- Mitchell H Rosner, MD
Mitchell H Rosner, MD
- Professor of Medicine
- University of Virginia Health System
- Tamara Hew-Butler, DPM, PhD
Tamara Hew-Butler, DPM, PhD
- Associate Professor, Exercise Science
- Oakland University
Severe and potentially life-threatening hyponatremia can occur during or following exercise, particularly in athletes participating in endurance events such as marathons (42.2 km), triathlons (3.8 km swim, 180 km cycling, and 42.2 km running), and ultradistance (100 km) races [1-4]. A similar problem can occur during short-duration exercise (eg, American football), military operations, and desert hikes.
Exercise-associated hyponatremia (EAH) was first described in Durban, South Africa in 1981 and in 1985 in four athletes participating in endurance events longer than seven hours . Prior to 1981, athletes were advised to avoid drinking during exercise, leading to the development of hypernatremia in some athletes [6,7]. Subsequently, athletes were advised to consume as much fluid as possible during exercise. Concomitant with these recommendations, the incidence of hyponatremia in endurance athletes appeared to increase, particularly in the United States.
The majority of athletes who develop hyponatremia are asymptomatic or mildly symptomatic (eg, weakness, dizziness, headache, lethargy, nausea/vomiting). However, severe manifestations can occur, including seizures, cerebral edema, noncardiogenic pulmonary edema, and death. (See 'Clinical manifestations' below and "Manifestations of hyponatremia and hypernatremia in adults".)
The 2015 Third International Exercise-Associated Hyponatremia Consensus Development Conference defined exercise-associated hyponatremia (EAH) as hyponatremia (serum or plasma sodium below the normal reference range of the laboratory) occurring during or up to 24 hours after prolonged physical activity .
Prior to the recognition that drinking large volumes of water can lead to potentially fatal hyponatremia, it was not rare for endurance athletes to be hyponatremic at the end of the race, usually in the absence of overt central nervous system symptoms [1,2,9-17]. The incidence of hyponatremia has varied, ranging from 0 to 18 percent in marathoners and triathletes [2,10,14-16] to 51 percent of runners participating in a 161 km mountain footrace, which suggests that exercise-associated hyponatremia (EAH) may be more prevalent in extreme endurance events lasting more than 24 hours .
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- RISK FACTORS
- High fluid intake
- Increased fluid intake
- Persistent secretion of ADH
- Role of exchangeable sodium stores
- Sweat sodium loss
- CLINICAL MANIFESTATIONS
- Relation to serum sodium
- The collapsed athlete
- General principles
- - Mild to moderate symptoms
- - Severe symptoms
- Use of hypertonic saline
- - Rate of correction
- INFORMATION FOR PATIENTS
- SUMMARY AND RECOMMENDATIONS