Neuraxial block and success of external cephalic version

Introduction

Term singleton breech pregnancy may be managed by vaginal breech delivery. However, most women with a breech presentation undergo planned Caesarean delivery.

An alternative management strategy is external cephalic version (ECV), which if successful, can enable vaginal cephalic delivery that is safer, and so potentially avoids maternal morbidity associated with Caesarean delivery.¹ The reported success rates of ECV vary, with one meta-analysis reporting a pooled success rate of 59% and a complication rate of 6.1%.²

Possible adverse effects associated with ECV include abnormal fetal HR monitoring, vaginal bleeding, placental abruption, maternal-fetal transfusion, emergent Caesarean delivery and perinatal mortality. External cephalic version should be attempted in a setting where prompt Caesarean delivery is possible.

In this article we discuss ECV, with a focus on anaesthetic techniques including neuraxial blockade, systemic sedation and analgesia that may contribute to successful ECV.

Neuraxial block

Neuraxial block reduces maternal discomfort and improves success rates of ECV, probably by improving the mother's ability to tolerate ECV, and facilitating ECV by relaxation of the abdominal wall musculature. The term neuraxial block includes both surgical anaesthesia and analgesia (for pain relief). A meta-analysis of six RCTs by Lavoie and Guay compared neuraxial block with no block.³ These trials reported spinal doses ranging from bupivacaine 2.5–7.5 mg with fentanyl, and epidural doses of lidocaine 2% titrated to the T6 dermatomal level. The meta-analysis reported increased ECV success rates with neuraxial block (59.7% compared with 37.6%; pooled relative risk 1.58; 95% confidence interval [CI] 1.29–1.93).³ The number needed to treat to achieve one additional successful ECV was five. All the RCTs included used tocolytic therapy. All but one RCT compared neuraxial block with no analgesia; one used i.v. fentanyl analgesia as the comparison group.

The optimal modality (spinal intrathecal, epidural or combined technique) and the optimal dose for improving ECV success rates remains unknown. Lavoie and Guay reported a higher success rate with epidural compared with spinal block (91% vs 46%).³ The likelihood of successful ECV was almost two-fold higher with epidural anaesthesia (relative risk (RR) 1.91, 95% CI 1.29–1.93) compared with 1.5-fold higher with spinal anaesthesia (RR 1.46, 95% CI 1.14–1.87). However, this difference was not statistically significant as evident from the overlapping confidence intervals. To date no study has directly compared epidural with spinal analgesia for ECV. Regarding the effective dose, a recent RCT compared four doses of spinal bupivacaine (10, 7.5, 5 and 2.5 mg + fentanyl 15 μg) and concluded that doses above 2.5 mg offered no additional benefit for ECV success rate or prevention of Caesarean deliveries.⁴ This study reported a mean sensory level of T6 and adequate abdominal wall relaxation in all groups. While lower doses of spinal anaesthesia may suffice for ECV and facilitate an earlier discharge, a larger dose of spinal bupivacaine would facilitate an emergency Caesarean delivery if needed.

Concerns about excessive force applied to the fetus when using neuraxial block have been raised. One study investigated the manual force applied when neuraxial anaesthesia was given before ECV, and reported that the force applied to the fetus appeared lower when neuraxial anaesthesia was used.⁵ After a failed attempt of ECV, using neuraxial blockade for a second attempt offered a 39% success rate and a reduction in the rate of Caesarean delivery from 100% to 64%.⁶

Aside from maternal hypotension, the rate of other complications of ECV does not appear to be affected by use of a neuraxial block.³

Systemic analgesia for ECV

Several studies evaluated the use of systemic analgesia and sedation for ECV. The rationale is that analgesia and sedation may reduce abdominal guarding and facilitate ECV. One RCT included 152 nulliparous women, and the primary outcome was analgesia.⁷ Remifentanil was administered as a continuous infusion at 0.1 μg kg⁻¹ min⁻¹ with additional boluses of 0.1 mg kg⁻¹ on demand. The study reported lower numerical pain scores in the remifentanil group (remifentanil 4.6   [sd 2.6] vs placebo 6.5 [ 2.7]; p<0.001) and success rates for ECV (remifentanil 56.5% vs placebo 39.5%; p=0.04).⁷

A study comparing spinal anaesthesia, i.v. remifentanil and placebo found that analgesia with remifentanil was less efficacious than spinal anaesthesia.⁸ The mean numerical pain score was 35 in the remifentanil group, zero in the spinal anaesthesia group and 50 in the control group (p<0.001). Success rates of ECV were similar in the remifentanil and placebo groups (64% in both), compared with 83% in the spinal group (p=0.027).⁸ Maternal complications such as nausea and pruritus with remifentanil were reported infrequently.

Obstetric complications were not reported in these studies, although the sample sizes were small and they were underpowered to provide meaningful information about their frequency. There is currently insufficient evidence regarding the efficacy of remifentanil analgesia to improve the success of ECV. Nevertheless, it appears suitable for analgesia, particularly if neuraxial blocks are contraindicated.

Nitrous oxide was also evaluated as an analgesic modality to facilitate ECV. One study found no difference in ECV success rate in 150 women, although there was a significant difference in a subgroup of 68 multiparous women (47.1% vs 23.5%, p=0.042). Pain levels did not differ significantly between the two groups.⁹

Summary

Based on the data available currently, neuraxial block appears to facilitate successful ECV. The optimum dose and block (epidural or spinal) are yet to be defined. The dose selection should include considerations such as anticipated spinal-induced hypotension, block level and presence of block for a prompt Caesarean delivery.

If the aim is analgesia, remifentanil PCA is useful to reduce pain and might offer some benefit in ECV success rate. The currently available data do not support the use of nitrous oxide analgesia for ECV.

To improve cost effectiveness, institutions may consider different logistical arrangements. A first attempt of ECV may be performed as a bedside manoeuvre (with or without remifentanil analgesia), with the following attempt performed in the operating room under spinal anaesthesia in order to proceed to a planned Caesarean section if ECV fails. Alternatively, first attempts could be performed with low dose spinal or epidural analgesia. The use of a combined spinal/epidural technique with a low initial spinal dose could facilitate an earlier discharge after a successful ECV, and enable prompt Caesarean delivery with epidural anaesthesia if needed.

Declaration of interests

The authors declare that they have no conflicts of interest.

Biographies

Carolyn Weiniger is an attending anesthesiologist in the Department of Anesthesia, Critical Care and Pain Medicine at the Tel Aviv Medical Center, Sackler School of Medicine, Tel Aviv Israel where she is Director of the Obstetric Anesthesia Unit. She has authored over 70 original research papers, reviews and chapters, mainly related to safe practices including respiratory depression associated with opioid administration, external cephalic version and placenta accreta, serves as an Editor of the International Journal of Obstetric Anesthesia, and Chair of the Obstetric Anaesthesiology Subcommittee of the European Society of Anaesthesiologists.

Victor Rabkin is a resident in the Department of Anesthesia, Critical Care and Pain Medicine at the Tel Aviv Medical Center, Sackler School of Medicine, Tel Aviv Israel.

Matrix codes: 1D02, 2B01, 3B00