Compared to high-dose epidurals where mobility is impossible, mobile epidurals have been shown to reduce instrumental vaginal delivery rates. The mechanism for this benefit may depend on women walking or adopting upright postures during labour. We investigated maternal motor power and ambulation of 1052 primparous women randomised to high-dose epidural (Control), Combined Spinal Epidural (CSE) or Low-Dose Infusion (LDI) as a pre-specified, secondary outcome of the Comparative Obstetric Mobile Epidural Trial. Modified Bromage power scores and the level of mobility a woman actually achieved were recorded each hour after epidural placement during first and second stage, until delivery. Relative to control, significantly more women maintained normal leg power throughout labour in both mobile groups and significantly more women with CSE maintained superior leg power for longer than with LDI. Observational analysis did not demonstrate an association between the level of ambulation a woman actually achieved after epidural placement and delivery mode.

◊ Reviewed by M. Van de Velde, MD, PhD
Professor, Department of Anaesthesiology, U.Z. Leuven, Leuven, Belgium

 The present trial is a secondary analysis of a pre-defined secondary outcome parameter of the so-called COMET trial. This trial compared conventional high-dose epidural analgesia (bupivacaine 0.25% bolus of 10 mL at maternal request) versus low-dose infusion (loading dose of bupivacaine 15mg with fentanyl followed by bupivacaine 0.1% with fentanyl at 10 mL/hour) and Combined Spinal Epidural (CSE) analgesia (spinal initiation with 2.5 mg bupivacaine and fentanyl followed by bupivacaine 0.1% with fentanyl at 10 mL boli) to asses quality of analgesia and labour outcome. More than 1000 women were randomized to one of the three study groups. Previous publications have reported on the results of this trial (1,2).

The COMET study is a well designed, well executed large trial clearly demonstrating the benefits of low-dose epidural techniques. With CSE and low-dose infusion more women maintained normal motor power as compared to high-dose conventional epidural analgesia. CSE preserved motor function longer than low-dose infusion and resulted in more women ambulating during the second stage of labour. Mobility during the second stage of labour resulted in more spontaneous vaginal deliveries.
This trial provides considerable evidence that reducing motor impairment with CSE or low dose infusion techniques is effective in increasing the spontaneous delivery rate following regional analgesia for labour. The study also gives evidence that ambulation increases the likelihood of a spontaneous delivery. The study also indicates, and this is the conclusion of the authors, that CSE whilst producing highly effective analgesia offers the best possible chance to women to maintain normal motor function, ambulate throughout labour and possibly increase the spontaneous delivery rate.

This reviewer feels that yet other advantages of CSE over conventional epidurals are put forward by this study.  Other clear advantages are rapid analgesia, increased epidural catheter reliability, reduced local anaesthetic consumption, reduced motor block and increased patient satisfaction.

◊ References.

1. Wilson MJ et al.
   Urinary catheterization in labour with high-dose versus mobile epidural analgesia: a randomized controlled trial. Br J Anaesth 2009; 102, 97 – 103.
   
   
2. Wilson MJ et al.
   Randomized controlled trial comparing traditional with two mobile epidural techniques: anesthetic and analgesic efficacy. Anesthesiology 2002; 97, 1567 – 1575.