Hypoelectrolytemia and metabolic alkalosis in infants with cystic fibrosis.

The records of all children in the Tucson area diagnosed as having 
cystic fibrosis (CF) before the age of 12 months were reviewed 
to ascertain the prevalence of metabolic alkalosis as a major presenting 
manifestation of CF. Five of eleven infants (46%) in whom CF 
had been diagnosed between 1 and 12 months of age initially 
were seen with hypokalemia, hypochloremia, and metabolic alkalosis unassociated with marked 
dehydration, hyperpyrexia, or major pulmonary and/or gastrointestinal symptoms. Two infants had 
repeated episodes of metabolic alkalosis; for one of these infants, both 
episodes of metabolic alkalosis occurred before the diagnosis of CF. It 
is postulated that chronic loss of sweat electrolytes together with mild 
gastrointestinal or respiratory illness may predispose the infant with cystic fibrosis 
to a severe electrolyte and acid-base disturbance. The lack of shock 
and hyperpyrexia together with the apparent chronicity of electrolyte losses differentiates 
metabolic alkalosis from the heat prostration syndrome, a more acute complication 
of cystic fibrosis. Quantitative sweat testing should be part of the 
evaluation of any infant with unexplained metabolic alkalosis. Serum electrolytes should 
be assessed regularly in infants with cystic fibrosis during hot weather 
months. 