title: The effects of general anesthesia on human skin microcirculation evaluated by wavelet transform.
abstract: BACKGROUND
  Time-frequency analysis of the laser Doppler flowmetry signal, using wavelet transform, shows periodic oscillations at five characteristic frequencies related to the heart (0.6-2 Hz), respiration (0.15-0.6 Hz), myogenic activity in the vessel wall (0.052-0.15 Hz), sympathetic activity (0.021-0.052 Hz), and very slow oscillations (0.0095-0.021), which can be modulated by the endothelium-dependent vasodilator acetylcholine. We hypothesized that wavelet transform of laser Doppler flowmetry signals could detect changes in the microcirculation induced by general anesthesia, such as alterations in vasomotion and sympathetic activity.
  
  
  METHODS
  Eleven patients undergoing faciomaxillary surgery were included. Skin microcirculation was measured on the lower forearm with laser Doppler flowmetry and iontophoresis with acetylcholine and sodium nitroprusside before and during general anesthesia with propofol, fentanyl, and midazolam. The laser Doppler flowmetry signals were analyzed using wavelet transform.
  
  
  RESULTS
  There were significant reductions in spectral amplitudes in the 0.0095-0.021 (P < 0.01), the 0.021-0.052 (P < 0.001), and the 0.052-0.15 Hz frequency interval (P < 0.01) and a significant increase in the 0.15-0.6 Hz frequency interval. General anesthesia had no effect on the difference between acetylcholine and sodium nitroprusside on relative amplitudes in the 0.0095-0.021 Hz frequency interval (P < 0.001).
  
  
  CONCLUSIONS
  General anesthesia reduces the oscillatory components of the perfusion signal related to sympathetic, myogenic activity and the component modulated by the endothelium. However, the iontophoretic data did not reveal a specific effect on the endothelium. The increase in the 0.15-0.6 Hz interval is related to the effect of mechanical ventilation.
authors: Department of Anesthesiology, Ulleval University Hospital, Oslo, Norway. s.a.landsverk@medisin.uio.no
authors: Svein Aslak
authors: SA
authors: Landsverk
authors: Per
authors: P
authors: Kvandal
authors: Alan
authors: A
authors: Bernjak
authors: Aneta
authors: A
authors: Stefanovska
authors: Knut A
authors: KA
authors: Kirkeboen
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000293:Adolescent; D000328:Adult; D000768:Anesthesia, General; D001794:Blood Pressure; D005260:Female; D005542:Forearm; D006801:Humans; D007478:Iontophoresis; D017078:Laser-Doppler Flowmetry; D008297:Male; D008833:Microcirculation; D009599:Nitroprusside / Q000494:pharmacology; D012119:Respiration; D012867:Skin / Q000098:blood supply*; D012881:Skin Temperature; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D014665:Vasodilator Agents; D009599:Nitroprusside; D000109:Acetylcholine