title: Limited upper thoracic epidural block and splanchnic perfusion in dogs.
abstract: Epidural blockade leads to a sympathetic block in affected segments and an increase of sympathetic out-flow from various unblocked segments. A limited upper thoracic epidural block (LUTEB) is used during coronary artery surgery affecting the cardiac sympathetic fibers cephalad to the fifth thoracic segment. This block does not extend to the sympathetic fibers innervating the gastrointestinal organs. A LUTEB may lead to an increase of sympathetic activity in the unaffected splanchnic sympathetic segments and the decrease in splanchnic blood flow may contribute to gastrointestinal ischemia after cardiac surgery. We tested the hypothesis that a LUTEB decreases splanchnic perfusion in anesthetized dogs. Thirteen dogs were chronically instrumented with aortic and left atrial catheters, which were used for pressure measurement, as well as injection and withdrawal of reference samples. Thoracic epidural catheters were placed under general anesthesia the day before the experiment. Splanchnic blood flow was determined by using colored microspheres. Induction of a LUTEB did not change general hemodynamics in awake dogs. Propofol anesthesia induced an increase in heart rate that was abolished after LUTEB. LUTEB also decreased mean arterial pressure during propofol anesthesia. We conclude that thoracic epidural anesthesia had no effect on splanchnic blood flow. In propofol anesthetized animals, liver blood flow was increased compared with awake animals; however, it did not change after induction of LUTEB.
  
  
  CONCLUSIONS
  A sympathetic block in certain segments leads to increased sympathetic output in unblocked segments. For an upper thoracic epidural block, this might lead to impaired splanchnic perfusion. In awake and propofol-anesthetized, chronically instrumented dogs, however, a limited upper thoracic epidural blockade had no compromising effect on gastrointestinal perfusion.
authors.affiliation: Klinik und Poliklinik für Anästhesiologie und operative Intensivmedizin der Westfälischen Wilhelms-Universität Münster, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Meissner
authors.forename: T P
authors.initials: TP
authors.lastname: Weber
authors.forename: H
authors.initials: H
authors.lastname: Van Aken
authors.forename: N
authors.initials: N
authors.lastname: Rolf
mesh_terms: D000767:Anesthesia, Epidural / Q000009:adverse effects* / Q000379:methods*; D018686:Anesthetics, Intravenous / Q000494:pharmacology; D000818:Animals; D016275:Atrial Function / Q000187:drug effects / Q000502:physiology; D001340:Autonomic Nerve Block / Q000009:adverse effects; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D004285:Dogs; D005260:Female; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D008102:Liver Circulation / Q000187:drug effects / Q000502:physiology; D008297:Male; D015742:Propofol / Q000494:pharmacology; D013152:Splanchnic Circulation / Q000187:drug effects / Q000502:physiology*; D013909:Thorax
chemical_list: D018686:Anesthetics, Intravenous; D015742:Propofol