Puncturing the dura: a true clinical benefit or a distraction?

Abstract

The comparison of dural puncture epidural (DPE) labour analgesia with other accepted techniques including combined spinal-epidural (CSE) and epidural alone is an interesting and debated topic. The recent paper by Zang et al. attempts to address this and concludes there were no significant differences in the quality of labour analgesia for DPE compared with the CSE technique [1]. We have concerns regarding the methodology and results of this paper and its clinical significance for DPE-related trials.

First, the sample size calculation was assumed to detect a reduction in the composite primary outcome from 50% in the CSE group to 22.5% in the DPE group, based on previous calculations published by Chau et al. [2]. The most effective clinical interventions are, at most, modest in effect size [3], thus we argue that the authors used an overly optimistic prediction to calculate the minimum required sample size, which was done arbitrarily. A CSE vs. DPE would intuitively be a small effect size, thus using a small sample size would have insufficient power to evaluate this. Smaller effect sizes were most likely missed in this study due to the small sample size.

Second, the primary and secondary outcomes were all focused on parameters affecting an anaesthetist's workload, except for the final secondary outcome which was the satisfaction of the mother with labour analgesia. The satisfaction scores for both CSE and DPE groups ranged from 0 to 10, which we argue is a crude and non-discriminating outcome measure. Currently, there is a lack of patient-reported outcome measure (PROM) questionnaires to capture the quality of maternity care, especially during labour [4]. Future studies investigating the quality of analgesia will need to include maternity PROMs, specifically focused on the intrapartum period. Furthermore, Zang et al. did not capture the rate of caesarean deliveries after neuraxial labour analgesia, which is a key outcome concerning the patient, obstetrician and anaesthetist. We argue that future clinical trials need to include a core outcome set for holistic and accurate measurements, which also allows for meta-analysis and homogeneity in data collection between individual trials [5].

Finally, approaching the topic of labour analgesia from a holistic perspective, should we focus on the impact of an intentional dural puncture or access to labour analgesia? The clinical benefits of labour analgesia (regardless of technique) are well documented. Yet there are still disparities in access to labour analgesia, especially in socio-economically deprived parturients. A recent population-based study in Scotland found the utilisation of epidurals for labour analgesia was 22%, and women in the most deprived areas were 16% less likely to receive epidural analgesia compared with the most affluent [6]. When formulating research questions, do we aim for improving patient outcomes or optimisation? For future clinical trials that aim for clinical significance, instead of debating the benefits of puncturing the dura, maybe we can ask ourselves: how can we promote equity of access to labour analgesia to improve maternal health?