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

Abstract

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.