Poisoning by Water

As any toxicologist will tell you, and as most of us know, too much of a good thing - or in toxicology, too much of just about anything can be bad. Whenever I introduce students to toxicology, I usually begin with very accessible examples, like anti-inflammatory medication. I also like to use personal examples whenever possible, like the time our dog Bruno, after placing himself in front of a van and winding up with a broken leg and a severely dislocated hip – decided to consume a whole bottle of doggie anti-inflammatory medication, blue plastic and all. To his defense the things were disguised as meaty treats, and after getting his stomach pumped, and kidney and liver function tested, all was well.

Another example is that of water, although, having too much water always seemed a bit far-fetched. That is, until this past weekend when my husband Ben, almost passed on to hilly bicycle heaven – after a bout of water poisoning – or hyponatremia. I might sound glib about this now, but perhaps that’s to assuage my own anxiety over potentially loosing someone I love to something so preventable.

In his case, he didn't just drink too much water, he lost too much sodium. He might be described as a passionate biker. When he rides the seven miles to work, he takes the long way home, logging twenty to forty miles a day. When he rides on weekends he takes the long way to anywhere, riding from thirty to sixty miles. When he rides for fundraisers, he chooses the 100 mile ride – or in this case the 120 mile, 10,000 feet of climbing, dirt road ride. In other words, riders like Ben are not like you and me (well at least not like me – these days, fifty is my limit.)

Now Ben is an experienced rider, who knows to watch his water and electrolyte intake. Electrolytes are ions that exist in solution and include sodium, potassium, calcium, and chloride. In our blood these ions and others are essential for normal cell function. You might be familiar with the multitude of electrolyte replacement drinks available in a range of wholly unappetizing colors (Neon Green, Antifreeze blue etc.) marketed to both the general public and to athletes. The idea is when you exercise you sweat out not just water but electrolytes, and so you need to replace accordingly (they also contain carbos for energy I suppose.)

What Ben didn’t know on that fateful day was how carefully to watch that balance, and that riding over 100 miles, on a steamy August day (one of the most unbearable of the summer), though the hilltowns of western Massachusetts, would not only wring the salt right out of him, but also cause him to over drink. Though he quaffed electrolyte drinks, and consumed little powdery packets of the stuff, none of it had sufficient amounts of sodium to maintain the balance.

The result? An ambulance trip to the ER, an overnight stay in the hospital, one very concerned wife. When the nurses asked simple questions like, “Where are you?” “What month is it?” “When is your birthday?” he was unable to respond (though he didn’t miss a beat when she inquired about our current president, Dubya, an unfortunately tough thing to forget.)

Turns out, his sodium concentration had fallen to below 121 milliequivalents per liter (mEq/L) of blood. The normal range is 136 to 145 mEq/L, and anything below that is considered hyponatremia. Ben had a severe case of hynonatremia. Proper sodium (and other electrolytes) concentration in the blood is essential for life, and keeps our cells in balance with the fluids that surround them. When the sodium concentration in our blood becomes too dilute, the cells take up water, causing them to swell. Hence, Ben’s swollen brain forgot most things. In the worst cases seizure and death can result.

Thankfully, Ben was plugged into a saline I.V. drip moments after the ambulance arrived. Several I.V. bags later, he could finally recall our kids ages, state that he was indeed in the hospital and recall our anniversary date (well, he missed by eleven days but at this point who’s counting?)

So, there you have it – an unfortunately personal but thankfully nonfatal example of poisoning by water. Hopefully his tale and the articles below will help others avoid his fate.

For more about hyponatremia, warning signs, and how to prevent, check out the following sites:

Salt and the Athlete

Fluid Balance and Electrolyte Balance and Endurance Exercise: What can we learn from recent research?

Hyponatremia, Mayo Clinic

New Statement on Exercise-Associated Hyponatremia Issued