention and decreased urination. Despite the excessive amount of water intake, individuals can still have very little urine output.
So what are the best ways to spot hyponatremia? The best way is to find out how much water the patient has ingested within the 24 hours leading up to the onset of symptoms. Ask the person or members of their group. This information will be helpful when trying to distinguish between dehydration and hyponatremia.
Drinking water only when thirsty can reduce the likelihood of over hydration and the development of hyponatremia. If hyponatremia seems probable, reduce water consumption and have the individual drink a mix of 3-4 bouillon cubes dissolved in 125ml water.
Thankfully, the story ends happily for all three women. After intensive care and close monitoring, they were released from the hospital without serious life-lasting consequences. You can read about the full details of their experience here: http://www.wemjournal.org/article/S1080-6032(14)00267-1/pdf
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