0.125% bupivacaine for obstetric analgesia?

A prospective trial was designed to assess the effectiveness of three different concentrations of bupivacaine (Marcain) for use in obstetric epidural analgesia. The purpose of the study was to see if reduction of the concentration of bupivacaine to 0.125% would reduce the total dose of the drug given without reducing the efficiency of the epidural block. The concentrations studies were 0.125%, 0.25% and 0.375%. The trial was limited to fit primiparous patients at term with singleton pregnancies and vertex presentation. Patients with intercurrent medical disease or with toxaemia were excluded. A total of ninety-three patients were studied, and once admitted to the trial they were randomly allocated to one of the three concentrations. In general the results of the trial show that 0.125% bupivacaine had a significantly higher failure rate than either of the other two concentrations, but in those cases where 0.125% was effective and achieved total pain relief there was a significant reduction in the amount of the drug used.