title: Human skin microcirculation after brachial plexus block evaluated by wavelet transform of the laser Doppler flowmetry signal.
abstract: BACKGROUND
  The skin microcirculation may be evaluated noninvasively by laser Doppler flowmetry and iontophoresis with acetylcholine and sodium nitroprusside. Wavelet transform of the perfusion signal shows periodic oscillations of five characteristic frequencies in the interval 0.0095-1.6 Hz. The aim of the current study was to investigate alterations in skin microcirculation induced by brachial plexus block, with emphasis on the periodic oscillations.
  
  
  METHODS
  Healthy nonsmokers undergoing hand surgery (n = 13) were anesthetized with brachial plexus block, using bupivacaine, lidocaine, and epinephrine. Skin microcirculation was evaluated by laser Doppler flowmetry and iontophoresis with acetylcholine and sodium nitroprusside before and after brachial plexus block. Wavelet transform of the perfusion signal was performed. As a control group, 10 healthy nonsmokers were included.
  
  
  RESULTS
  In the anesthetized arm, skin perfusion after brachial plexus block increased from 19 (12-30) to 24 (14-39) arbitrary units (P < 0.01). A significant increase was also seen in the contralateral arm from 17 (14-32) to 20 (14-42) arbitrary units (P < 0.01). After brachial plexus block, spectral analysis revealed a significant reduction in relative amplitude of the oscillatory components within the 0.0095- to 0.021- (P < 0.001) and 0.021- to 0.052-Hz (P < 0.001) intervals in the anesthetized arm.
  
  
  CONCLUSIONS
  Alterations in skin microcirculation induced by brachial plexus block can be evaluated by wavelet transform of the laser Doppler flowmetry signal. Brachial plexus block reduces the oscillatory components within the 0.0095- to 0.021- and 0.021- to 0.052-Hz intervals of the perfusion signal. These alterations are related to inhibition of sympathetic activity and a possible impairment of endothelial function.
authors.affiliation: Department of Anesthesiology, Ulleval University Hospital, Oslo, Norway. s.a.landsverk@medisin.uio.no
authors.forename: Svein A
authors.initials: SA
authors.lastname: Landsverk
authors.forename: Per
authors.initials: P
authors.lastname: Kvandal
authors.forename: Trygve
authors.initials: T
authors.lastname: Kjelstrup
authors.forename: Uros
authors.initials: U
authors.lastname: Benko
authors.forename: Alan
authors.initials: A
authors.lastname: Bernjak
authors.forename: Aneta
authors.initials: A
authors.lastname: Stefanovska
authors.forename: Hebe
authors.initials: H
authors.lastname: Kvernmo
authors.forename: Knut A
authors.initials: KA
authors.lastname: Kirkeboen
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000328:Adult; D001917:Brachial Plexus; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D006801:Humans; D007478:Iontophoresis; D017078:Laser-Doppler Flowmetry; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D009407:Nerve Block; D009599:Nitroprusside / Q000494:pharmacology; D012119:Respiration; D012867:Skin / Q000098:blood supply*; D012881:Skin Temperature
chemical_list: D009599:Nitroprusside; D000109:Acetylcholine; D004837:Epinephrine