title: Quantitative testing of sympathetic function with laser Doppler flowmetry.
abstract: OBJECTIVE
  The objective of this study was to develop an indirect technique for evaluating dynamic changes in sympathetic function in humans.
  
  
  METHODS
  We used laser Doppler to monitor sympathetic mediated vasoconstrictive responses (VRs) produced by 3 different provocative stimuli: 4-second inspiratory gasp (IG), ice-water immersion (Ice), and a spring-loaded pin prick (Pin). Skin perfusion on the thenar eminence was continuously monitored in 10 normal subjects (aged 25 to 36 years) using laser Doppler. Ten trials of the 3 stimuli were presented to each subject at 1-minute intervals. We determined the VR, the percent decrease in perfusion produced by each stimulus, and the 2 standard deviation variation in perfusion.
  
  
  RESULTS
  No subject found the IG maneuver uncomfortable. In contrast, the Pin and Ice stimuli were reported to be uncomfortable by 8 and 10 subjects, respectively. Five subjects found Pin and Ice stimuli overtly painful. Vasoconstrictive response was 54.1 +/- 2.3% (mean +/- SEM) with IG, 49.2 +/- 2.0% with Ice, and 24.0 +/- 1.8% with Pin. Baseline variation was approximately 15% in all trials.
  
  
  CONCLUSIONS
  Inspiratory gasp vasoconstrictive response (IGVR) is a sensitive indirect technique for evaluating sympathetic efferent function. We observed that the magnitude of the VR elicited by the IG stimuli was similar to that induced by cold water. Unlike the VR induced by Pin or Ice, IGVR is not dependent on noxious input via somatic afferents; therefore, it can be used in patients with diseases that produce a peripheral neuropathy, such as diabetes mellitus. Present uses of this technique and speculation on future uses are presented.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Johns Hopkins Hospital, Baltimore, MD.
authors.forename: M A
authors.initials: MA
authors.lastname: Valley
authors.forename: D L
authors.initials: DL
authors.lastname: Bourke
authors.forename: A M
authors.initials: AM
authors.lastname: McKenzie
authors.forename: S N
authors.initials: SN
authors.lastname: Raja
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008297:Male; D012016:Reference Values; D013564:Sympathetic Nervous System / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology*