Hyponatremia Associated with Overhydration in U.S. Army Trainees

Karen K. O'Brien, Scott J. Montain, William P. Corr, Michael N. Sawka, Joseph J. Knapik, Stephen C. Craig
2001 Military medicine  
This report describes a series of hyponatremia hospitalizations associated with heat-related injuries and apparent overhydration. Data from the U.S. Army Inpatient Data System were used to identify all hospitalizations for hyposmolalityl hyponatremia from 1996 and 1997. Admissions were considered as probable cases of overhydration hyponatremia if this was the only, or primary, diagnosis or if it was associated with any heat-related diagnosis. Seventeen medical records were identified, and the
more » ... ents leading to hospitalization were analyzed. The average serum sodium level was 122 ± 5 mmollL (range, 115-130 mmollL). All 17 patients were soldiers attending training schools. Seventy-seven percent of hyponatremia cases occurred in the first 4 weeks of training. Nine patients had water intake rates equal to or exceeding 2 quarts per hour. Most patients were in good health before developing hyponatremia. The most common symptoms were mental status changes (88%), emesis (65%), nausea (53%), and seizures (31%). In 5 of 6 cases in which extensive history was known, soldiers drank excess amounts of water before developing symptoms and as part offield treatment. The authors conclude that hyponatremia resulted from too aggressive fluid replacement practices for soldiers in training status. The fluid replacement policy was revised with consideration given to both climatic heat stress and physical activity levels. Field medical policy should recognize the possibility of overhydration. Specific evacuation criteria should be established for exertional illness.
doi:10.1093/milmed/166.5.405 pmid:11370203 fatcat:kgdoa4kzcvfi5ajyfunw3agf3i