The heat of the day is oppressive, but you’ve taken care to bring along a full Camelbak plus a couple of extra bottles of water. A nice apple lines your pack. You’ve been sweating profusely. This does not faze you because you follow the rule of drinking water before you need it. So you know that you are well-hydrated and you still have plenty to drink.
Then it hits you: a headache combined with nausea. Oh, this is easy, you say to yourself. “I’ll just drink more water.” You slake your thirst but the headache and nausea do not go away as they usually do. Hmm. Maybe you need something to eat? You pull out your apple and reduce it to its core. The syndrome is getting worse. You throw up your emergency meal and the water you drank. What is going on?
Hiking writers always warn us to bring plenty of water and extra food when we go on a hike because dehydration and hypoglycemia are real killers. I’ve had my share of bad experiences due to lack of these. Once I needed to be airlifted off the north slope of Silverado Canyon on a day when it was so hot that the soles of my wife’s boots melted off. I threw up a mile and a half up the mountain. Going on would have killed me. There have been times when my diabetes medicines were titrated too high and I found myself starving due to glucose depletion. This sort of thing can happen to nondiabetics, too. A woman who I was working with on the Native Seed Farm felt a headache and nausea come on. Drinking water didn’t help. I thought about the situation and asked her when she had last eaten. Turned out that she had skipped dinner the night before and had only a piece of toast for breakfast. A few glucose tablets later she felt fine.
The trouble with knowing why you suddenly have a headache is that so many similar conditions brought on by exercise have similar symptoms:
The last of these — hypoatremia — is the unsung killer of outdoors people.
Hypoatremia distinguishes itself from dehydration and hypoglycemia (low blood sugar) by additional symptoms including lethargy, loss of appetite, restlessness, irritability, muscle spasms, and seizures culminating in a coma. We may not think much of early warning signs such as loss of balance resulting in falls, slouching, changes in how we walk, and difficulty in paying attention. Insufficient sodium plasma causes the cell walls of the neurons to allow water to enter. They swell, causing the brain to come up against the interior of the skull. The strain leads to the intensifying of the headache, nausea, and vomiting, the collapse of brain function, respiratory arrest, and the filling of the lungs with fluid (pulmonary edema).
How does this happen? Each of us carries a red ocean inside of us. We are dependent on its electrolytes to maintain the structure of our cells. Without it, our brain cells explode.
One thing to remember is that when you start to exercise, sodium levels actually go up as you dehydrate. This is simply because the salt concentrates in the dwindling amount of water in your system. A small amount of salt leaves your pores along with the water, however: when you chug down your H2O, you replace the water but not the salt. Repeating this process over several hours leads to a serious deficiency and the appearance of the symptoms named above. If all you are thinking about is getting enough water, you may compound the problem by drinking still more water, paving the way for neurological damage and possibly death.
Since treatment calls for saline IVs, prevention is the key. You can try drinking less water, but this is a tricky proposition because too little water can also lead to a call to the mortician. The best course is to prime yourself with salty foods. These will help you self-balance your electrolyte levels by making you thirsty when you have had too much. Plus they are more pleasurable than the second option which is salt tablets. I keep these in my backpack nonetheless because much of my hiking is done on days exceeding 85°F (30°C) and I sweat a lot. Manufacturers advise consuming one salt tablet every hour — with water. I find the best approach to a headache or nausea is to treat myself for dehydration, low blood sugar, and hypoatremia at the same time. Gatorade® and similar sports drinks offer an excellent all-around menu item for the hiker who thinks like this. Chowing down on pretzels helps, too. Check the nutrition labels of your favorite snacks for information on how much sodium they contain.
I’ve included links to ,more detailed references about hypoatremia below. Read them carefully and talk to your doctor about appropriate actions that you can take to avoid water toxicity. Remember to carry not only sufficient water, but also sources of salt and carbohydrates. Be safe.
- Hypoatremia (Wikipedia)
- Wilderness Medical Society Practice Guidelines for Treatment of Exercise-Associated Hyponatremia
- The Math of Salt Loss
- Salt and the ultraendurance athlete