Comparison of ultra-low, low and high concentration local anaesthetic for labour epidural analgesia: a systematic review and network meta-analysis

Abstract

Lumbar epidural is the gold standard for labour analgesia. Low concentrations of local anaesthetic are recommended. This network meta-analysis investigated whether further reducing the concentration of local anaesthetic can improve maternal and neonatal outcomes without compromising analgesia. We conducted a systematic search of relevant databases for randomised controlled trials comparing high (>0.1%), low (>0.08% to ≤0.1%) or ultra-low (≤0.08%) concentration local anaesthetic (bupivacaine or equivalent) for labour epidural. Outcomes included mode of delivery, duration of labour and maternal/neonatal outcomes. Bayesian network meta-analysis with random-effects modelling was used to calculate odds ratios or weighted mean differences and 95% credible intervals. A total of 32 studies met inclusion criteria (3665 women). The total dose of local anaesthetic received increased as the concentration increased; ultra-low compared with low (weighted mean difference -14.96 mg, 95% credible interval [-28.38 to -1.00]) and low compared with high groups (weighted mean difference -14.99 [-28.79 to -2.04]), though there was no difference in the number of rescue top-ups administered between the groups. Compared with high concentration, ultra-low concentration local anaesthetic was associated with increased likelihood of spontaneous vaginal delivery (OR 1.46 [1.18 to 1.86]), reduced motor block (Bromage score >0; OR 0.32 [0.18 to 0.54]) and reduced duration of second stage of labour (weighted mean difference -13.02 min [-21.54 to -4.77]). Compared with low, ultra-low concentration local anaesthetic had similar estimates for duration of second stage of labour (weighted mean difference -1.92 min [-14.35 to 10.20]); spontaneous vaginal delivery (OR 1.07 [0.75 to 1.56]; assisted vaginal delivery (OR 1.35 [0.75 to 2.26]); caesarean section (OR 0.76 [0.49 to 1.22]); pain (scale 1-100, weighted mean difference -5.44 [-16.75 to 5.93]); and maternal satisfaction. Although a lower risk of an Apgar score < 7 at 1 min (OR 0.43 [0.15 to 0.79]) was reported for ultra-low compared with low concentration, this was not sustained at 5 min (OR 0.12 [0.00 to 2.10]). Ultra-low concentration local anaesthetic for labour epidural achieves similar or better maternal and neonatal outcomes as low and high concentration, but with reduced local anaesthetic consumption.

Keywords: Bayesian; epidural; labour analgesia; local anaesthetic; maternal outcomes; meta-analysis; obstetric outcomes.

Figure 1

PRISMA flow chart for study selection.

Figure 2

Network comparisons for assisted vaginal delivery. Edges are weighted according to the number of studies included in each comparison. Six compared ultra‐low concentration with low concentration, 27 compared ultra‐low concentration with high concentration and 5 compared low concentration with high concentration. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 3

Box and whisker plot for (a) binary and (b) continuous outcomes. Low concentration is the reference concentration to which high and ultra‐low concentrations are compared. The box represents the IQR and the whiskers represent the 95% credible intervals. The credible intervals for hypotension have been truncated to fit (see Table 1 for upper limits of credible intervals). AVD, assisted vaginal delivery; SVD, spontaneous vaginal delivery.