Epidural mepivacaine for cesarean section: effects of a pH-adjusted solution.

STUDY OBJECTIVE

To determine the clinical effects of the alkalinization of 2% mepivacaine with epinephrine used for epidural block during cesarean section.

DESIGN

Randomized, double-blind, placebo-controlled (standard commercial preparation of 2% mepivacaine with epinephrine) study.

SETTING

Inpatient obstetric department at a general hospital.

PATIENTS

Seventy patients scheduled for elective cesarean section under epidural anesthesia.

INTERVENTIONS

Two groups of 35 patients each receiving either the standard commercial preparation of mepivacaine or the pH-adjusted solution (prepared with the addition of 0.1 meq/ml of sodium bicarbonate to the standard commercial solution).

MEASUREMENTS AND MAIN RESULTS

Measurements of sensory (pinprick) and motor (Bromage's criteria) block were taken at 1- to 2-minute intervals beginning after the completion of the epidural injection. Increasing the pH of the mepivacaine resulted in a significant shortening of the time of analgesia onset (9.3 minutes compared with 16.01 minutes, p less than 0.01) and of peak effect (11.1 minutes compared with 21.2 minutes, p less than 0.01). The alkalinization did not affect duration of the block, intensity of motor block, or mean dose of local anesthetic used.

CONCLUSION

The alkalinization allowed the surgery to proceed more rapidly, significantly decreasing the time interval between epidural block and delivery of the infant.