title: The effect of altering skin-surface cooling speeds on vasoconstriction and shivering thresholds.
abstract: BACKGROUND
  Both core and skin temperatures contribute to steady-state thermoregulatory control. Dynamic thermoregulatory responses trigger aggressive defenses against rapid thermal perturbations. These responses potentially complicate interpretation of thermoregulatory studies and could slow induction of therapeutic hypothermia. We thus tested the hypothesis that rapid external skin-cooling triggers vasoconstriction and shivering at higher mean skin temperatures than slow or moderate rates of skin cooling.
  
  
  METHODS
  Eleven healthy volunteers were cooled at 3 skin-cooling rates using forced air or/and conductive cooling in random order. One day volunteers received slow (≈2°C/h) skin cooling, and on another day, they received both medium (≈4°C/h) and fast (≈6°C/h) skin cooling. An endovascular heat-exchanging catheter maintained core temperature. Fingertip blood flow ≤0.25 mL/min defined onset of vasoconstriction; sustained ≥25% increase in oxygen consumption defined onset of shivering. Results were evaluated with repeated-measures analysis of variance, with P < 0.05 representing statistical significance.
  
  
  RESULTS
  Volunteers were 25 ± 5 years of age (mean ± SD), 175 ± 7 cm tall, and weighed 63 ± 10 kg. Core temperature remained constant (≈37°C) throughout each study day. At vasoconstriction, mean skin temperatures were 33.2°C (95% confidence interval [CI]: 32.0°C, 34.4°C), 33.5°C (95% CI: 32.3°C, 34.7°C), and 33.0°C (95% CI: 31.4°C, 34.6°C) at slow, medium, and fast skin-cooling rates, respectively. Mean skin temperatures at shivering were also comparable: 31.4°C (95% CI: 30.3°C, 32.5°C), 31.5°C (95% CI: 30.2°C, 32.8°C), and 30.7°C (95% CI: 28.9°C, 32.5°C), respectively.
  
  
  CONCLUSIONS
  Onset of vasoconstriction and shivering occurred at similar mean skin temperatures with all 3 cooling rates. Aggressive surface cooling can thus be used in thermoregulatory studies and for induction of therapeutic hypothermia without provoking dynamic thermoregulatory defenses.
authors.affiliation: Department of Anesthesia, University of Bern, Bern, Switzerland.
authors.forename: Yoshie
authors.initials: Y
authors.lastname: Taniguchi
authors.forename: Rainer
authors.initials: R
authors.lastname: Lenhardt
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Sessler
authors.forename: Andrea
authors.initials: A
authors.lastname: Kurz
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001783:Blood Flow Velocity; D005385:Fingers / Q000098:blood supply*; D006801:Humans; D007036:Hypothermia, Induced; D010101:Oxygen Consumption; D012039:Regional Blood Flow; D012768:Shivering; D012881:Skin Temperature; D013557:Switzerland; D013997:Time Factors; D014661:Vasoconstriction; D055815:Young Adult