title: Assessment of blood flow changes in human skin by microdialysis urea clearance.
abstract: OBJECTIVE
  The aim of this study was to evaluate the urea clearance technique for the measurement of drug-induced blood flow changes in human skin and compare it to two non-invasive techniques: polarization light spectroscopy and laser Doppler perfusion imaging.
  
  
  METHODS
  Fifteen microdialysis catheters were placed intracutaneously on the volar aspect of the forearms of healthy human subjects and were perfused with nitroglycerine, noradrenaline, and again nitroglycerine to induce local tissue hyperemia, hypoperfusion, and hyperemia, respectively.
  
  
  RESULTS
  Urea clearance, but not the other techniques, detected the changes in blood flow during changes in flow. The last hyperemic response was detected by all three methods.
  
  
  CONCLUSIONS
  Urea clearance can be used as a relatively simple method to estimate blood flow changes during microdialysis of vasoactive substances, in particular when the tissue is preconditioned in order to enhance the contrast between baseline and the responses to the provocations. Our results support that, in the model described, urea clearance was superior to the optical methods as it detected both the increases and decrease in blood flow, and the returns to baseline between these periods.
authors.affiliation: Department of Plastic Surgery, Hand Surgery, and Burns, Linköping University Hospital, Linköping University, Linköping, Sweden. simon.farnebo@lio.se
authors.forename: Simon
authors.initials: S
authors.lastname: Farnebo
authors.forename: Erik K
authors.initials: EK
authors.lastname: Zettersten
authors.forename: Anders
authors.initials: A
authors.lastname: Samuelsson
authors.forename: Erik
authors.initials: E
authors.lastname: Tesselaar
authors.forename: Folke
authors.initials: F
authors.lastname: Sjöberg
mesh_terms: D006801:Humans; D006940:Hyperemia / Q000139:chemically induced; D008722:Methods; D017551:Microdialysis / Q000379:methods*; D005996:Nitroglycerin; D009638:Norepinephrine / Q000494:pharmacology; D012039:Regional Blood Flow / Q000187:drug effects; D012867:Skin / Q000098:blood supply*; D014508:Urea / Q000493:pharmacokinetics*
chemical_list: D014508:Urea; D005996:Nitroglycerin; D009638:Norepinephrine