A randomized trial of epidural anesthesia to improve external cephalic version success.

Abstract:

Objective:This study was designed to determine whether epidural anesthesia would improve external cephalic version success in a safe and effective manner.

Study Design:. All women > 37 weeks gestation with breech presentation scheduled for external cephalic version at the medical center from Dec. 1, 1993, to July 31,1996, were randomized to receive an epidural or no epidural anesthesia. Under ultrasonographic guidance up to three version attempts were performed.

Results:Sixty-nine women were randomized to receive epidural (n=35) versus no epidural (n=34) anesthesia for external cephalic version. There were no statistically significant differences in maternal age, parity, maternal weight, gestational age, estimated fetal weight, or station of the presenting part. The success rate was better for the epidural group (relative risk 2.12, 95% confidence interval 1.24-3.62). Neither anterior placentation nor oligohydramnios affected the success rate.

Conclusion: Epidural anesthesia increases success of external cephalic version without any apparent detrimental effect on the maternal-fetal unit.

Commentary:

This is a very well designed and carried out research project. The authors are to be congratulated. The study is a randomized controlled trial which is being done to confirm a result previously obtained by other authors in a retrospective record analysis.

As we tend to deliver more and more breeches by cesarean, anything we can do to decrease the incidence of breech presentation will decrease our cesarean rate. The authors have studied a method to decrease the incidence of breech presentation at term. Over the years, I have always been admonished and admonished others not to use anesthesia for external cephalic version (ECV). The reasons for this were that with anesthesia, one would lose evidence of abruption or uterine rupture should they occur. Also that the mothers sensation of pain and discomfort would keep one from exerting too much force.

I was surprised when I found a paper by Friedlander reporting on 706 patients treated by ECV. In this study, all patients found to be breech were subjected to ECV regardless of the gestational age. ECV was performed anywhere from 20 weeks until the first stage of labor. If the ECV was unsuccessful, a consideration of general anesthesia was made. General anesthesia was used in 45 (13%) of those ECV’s done at 33 weeks or greater. The attempted version failed in 12 or 28% of these cases where anesthesia was used. The author thus reported a 98% overall success rate. There was a total of 14 of the 706 patients who delivered as breeches. So one can then say that 98% of all patients discovered to be breech at some time in their pregnancy were subsequently delivered as vertex presentations. Since the author does not tell us the total number of deliveries, we are unable to come up with a breech delivery rate for the total population. However we know that the incidence overall is about 3 %, therefore if only 2 % of the subgroup of those known to be breech were delivered that way, the method probably decreased the incidence of breech delivery. The author also reported no complications from the general anesthetics. He does not give a specific success or failure rate for patients at 35 or 37 weeks, he states that the failure rate increases with increasing gestational age.

A similar paper by Ranney also reports a very high success rate. In nearly 5000 patients cared for by Dr. Ranney over 21 years, he reduced the breech delivery rate to 0.56%. He did this by performing ECV on every fetus that he found to be breech from 25 weeks gestation on. Assuming a 3% incidence of breech in the population, he should have had 146 breeches. He had only 27. Therefore he prevented 119 breech deliveries. In order to do this he performed 1240 ECV’s on 860 fetuses. In other words 7 out of eight of the fetuses would have turned without any assistance. Dr. Ranney used neither tocolysis nor anesthesia. He also reported no evidence of maternal or fetal damage. He does not give specific failure rates for 35 or 37 weeks. He does state that the optimal time for successful version is on or before the 34^th week.

Due to the study design of the paper being discussed, it is not possible to get the same numbers from their data. However by making a few assumptions, we might come close. If all patients who are breech at 37 weeks remain breech and if ECV with tocolysis and epidural has a 2/3 success rate as in this study and if ECV with tocolysis has a 1/3 success rate as it did in this study, then ECV with tocolysis at 37 weeks will decrease breech delivery from 3% to 2% and ECV with epidural and tocolysis will decrease breech delivery from 3% to 1%.

In order to have a 3% breech delivery rate, we need to do no ECV’s.

In order to have a 2% breech delivery rate, we need to attempt ECV on all breeches at 37 weeks with tocolysis.

In order to have a 1% breech delivery rate, we need to attempt ECV on all breeches at 37 weeks with tocolysis under epidural anesthesia.

Based on the above data and the data of Carlan et al, I feel that the best course to reduce the incidence of breech delivery at term is to perform ECV at 37 weeks under tocolysis and epidural anesthesia. In order to prove this, I feel that more studies should be carried out. These should look at things like; are the results changed if one starts without an epidural and then does the epidural only on those patients in whom successful version can not be attained without an epidural? What are the long term effects of the epidural e.g. incidence of low back pain?

Although all of the papers mention the effects of placental location and amniotic fluid volume, none of them give the incidence of or the effects of uterine anomalies on success rates of ECV.

Again Schorr et al are to be congratulated on a fine piece of work and hopefully we will see further studies on this procedure.

References:

Am J Obstet Gynecol 1997;177:1133-7