The epidural "top-up": predictors of increase of sensory blockade.

Background: Extension of sensory blockade after an epidural top-up in combined spinal epidural (CSE) anesthesia is partly attributed to compression of the dural sac by the injected volume. This study investigated whether a volume effect plays a significant role when administering an epidural top-up after an initial epidural loading dose and assessed the predictive value of different factors with respect to the increase in sensory blockade.

Methods: After an epidural loading dose of 75 mg ropivacaine, 0.