A Systematic Review and Meta-Analysis of Randomized Controlled Trials of Labor Epidural Analgesia Using Moderately High Concentrations of Plain Local Anesthetics versus Low Concentrations of Local Anesthetics with Opioids

PURPOSE: Compared to low concentrations of local anesthetics with opioids for labor epidural analgesia, very high concentrations of local anesthetics are associated with an increased risk of assisted vaginal delivery. We aimed to investigate if moderately high concentrations of plain local anesthetics are also associated with this risk. METHODS: We searched for published randomized controlled trials that compared moderately high concentrations of plain local anesthetics (>0.1% but ≤0.125% bupivacaine, >0.1% but ≤0.125% levobupivacaine, or >0.17% but ≤0.2% ropivacaine) to low concentrations of local anesthetics (≤0.1% bupivacaine, ≤0.1% levobupivacaine, or ≤0.17% ropivacaine) with opioids for labor analgesia. Meta-analyses were performed to compare the risk of assisted vaginal delivery and other perinatal outcomes between these two groups. RESULTS: We identified nine randomized controlled trials with a total of 1334 participants. Meta-analysis of these nine trials showed no differences in the risks of assisted vaginal delivery (odds ratio [OR] = 1.18; 95% confidence interval [CI], 0.93–1.49) or Cesarean delivery (OR = 0.96; 95% CI, 0.71–1.29) between the two groups. The incidence of motor block was higher in the group of moderately high concentrations (OR = 4.05; 95% CI, 2.19–7.48), while the incidence of pruritus was lower (OR = 0.07; 95% CI, 0.03–0.16). CONCLUSION: This systematic review and meta-analysis suggests that the current evidence is inadequate to support that moderately high concentrations of plain local anesthetics increase the risk of assisted vaginal delivery compared to low concentrations of local anesthetics with opioids.