Percentage of parturients with dense (grade 2 or 3) motor block following institution of epidural anesthesia and for 5 hours subsequently in those receiving:
CEI: Continuous Epidural Infusion of plain bupivacaine.
PCEA-B: PCEA with plain bupivacaine.
PCEA-BF: PCEA with bupivacaine/fentanyl solution.
PCEA-BFE: PCEA with bupivacaine/Epinephrine/Fentanyl solution.

Each point represents the mean of 8-22 patients. Group PCEA-BFE differs from the others by 2 way ANOVA. *P <0.05 cf 0 time point. Data from Lysak S et al. Anesthesiology 1990:72 p 47 Figure 4.

Note the increase in motor block both with the increasing duration of epidural analgesia and in association with the use of epinephrine-containing solutions.