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The effect of epidural local anesthetic concentration on labor outcomes: A meta-analysis
Abstract Number: MA-03
Abstract Type: Meta Analysis/Review of the Literature
Despite the publication of multiple randomized controlled trials (RCTs) and meta-analyses the effect of epidural analgesia on labor outcomes remains controversial. This may be because all epidurals are not the same. The effect of an epidural on labor may depend upon the concentration of local anesthetic solution run through it. We performed a meta-analysis of available RCTs to assess the effect of varying epidural local anesthetic concentration on instrument-assisted and cesarean delivery rates.
This study qualified for exemption from the Oregon Health and Science University IRB. Systematic literature searches of the PubMed, EMBASE, and Cochrane Central databases were conducted in May 2013 for relevant RCTs using terms related to epidural analgesia and labor outcomes. Search terms were: [Epidural OR Obstetrical Analgesia OR Obstetrical Anesthesia OR Patient-Controlled Analgesia] AND [Obstetric Labor OR Second Stage Labor OR labor Pain OR Pregnancy]. Studies were included if they compared epidural solutions administered in the same manner (continuous infusion, PCEA, provider bolus, etc.) containing two different local anesthetic concentrations. Data on pertinent study characteristics and relevant outcomes were recorded and analyzed for each accepted article. A random effects model was used. All data analysis was completed with RevMan version 5.1.0 (The Cochrane Collaboration, 2011).
The search yielded 24 studies that met all inclusion criteria. There were a total of 2053 subjects in the high concentration group and 2485 subjects in the low concentration group. Most of the studies used bupivacaine in the epidural solution. The high concentration solutions varied between 0.1% and 0.5%. The low concentration solutions varied between 0.031% and 0.25%. One study compared 0.1% ropivacaine to 0.15% ropivacaine. Using a higher concentration local anesthetic epidural solution was associated with a significant increase in cesarean delivery rate (Odds Ratio [OR]=1.19; 95% confidence interval [CI]: 1.01 to 1.41, p = 0.04) and instrument-assisted delivery rate (OR=1.31; 95% CI: 1.13 to 1.53, p < 0.001). Using a higher concentration local anesthetic solution was associated with an increased risk of motor block (OR=4.76; 95% CI: 2.84 to 7.99, p < 0.001), but was not associated with any increase in odds of maternal hypotension (OR=0.85; 95% CI: 0.51 to 1.42, p = 0.55).
Our meta-analysis examining the effect of varying local anesthetic concentration on labor outcomes found an association between higher concentrations of local anesthetic and the need for cesarean and instrument-assisted vaginal delivery. In this meta-analysis, the difference in local anesthetic concentration between the two study arms was enough to affect the incidence of motor block.