The renin-aldosterone system and electrolyte balance during tocolytic therapy

The effects of short and long-term tocolytic therapy, with salbutamol on renin activity, aldosterone levels, sodium and potassium concentration in urine, blood, and red blood cells in 44 pregnant women were studied. No significant changes were observed in renin activity and aldosterone levels between the 1st and 5th days of i.v. or p.o. therapy and in 24-h sodium urinary excretion. Serum potassium levels significantly decreased by the 2nd and 4th h from start of i.v. infusion of salbutamol, returning to preinfusion levels within 24-36 h, whereas no concomitant increase in red cell potassium levels was detected. Urinary potassium excretion showed significant decrease within 24 h from start of i.v. therapy, returning to control levels after 48 h. No change in sodium concentration in blood and red blood cells was observed.