title: Thoracic epidural analgesia with low concentration of bupivacaine induces thoracic and lumbar sympathetic block: a randomized, double-blind clinical trial.
abstract: BACKGROUND
  Clinical benefits of thoracic epidural anesthesia (TEA) are partly ascribed to thoracic sympathetic block. However, data regarding sympathetic activity during TEA are scarce and contradictory. This prospective, randomized, double-blind study evaluated the segmental propagation of sympathetic block after low-concentration, high-volume TEA using digital thermography.
  
  
  METHODS
  Twenty-four patients were included in the study. Thoracic epidural catheters were placed at a median insertion level of T8-T9. Patients were accommodated for 20 min to the room temperature of 23 degrees +/- 0.3 degrees C. Skin temperature was recorded by digital thermography. After baseline measurement of heart rate, arterial pressure, and core body and skin temperature, 10 ml saline (control group) or 10 ml bupivacaine, 0.25% (TEA group), respectively, was administered epidurally. Five minutes (t5) and 20 min (t20) after baseline measurements, hemodynamic parameters and core body temperature were again measured, and sensory block was identified by loss of cold-warm discrimination. In the thumb, the toe, and each thoracic dermatome, difference from baseline temperature was calculated at t5 and t20. Data were analyzed by Mann-Whitney U test.
  
  
  RESULTS
  Baseline characteristics did not differ among groups. Median spread of sensory block at t20 was T5-L5. At both t5 and t20, skin temperature decreased more in the control group than in the TEA group in all thoracic dermatomes (P < 0.05). Toe temperature increased in the TEA group compared with the control group (P < 0.05), whereas thumb temperature remained unchanged.
  
  
  CONCLUSIONS
  TEA with 10 ml bupivacaine, 0.25%, induced thoracic and lumbar sympathetic block that precedes and exceeds sensory block. Caudal limit of sympathetic block could not be demonstrated in this study.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, University Hospital Muenster, Albert Schweitzer Strasse33, 48149 Muenster, Germany. freiseh@uni-muenster.de
authors.forename: Hendrik
authors.initials: H
authors.lastname: Freise
authors.forename: Andreas
authors.initials: A
authors.lastname: Meissner
authors.forename: Stefan
authors.initials: S
authors.lastname: Lauer
authors.forename: Björn
authors.initials: B
authors.lastname: Ellger
authors.forename: Robert
authors.initials: R
authors.lastname: Radke
authors.forename: Mathias
authors.initials: M
authors.lastname: Bruewer
authors.forename: Gerd
authors.initials: G
authors.lastname: Brodner
authors.forename: Hugo K
authors.initials: HK
authors.lastname: Van Aken
authors.forename: Andreas W
authors.initials: AW
authors.lastname: Sielenkämper
authors.forename: Lars G
authors.initials: LG
authors.lastname: Fischer
mesh_terms: D000328:Adult; D000368:Aged; D015360:Analgesia, Epidural; D001340:Autonomic Nerve Block / Q000379:methods*; D002045:Bupivacaine / Q000008:administration & dosage*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008161:Lumbosacral Region / Q000502:physiology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012881:Skin Temperature / Q000187:drug effects / Q000502:physiology; D013909:Thorax / Q000187:drug effects* / Q000502:physiology
chemical_list: D002045:Bupivacaine