The influence of pH-adjusted 2-chloroprocaine on the quality and duration of subsequent epidural bupivacaine analgesia during labor: a randomized, double-blind study.

A randomized, double-blind study was performed to determine whether pH-adjustment of 2-chloroprocaine hastens the onset of epidural analgesia, and improves the quality and duration of subsequent epidural bupivacaine analgesia during labor. One milliliter of either 8.4% sodium bicarbonate or normal saline was added to a 30-ml vial of 2% 2-chloroprocaine. At 0, 5, and 7 min, each patient received 2, 5, and 3 ml of 2-chloroprocaine, respectively. At 22 min, any patient who did not yet have satisfactory analgesia received an additional 5 ml of 2-chloroprocaine. At 35, and, again, at 36 min, each patient received 5 ml of 0.25% bupivacaine. The median onset of 2-chloroprocaine analgesia was slightly more rapid in the bicarbonate group than in the saline-control group (12 versus 14 min, P less than .05). Two of 31 women in the bicarbonate group, versus 10 of 31 women in the saline-control group, required an additional 5 ml of 2-chloroprocaine at 22 min to achieve satisfactory analgesia (P = .01). There was no significant difference between groups in median duration of subsequent bupivacaine analgesia (60 min in each group) or mean (+/- SD) dosage of bupivacaine during the first stage of labor (64 +/- 43 versus 72 +/- 57 mg). Also, there was no significant difference between groups in pain scores over time.(ABSTRACT TRUNCATED AT 250 WORDS)