We hear it over and over, Drink regularly and often, or even more ominously, Hydrate or Die. Instruction manuals, instructors and guides, and even wilderness medicine instructors emphasize the need for constant hydration. While this advice is true, it is possible to over-hydrate. Long exposure to heat challenge and/or over-hydrating during exercising, without replacing sodium lost from sweat, is a very bad thing. Hyponatremia is a condition resulting from sodium concentration levels in the blood dropping too low. In the athletic community this condition has been identified as a serious and common malady. An article titled, Hyponatremia among Runners in the Boston Marathon, in the April 14, 2005 issue of the New England Journal of Medicine puts more of a fine point by stating, Hyponatremia has emerged as an important cause of race-related death and life-threatening illness among marathon runners. The article detailed a study of runners in the 2002 Boston Marathon. Blood tests taken from 488 runners at the finish line found that 13 percent had hyponatremia. Running a marathon would probably cause my death from a variety of causes, but we should all pay attention to a condition that affects such a high percentage of trained athletes.

Signs and symptoms are dependent upon the patient and the amount of sodium lost. Mild to moderate signs and symptoms may include: Headache, nausea, possibly vomiting, dizziness or light-headedness, muscle cramps, mild confusion or anxiety, normal temperature and color, sweaty skin, and either a normal pulse, or very slightly elevated. These signs and symptoms, especially in a heat challenge environment, may erroneously lead the caregiver to assume heat exhaustion as the cause. Heat exhaustion is fluid volume depletion, which is treated by re-hydrating the patient. This will only make the hyponatremic patient worse. As the condition progresses the patient may become disoriented, irritable, and combative, and if unresolved, will eventually lead to seizures, unresponsiveness, and death.

The key to proper assessment and treatment is a complete and accurate patient history. Large amounts of fluids consumed and very little, or no food, lack of thirst, and regular urination that is clear and copious indicate hyponatremia and are different from those seen in heat exhaustion. A patient suffering from heat exhaustion would be thirsty and have darkly colored urine in low volumes.

Treatment for mild-to-moderate hyponatremia in a patient without an altered mental state needs to start immediately: No fluids, removal from the hot environment, and intake of salty foods. Introducing the food gradually will make it easier for the patient to tolerate. Be careful not to rely on electrolyte replacement drinks alone. They are low enough in sodium concentration that we are mostly adding water to our completely saturated patient. The condition is resolved when the patient re-develops their thirst, becomes hungry, and urine output becomes normal. Patients with an altered mental state must be evacuated to definitive medical care immediately.

Prevention is simple and easy: Eat! Salty snacks, crackers, trail-mix, along with regular meals will provide you with plenty of sodium to stave off hyponatremia. Dealing with a potentially life-threatening illness in the wilderness is always scary and difficult, and prevention should always be foremost in our backcountry decision-making, especially when prevention is so easy and fun: Just eat more food!