title: The epidural "top-up": predictors of increase of sensory blockade.
abstract: 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, 0.75%, 30 patients were randomly assigned to one of three groups. After the maximum level of sensory blockade (MLSB) had been established, patients received either an epidural top-up with 10 ml ropivacaine, 0.75% (group 1, n = 10) or saline (group 2, n = 10), or no epidural top-up (group 3, n = 10). Subsequently, sensory blockade was assessed at 5-min intervals for a further 30 min by a blinded observer.
  
  
  RESULTS
  The MLSB increased significantly in the patients receiving an epidural top-up with ropivacaine but not in the patients receiving normal saline. Sensory block extension was inversely related to the number of segments blocked at the time of the epidural top-up, and female gender was associated with a smaller increase in MLSB.
  
  
  CONCLUSIONS
  When using epidural ropivacaine, the extension of sensory blockade after administering an epidural top-up is caused by a local anesthetic effect and not by a volume effect. Under the conditions of this study, predictors of the increase in sensory blockade are the presence of ropivacaine in the top-up injectate, the number of segments blocked at the time of epidural top-up, and gender.
authors.affiliation: Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Michal
authors.initials: M
authors.lastname: Leeda
authors.forename: Rudolf
authors.initials: R
authors.lastname: Stienstra
authors.forename: M Sesmu
authors.initials: MS
authors.lastname: Arbous
authors.forename: Maarten J M
authors.initials: MJ
authors.lastname: Verschure
authors.forename: Albert
authors.initials: A
authors.lastname: Dahan
authors.forename: Bernadette Th
authors.initials: BT
authors.lastname: Veering
authors.forename: Jack W
authors.initials: JW
authors.lastname: van Kleef
authors.forename: Anton G L
authors.initials: AG
authors.lastname: Burm
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000577:Amides / Q000134:cerebrospinal fluid; D000767:Anesthesia, Epidural / Q000379:methods*; D000775:Anesthesia, Spinal / Q000379:methods*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D000077212:Ropivacaine; D012677:Sensation
chemical_list: D000577:Amides; D000077212:Ropivacaine