Serum and urinary cation changes on acute induction to high altitude (3200 and 3771 metres)

Twenty subjects each were rapidly inducted by road to 3200 ad 3771 m. Serum and urinary sodium, potassium, calcium, and magnesium were measured during 10 d at high altitude. At 3200 m, only serum potassium increased significantly on the 10th day. At 3771 m, serum potassium did not increase. Serum sodium generally remained low, serum magnesium increased, while calcium decreased significantly. Urinary volume over 24 h decreased more and for longer duration at 3771 m than at 3200 m. Urinary cations did not change significantly at 3200 m. At 3771 m, sodium and potassium excretion decreased on days 1 and 3 later returned towards preinduction levels. Magnesium and calcium decreased throughout the high-altitude stay. Significant changes were noticed in serum and urinary cations on exposure to high altitude when adequate caloric intakes were not ensured.