A double blind, randomized trial on augmentation of labour with a combination of intravenous propranolol and oxytocin versus oxytocin only

Abstract 

Objective

To compare the combination of intravenous propranolol and oxytocin with oxytocin only in augmentation of labour.

Study design

A prospective randomized double-blind study in an obstetric department of a large university hospital in Finland. A total of 107 parturients with arrested first stage of labour owing to inadequate uterine contractility were randomized to receive intravenously once or twice a 2mg dose of propranolol or placebo combined with oxytocin infusion. The main outcome measure was the effect of intravenous propranolol on the frequency of Caesarean section among parturients with arrested labour. The secondary outcome measures were the duration of labour, the required dosage of oxytocin, CTG readings, neonatal outcome and maternal and cord plasma levels of β-adrenoceptor-binding component of propranolol. Categorial variables between the groups were compared using Chi square and Fisher's exact tests. Continuous variables were compared using the Mann–Whitney U-test and Student's t-test.

Results

No reduction in Caesarean section rate was found in the propranolol group. Seventy-three percent of the parturients in the propranolol group and 85% in the placebo group had spontaneous vaginal delivery, RR=0.86 (95% CI 0.70–1.05). The percentage proportion of the augmented part of labour was significantly shorter in the propranolol group than in the placebo group. No differences in the required oxytocin dosage or CTG pathology were found between the groups. Propranolol was found to be safe for the neonates. The concentrations of its β-adrenoceptor-binding component after a 2mg intravenous dose were quite similar in parturients and neonates at the time of delivery. The active drug component crossed placental barriers with an average neonate umbilical artery/parturient venous plasma ratio of 0.7. After a 4mg dose the active drug concentrations in parturients were rather similar to those measured after 2mg dose, whereas in neonates there were signs of drug accumulation. No picture could be obtained from the kinetics of the β-adrenoceptor-binding component of propranolol from the data.

Conclusions

Propranolol (2 or 4mg i.v.) combined with oxytocin, as treatment for arrested labour did not affect the Caesarean section rate compared with placebo plus oxytocin. The percentage proportion of the augmented part of labour was significantly shorter after propranolol. Propranolol was safe for the neonates and can be used as an additional medication among parturients with arrested labour.

Abbreviations: bpm, beats per minute, CS, Caesarean section, CTG, cardiotocography/cardiotocographic, IU, international unit, MAP, mean arterial pressure, NICU, neonatal intensive care unit

Keywords: Arrested labour, Dystocia, Propranolol, Oxytocin, Augmentation of labour