Effect of standard diluted epinephrine infusion on epidural anesthesia in labor

Epinephrine is used with local anesthetics to prolong the duration of epidural analgesia and decrease the peak plasma concentrations of local anesthetics. However, the duration of labor may be prolonged because epinephrine reduces uterine activity. We designed a prospective, randomized, and doubleblind study to examine the effects of epinephrine infusion on the quality of analgesia and plasma concentration of local anesthetic, as well as the effect on the uteroplacental circulation, duration of the first or second stage of labor, and fetal outcome.

Twenty-four parturients received continuous epidural bupivacaine 0.125% (8 mL/h) combined either with epinephrine (40 microg/h) (n = 12) or without epinephrine (n = 12) for analgesia during labor. If patients requested additional analgesia, a bolus of 1% or 1.5% lidocaine (6 to 10 mL) was given.

Only the plain bupivacaine group required additional lidocaine. However, epinephrine infusion prolonged the median (range) duration of the second stages of labor: 69 (21 to 231) minutes with epinephrine group versus 31 (8 to 99) minutes without epinephrine group (P < .05), and decreased pH in umbilical artery at the time of delivery. Epinephrine infusion did not change the uterine and umbilical blood flow, which were determined as the resistance indices. Changes in the fetal heart rate and Apgar score were also comparable. Epinephrine significantly reduced the umbilical venous to maternal arterial bupivacaine concentration (P < .05).

A standard diluted epinephrine infusion (40 microg/h) into epidural space decreased anesthetic requirements. The possibility of the prolonged duration of labor remains a problem.