88016
document
Clonidine increases the sweating threshold , but does not reduce the gain of sweating . We tested the hypothesis that clonidine produces a dose-dependent increase in the sweating threshold but does not reduce the gain of sweating . Six healthy male volunteers were evaluated , each on three separate days in random order . In one , saline was administered ; in another , a 2-micrograms/kg bolus of clonidine was followed by an infusion at 2 micrograms.kg-1.h-1 , and on a third day , a 4-micrograms/kg bolus was followed by an infusion at 4 micrograms.kg-1.h-1 . Core temperature was measured at the tympanic membrane and mean skin temperature was determined from four sites . A chest sweating rate of 40 g.m-2.h-1 was considered significant . The core temperature triggering sweating , adjusted to a designated mean skin temperature of 34 degrees C , identified the threshold for this response . Gain was defined by the adjusted core temperature increase required to augment sweating from 100 to 300 g.m-2.h-1 . degree C-1 . Plasma clonidine concentrations were 0.8 +/- 0.1 and 1.6 +/- 0.2 ng/mL on the small- and large-dose days , respectively . Clonidine administration increased the sweating threshold approximately 0.4 degree C ( P < 0.05 ) , but the increase was comparable at each dose . The gain of sweating was approximately 0.2 degree C and was not influenced by clonidine administration . The thermoregulatory effects of clonidine thus resemble those of volatile anesthetics , opioids , and propofol . These data suggest that the antishivering effect of clonidine results from central thermoregulatory inhibition rather than a specific peripheral action on thermogenic muscular activity . Unlike other sedatives and anesthetics , the concentration-dependence of clonidine demonstrates a ceiling beyond which the administration of an additional drug fails to enhance the effect , suggesting that the thermoregulatory effect of clonidine may be limited , even at high plasma concentrations . The gain of sweating was well preserved indicating that this response remains effective in the presence of sedatives and anesthetics .
88017
Intervention_Pharmacological
Clonidine
88018
Intervention_Pharmacological
clonidine
88019
Intervention_Control
saline
88020
Intervention_Pharmacological
clonidine
88021
Outcome_Physical
sweating threshold
88022
Outcome_Physical
gain of sweating .
88023
Outcome_Physical
increase in the sweating threshold
88024
Outcome_Physical
reduce the gain of sweating .
88025
Outcome_Physical
Core temperature
88026
Outcome_Physical
mean skin temperature
88027
Outcome_Physical
chest sweating rate
88028
Outcome_Physical
sweating
88029
Outcome_Physical
core temperature
88030
Outcome_Physical
Plasma clonidine concentrations
88031
Outcome_Physical
gain of sweating
88032
Outcome_Physical
thermoregulatory effects
88033
Participant_Condition
sweating threshold