[Alkalization of bupivacaine in the combination fentanyl-bupivacaine in epidural obstetrical analgesia].

A randomized double blind study was carried out to determine whether alkalization of a 0.25% bupivacaine solution in a fentanyl-bupivacaine mixture hastened the onset, and increased the duration and quality, of extradural analgesia during labour. The study included 120 women with uncomplicated full-term gestation. Prior to the extradural injection, 0.1 ml of either 8.4% sodium bicarbonate or normal saline was randomly added to 20 ml of 0.25% bupivacaine. The patients were given 75 micrograms fentanyl with 12 ml of either alkalized or unaltered bupivacaine. Data for analysis were obtained in 106 parturients (bicarbonate group n = 54; control group n = 52). The pH of alkalized and unaltered bupivacaine were 7.07 +/- 0.01 and 5.56 +/- 0.01 respectively. There were no statistically significant differences between the bicarbonate and control groups with regard to the speed of onset of analgesia (7.08 +/- 0.7 min vs. 6.78 +/- 0.6 min), its duration (123.6 +/- 10.7 min vs. 113 +/- 6.6 min), and the number of cases of inadequate pain relief (6 and 3 respectively). The rate of maternal adverse effects, and neonatal status, were similar in both groups. It can be concluded that alkalizing a 0.25% bupivacaine solution in a fentanyl-bupivacaine mixture for epidural analgesia in labour has no clinical value.