Preliminary observation of impaired water excretion in treated status asthmaticus
R. Singleton, D. I. Moel and R. A. Cohn
Patients in status asthmaticus often have elevated plasma antidiuretic
hormone levels. To determine if children in status asthmaticus have
impaired water excretion and an increased risk of developing significant
hyponatremia when given a fluid challenge, five consecutive patients who
showed moderate asthmatic symptoms after taking two doses of epinephrine
hydrochloride were given a fluid challenge (20 mL/kg of 5% dextrose in 0.2%
normal saline solution given intravenously over 30 minutes followed by
maintenance fluids [1,500 mL/sq m/24 hr] for 50 minutes). Urine was
collected at 20-minute intervals for measurement of free-water clearance
and percent water-load excretion in 80 minutes. This protocol was repeated
24 to 48 hours later, after clinical improvement. None of the patients was
hyponatremic during status asthmaticus before water loading. However, four
of five patients were mildly hyponatremic (serum sodium level between 130
and 132 mEq/L) between status asthmaticus and after clinical improvement.
These same four patients also became mildly hyponatremic after fluid
challenge during status asthmaticus. Maximal free-water clearance and
percent water load excretion in 80 minutes were significantly lower during
status asthmaticus after fluid challenge compared with results obtained
after water loading when the patients' conditions were clinically improved.
We conclude that patients in status asthmaticus have impaired water
excretion after water loading but with a small risk of significant
hyponatremia; a patient remaining in status asthmaticus and given large
volumes of hypotonic fluid over a prolonged period of time may be at higher
risk for significant hyponatremia.
