Water intoxication in asthma assessed by urinary arginine vasopressin.

A 3-year-old girl with status asthmaticus developed a grand mal seizure in association with hyponatraemia after 16 h of fluid therapy. Urinary arginine vasopressin (AVP) was elevated during the attack and rose strikingly before the onset of the convulsion. In 13 of 17 other patients with moderately severe asthmatic attacks, increases in urinary AVP levels occurred before the initiation of treatment. Dilutional hyponatraemia (water intoxication) must be prevented in patients with severe asthmatic attacks in whom diuretic capacity is impaired.