Frequency and significance of electrolyte abnormalities in pneumonia.

To determine the frequency of electrolyte disturbance in pneumonia, we studied 264 hospitalized children with pneumonia for serum sodium and potassium concentration, and plasma osmolality (Posm) on the day of admission. Urine osmalality (Uosm) and urine spot sodium concentration were measured in those who had a serum sodium less than or equal to 130 mEq/L. Hyponatremia was found in 27%, hypernatremia in 3.7%. Hypokalemia (serum potassium less than or equal to 3.5 mEq/L) in 19 and 2% had hyperkalemia (serum potassium greater than or equal to 6.5 mEq/L). Of all the hyponatremia, 68% were secondary to syndrome of inappropriate ADH secretion (SIADH) as suggested by a concomitant lowering of Posm less than or equal to 280 mosm/kg and increased urinary osmolality and sodium excretion. Hyponatremia was associated with 60% longer hospital stay, two fold increase in complications and the 3.5 times higher mortality compared to that of normonatremia. The above variables were affected further, if hypokalemia coexisted with hyponatremia.