title: Magnetic resonance imaging analysis of the spread of local anesthetic solution after ultrasound-guided lateral thoracic paravertebral blockade: a volunteer study.
abstract: BACKGROUND
  This study was designed to examine the spread of local anesthetic (LA) via magnetic resonance imaging after a standardized ultrasound-guided thoracic paravertebral blockade.
  
  
  METHODS
  Ten volunteers were enrolled in the study. We performed ultrasound-guided single-shot paravertebral blocks with 20 ml mepivacaine 1% at the thoracic six level at both sides on two consecutive days. After each paravertebral blockade, a magnetic resonance imaging investigation was performed to investigate the three-dimensional spread of the LA. In addition, sensory spread of blockade was evaluated via pinprick testing.
  
  
  RESULTS
  The median (interquartile range) cranial and caudal distribution of the LA relative to the thoracic six puncture level was 1.0 (2.5) and 3.0 (0.75) [=4.0 vertebral levels] for the left and 0.5 (1.0) and 3.0 (0.75) [=3.5 vertebral levels] for the right side. Accordingly, the LA distributed more caudally than cranially. The median (interquartile range) number of sensory dermatomes which were affected by the thoracic paravertebral blockade was 9.8 (6.5) for the left and 10.7 (8.8) for the right side. The sensory distribution of thoracic paravertebral blockade was significantly larger compared with the spread of LA.
  
  
  CONCLUSIONS
  Although the spread of LA was reproducible, the anesthetic effect was unpredictable, even with a standardized ultrasound-guided technique in volunteers. While it can be assumed that approximately 4 vertebral levels are covered by 20 ml LA, the somatic distribution of the thoracic paravertebral blockade remains unpredictable. In a significant percentage, the LA distributes into the epidural space, prevertebral, or to the contralateral side.
authors: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria. peter.marhofer@meduniwien.ac.at
authors: Daniela
authors: D
authors: Marhofer
authors: Peter
authors: P
authors: Marhofer
authors: Stephan C
authors: SC
authors: Kettner
authors: Edith
authors: E
authors: Fleischmann
authors: Daniela
authors: D
authors: Prayer
authors: Melanie
authors: M
authors: Schernthaner
authors: Edith
authors: E
authors: Lackner
authors: Harald
authors: H
authors: Willschke
authors: Pascal
authors: P
authors: Schwetz
authors: Markus
authors: M
authors: Zeitlinger
mesh_terms: D000328:Adult; D000779:Anesthetics, Local / Q000009:adverse effects / Q000493:pharmacokinetics*; D001794:Blood Pressure / Q000187:drug effects; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009407:Nerve Block / Q000009:adverse effects / Q000379:methods*; D012307:Risk Factors; D013904:Thoracic Vertebrae / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D018084:Ultrasonography, Interventional / Q000379:methods*; D055815:Young Adult
chemical_list: D000779:Anesthetics, Local