title: Possible utility of contrast-enhanced ultrasonography for detecting spread of local anesthetic in nerve block.
abstract: OBJECTIVE
  This study demonstrated the effects of perfluorobutane (Sonazoid®) with contrast-enhanced ultrasonography (CEUS) to identify the spread of local anesthetics in ultrasound-guided nerve block.
  
  
  METHODS
  This study consists of simulation, cadaveric, and animal studies. In a simulation study, 1% lidocaine with 10- to 1000-fold diluted Sonazoid®, a US-specific contrast agent to diagnose hepatic and breast cancers (0.5 mL), was injected into a resin-based phantom to determine the optimal concentration for ultrasound-guided peripheral nerve block. The enhanced area was measured by direct observation and ultrasonography (US). In the cadaver study, ultrasound-guided sciatic nerve block was performed at the popliteal fossa in the 9 extremities, and 5 mL of the optimally diluted Sonazoid®defined in the simulation study with X-ray contrast medium and blue dye was injected. Longitudinal spread of the solution was measured by CEUS, X-ray imaging and anatomical dissection. In the animal study, the optimally diluted Sonazoid®was injected around the sciatic nerve of rats (n = 6), and neuronal function and toxicity were evaluated by behavioral and histological estimation.
  
  
  RESULTS
  The simulation study proved that 100-fold diluted Sonazoid®was the optimal concentration. In the cadaver study, CEUS and anatomical dissection (r = 0.90, P = 0.0020) or radiography (r = 0.84, P = 0.0072) showed high agreement and correlation with the longitudinal spread. CEUS clearly showed a fine intraneuronal injection image compared to the usual B-mode imaging. The animal study suggested no adverse effects by co-administration of lidocaine and Sonazoid®.
  
  
  CONCLUSIONS
  CEUS with 100-fold diluted Sonazoid®could identify the spread of local anesthetic as well as radiography and anatomical dissection, and distinguish between intra- and extraneuronal injections without neurodegeneration.
authors.affiliation: Department of Anesthesiology, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Sasaki
authors.affiliation: Department of Anesthesiology and Perioperative Medicine, Tohoku University School of Medicine, Seiryo-cho 1-1, Aoba-ku, Sendai, Miyagi, 980-8575, Japan. yamauchi@med.tohoku.ac.jp.
authors.forename: Masanori
authors.identifier: http://orcid.org/0000-0001-8708-6852
authors.initials: M
authors.lastname: Yamauchi
authors.affiliation: Department of Anatomy, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Ninomiya
authors.affiliation: Department of Anatomy, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Haruyuki
authors.initials: H
authors.lastname: Tatsumi
authors.affiliation: Department of Anesthesiology, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Michiaki
authors.initials: M
authors.lastname: Yamakage
mesh_terms: D000779:Anesthetics, Local / Q000008:administration & dosage*; D000818:Animals; D003287:Contrast Media / Q000008:administration & dosage; D005290:Ferric Compounds / Q000008:administration & dosage; D005466:Fluorocarbons / Q000008:administration & dosage; D006801:Humans; D007267:Injections; D007501:Iron / Q000008:administration & dosage; D008012:Lidocaine / Q000008:administration & dosage*; D008297:Male; D009407:Nerve Block / Q000379:methods*; D010087:Oxides / Q000008:administration & dosage; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000000981:diagnostic imaging; D018084:Ultrasonography, Interventional / Q000379:methods*
chemical_list: D000779:Anesthetics, Local; D003287:Contrast Media; D005290:Ferric Compounds; D005466:Fluorocarbons; D010087:Oxides; C069727:Sonazoid; D008012:Lidocaine; D007501:Iron; C108042:perfluorobutane
keywords: Cadaver; Contrast medium; Nerve block; Perfluorobutane; Ultrasonography