The uterine and cardiovascular effects of salbutamol and practolol during labour.

Intravenous salbutamol, a beta-adrenoceptor stimulant, given to nine patients in normal labour, with continous monitoring of uterine activity and of the maternal and fetal cardiovascular systems, was shown to decrease uterine activity significantly; maternal and fetal heart rates were significantly increased, and maternal systolic and diastolic arterial pressures were significantly decreased during the infusion, although no treatment had to be discontinued because of these effects. Apart from worsening of low back pain during the infusion in one patients, subjective side-effects were trival. With the salbutamol infusion continued at an effective maintenance rate, the carioselective beta-adrenoceptor blocking drug, practolol, given intravenously, reduced the maternal heart rate (although not significantly) but it did not alter the fetal heart rate; it also appeared to interfere transiently with the inhibiting action of salbutamol on uterine activity, but cerevical dilatation was arrested until the salbutamol infusion was discontinued. At least in five patients, labour remained suppressed until oxytoxin was infused intravenously.