Randomized, Double Blind, Placebo Controlled Comparison of Ritodrine and Hexoprenaline for Tocolysis Prior to External Cephalic Version at Term

Abstract

External cephalic versions in the study period were performed in a double blind design by 2 experienced practitioners. Sixty-three patients were allocated to treatment with either placebo, ritodrine or hexoprenaline. The main outcome measure studied was successful completion of external cephalic version. Hexoprenaline, but not ritodrine, was statistically more likely to be associated with successful version than placebo (p = 0.04 versus p = 0.22).

Outcome of labour after successful external cephalic version at term complicated by isolated transient fetal bradycardia

“…The commonest clinical complication reported after external cephalic version at term is the occurrence of transient fetal bradycardia, the incidence ranging from 0% to 40% (Table 1) 5–17 . There is a strong negative linear relationship between the reported incidence of transient fetal bradycardia and the total number of external cephalic versions (with logarithmic transformation) reported in each study ( r =−0.71, P = 0.006).…”

Arg16 homozygosity of the β2-adrenergic receptor improves the outcome after β2-agonist tocolysis for preterm labor

“…This degree of tachycardia was not expected with the use of hexoprenaline, which is specifically preferred for tocolysis because of its uterine ␤ 2 AR selectivity and has been shown to be the most chronotropically ␤ 2 -selective drug, having the least effect on the ␤ 1 -adrenergic receptors of the heart. 24,25 Our data do suggest that hemodynamic response cannot be used as a predictive "marker" of responsiveness to ␤-agonist stimulation because tachycardia was frequently noted in women in whom the uterine effect was poor and delivery occurred within 48 hours of tocolysis. The physiologic and pharmacologic functional differences between ␤ 2 AR genotype and haplotype variants have been the subject of many studies, and it must be noted that there is controversy as to the phenotypic behavior.…”

“…A large proportion of women became tachycardic, regardless of genotype or their tocolytic outcome. This degree of tachycardia was not expected with the use of hexoprenaline, which is specifically preferred for tocolysis because of its uterine β 2 AR selectivity and has been shown to be the most chronotropically β 2 ‐selective drug, having the least effect on the β 1 ‐adrenergic receptors of the heart 24 , 25 . Our data do suggest that hemodynamic response cannot be used as a predictive “marker” of responsiveness to β‐agonist stimulation because tachycardia was frequently noted in women in whom the uterine effect was poor and delivery occurred within 48 hours of tocolysis.…”

Variation of force applied during external cephalic version with different patients’ characteristic and outcome of version

“…Uterine relaxation using tocolytics may therefore not only increase the chances of procedure success 22 but also reduce the applied force, which may in turn reduce fetal side effects. In our protocol, we have been routinely using hexoprenaline as a tocolytic agent before performing the version 23. However, in 41% of cases it was commented on that the uterus was still not relaxed.…”