Acute exercise- and drug-induced potassium shifts during pregnancy.

The exercise- and drug-induced potassium shifts in pregnant women was studied. Six healthy nonpregnant women, six healthy pregnant women and four hypertensive, pregnant women on labetalol performed a bicycle exercise test. Blood samples for plasma potassium concentrations were drawn before, during and after the exercise. The exercise-induced plasma potassium increase was 0.9 +/- 0.2 mmol/l in healthy control women and 0.8 +/- 0.1 mmol/l in healthy pregnant women. In hypertensive pregnant women on labetalol the increase was 0.3 +/- 0.3 mmol/l (P < 0.01). There was a negative correlation (r = 0.941, P = 0.05) between the plasma potassium and labetalol concentration. Our results suggest that the potassium exchange during normal pregnancy is not changed. Labetalol reduced the exercise-induced plasma potassium increase which contrasts to other beta-blocking agents which usually augment the plasma potassium increase caused by exercise.