Dexmedetomidine does not alter the sweating threshold, but comparably and linearly decreases the vasoconstriction and shivering thresholds.
BACKGROUND
Clonidine decreases the vasoconstriction and shivering thresholds. It thus seems likely that the alpha2 agonist dexmedetomidine will also impair control of body temperature. Accordingly, the authors evaluated the dose-dependent effects of dexmedetomidine on the sweating, vasoconstriction, and shivering thresholds. They also measured the effects of dexmedetomidine on heart rate, blood pressures, and plasma catecholamine concentrations.


METHODS
Nine male volunteers participated in this randomized, double-blind, cross-over protocol. The study drug was administered by computer-controlled infusion, targeting plasma dexmedetomidine concentrations of 0.0, 0.3, and 0.6 ng/ml. Each day, skin and core temperatures were increased to provoke sweating and then subsequently reduced to elicit vasoconstriction and shivering. Core-temperature thresholds were computed using established linear cutaneous contributions to control of sweating, vasoconstriction, and shivering. The dose-dependent effects of dexmedetomidine on thermoregulatory response thresholds were then determined using linear regression. Heart rate, arterial blood pressures, and plasma catecholamine concentrations were determined at baseline and at each threshold.


RESULTS
Neither dexmedetomidine concentration increased the sweating threshold from control values. In contrast, dexmedetomidine administration reduced the vasoconstriction threshold by 1.61 +/- 0.80 degrees C x ng(-1) x ml (mean +/- SD) and the shivering threshold by 2.40 +/- 0.90 degrees C x ng(-1) x ml. Hemodynamic responses and catecholamine concentrations were reduced from baseline values, but they did not differ at the two tested dexmedetomidine doses.


CONCLUSIONS
Dexmedetomidine markedly increased the range of temperatures not triggering thermoregulatory defenses. The drug is thus likely to promote hypothermia in a typical hospital environment; it is also likely to prove an effective treatment for shivering.
Talke
P
P
Department of Anesthesia, University of California, San Francisco 94143-0648, USA. pekka_talke@quickmail.ucsf.edu
Tayefeh
F
F
Sessler
D I
DI
Jeffrey
R
R
Noursalehi
M
M
Richardson
C
C
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000328:Adult; D001833:Body Temperature Regulation / Q000187:drug effects; D004311:Double-Blind Method; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D008297:Male; D020926:Medetomidine; D012768:Shivering / Q000187:drug effects*; D013546:Sweating / Q000187:drug effects*; D014661:Vasoconstriction / Q000187:drug effects*
D000316:Adrenergic alpha-Agonists; D007093:Imidazoles; D020926:Medetomidine