Discomfort associated with regional anesthetic placement in obstetrics: does alkalinization help?

Lidocaine is commonly used prior to intravenous catheter insertion as well as before instituting a regional anesthetic[ but it often causes a burning discomfort during injection. We undertook this study to determine if the addition of bicarbonate to lidocaine would decrease the discomfort associated with the initiation of regional anesthesia in obstetrics. Forty patients who were scheduled for elective cesarean section or who were in active labor were selected. Lidocaine was prepared before infiltration using 9 ml of preservative-free 1% lidocaine with either 1 ml of preservative-free normal saline or 1 ml of sodium bicarbonate (1 mEq.ml(-1)). A skin wheal was raised with 0.5 ml of the solution; the remainder (1.5 ml) was injected into the deep tissues. Pain was assessed using visual analog scales on three occasions, immediately after lidocaine placement, following introducer needle insertion (in the spinal group) or following epidural needle insertion (in the epidural group), and following the successful placement of the local anesthetic (in the spinal group) or the epidural catheter (in the epidural group). There was no difference in the visual analog scale scores at any of the assessment periods. We found no benefit from adding sodium bicarbonate to lidocaine used for infiltration before needle placement when initiating an obstetrical regional anesthetic.