scholarly journals Clonidine decreases vasoconstriction and shivering thresholds, without affecting the sweating threshold

1997 ◽  
Vol 44 (6) ◽  
pp. 636-642 ◽  
Author(s):  
George Nicolaou ◽  
A. Andrew Chen ◽  
Chad E. Johnston ◽  
Glen P. Kenny ◽  
Gerald K. Bristow ◽  
...  
Keyword(s):  
Sweating Threshold

DOSE-RESPONSE FOR THERMOREGULATORY SWEATING THRESHOLD AND GAIN DURING ISOFLURANE ANESTHESIA

1991 ◽  
Vol 75 (3) ◽  
pp. A194-A194
Author(s):  
D Washington ◽  
D I Sessler ◽  
M Prager ◽  
J McGuire ◽  
B Merrifield ◽  
...  
Keyword(s):  
Dose Response ◽  
Isoflurane Anesthesia ◽  
Sweating Threshold

Clonidine Increases the Sweating Threshold, but Does Not Reduce the Gain of Sweating

1996 ◽  
Vol 83 (4) ◽  
pp. 844-848 ◽  
Author(s):  
Laurent Delaunay ◽  
Thierry Herail ◽  
Daniel I. Sessler ◽  
Andre Lienhart ◽  
Francis Bonnet
Keyword(s):  
Sweating Threshold

Influence of training on sweating responses during submaximal exercise in horses

2000 ◽  
Vol 89 (6) ◽  
pp. 2463-2471 ◽  
Author(s):  
L. J. McCutcheon ◽  
R. J. Geor
Keyword(s):  
Relative Humidity ◽  
Core Temperature ◽  
Heat Dissipation ◽  
Fold Increase ◽  
Moderate Intensity ◽  
Dry Conditions ◽  
Fluid Losses ◽  
Sweating Threshold ◽  
Intensity Training ◽  
Cool Conditions

Sweating responses were examined in five horses during a standardized exercise test (SET) in hot conditions (32–34°C, 45–55% relative humidity) during 8 wk of exercise training (5 days/wk) in moderate conditions (19–21°C, 45–55% relative humidity). SETs consisting of 7 km at 50% maximal O2 consumption, determined 1 wk before training day (TD) 0, were completed on a treadmill set at a 6° incline on TD0, 14, 28, 42, and 56. Mean maximal O2consumption, measured 2 days before each SET, increased 19% [TD0 to 42: 135 ± 5 (SE) to 161 ± 4 ml · kg−1 · min−1]. Peak sweating rate (SR) during exercise increased on TD14, 28, 42, and 56 compared with TD0, whereas SRs and sweat losses in recovery decreased by TD28. By TD56, end-exercise rectal and pulmonary artery temperature decreased by 0.9 ± 0.1 and 1.2 ± 0.1°C, respectively, and mean change in body mass during the SET decreased by 23% (TD0: 10.1 ± 0.9; TD56: 7.7 ± 0.3 kg). Sweat Na+concentration during exercise decreased, whereas sweat K+concentration increased, and values for Cl− concentration in sweat were unchanged. Moderate-intensity training in cool conditions resulted in a 1.6-fold increase in sweating sensitivity evident by 4 wk and a 0.7 ± 0.1°C decrease in sweating threshold after 8 wk during exercise in hot, dry conditions. Altered sweating responses contributed to improved heat dissipation during exercise and a lower end-exercise core temperature. Despite higher SRs for a given core temperature during exercise, decreases in recovery SRs result in an overall reduction in sweat fluid losses but no change in total sweat ion losses after training.

Reduced sweating threshold during exercise-induced hyperthermia

1995 ◽  
Vol 430 (5) ◽  
pp. 606-611 ◽  
Author(s):  
Michael Lopez ◽  
Daniel I. Sessler ◽  
Kristin Walter ◽  
Thomas Emerick ◽  
Anitha Ayyalapu
Keyword(s):  
Induced Hyperthermia ◽  
Exercise Induced ◽  
Sweating Threshold

A simple and valid method to determine thermoregulatory sweating threshold and sensitivity

2009 ◽  
Vol 107 (1) ◽  
pp. 69-75 ◽  
Author(s):  
Samuel N. Cheuvront ◽  
Shawn E. Bearden ◽  
Robert W. Kenefick ◽  
Brett R. Ely ◽  
David W. DeGroot ◽  
...  
Keyword(s):  
Temperature Sensor ◽  
Sweat Rate ◽  
Dew Point ◽  
Threshold Temperature ◽  
Data Sets ◽  
Empirical Methods ◽  
Dew Point Temperature ◽  
The Relationship ◽  
Sweating Threshold

Sweating threshold temperature and sweating sensitivity responses are measured to evaluate thermoregulatory control. However, analytic approaches vary, and no standardized methodology has been validated. This study validated a simple and standardized method, segmented linear regression (SReg), for determination of sweating threshold temperature and sensitivity. Archived data were extracted for analysis from studies in which local arm sweat rate (ṁsw; ventilated dew-point temperature sensor) and esophageal temperature (Tes) were measured under a variety of conditions. The relationship ṁsw/Tes from 16 experiments was analyzed by seven experienced raters (Rater), using a variety of empirical methods, and compared against SReg for the determination of sweating threshold temperature and sweating sensitivity values. Individual interrater differences ( n = 324 comparisons) and differences between Rater and SReg ( n = 110 comparisons) were evaluated within the context of biologically important limits of magnitude (LOM) via a modified Bland-Altman approach. The average Rater and SReg outputs for threshold temperature and sensitivity were compared ( n = 16) using inferential statistics. Rater employed a very diverse set of criteria to determine the sweating threshold temperature and sweating sensitivity for the 16 data sets, but interrater differences were within the LOM for 95% (threshold) and 73% (sensitivity) of observations, respectively. Differences between mean Rater and SReg were within the LOM 90% (threshold) and 83% (sensitivity) of the time, respectively. Rater and SReg were not different by conventional t-test ( P > 0.05). SReg provides a simple, valid, and standardized way to determine sweating threshold temperature and sweating sensitivity values for thermoregulatory studies.

Effect of hyperosmolality on control of blood flow and sweating

1984 ◽  
Vol 57 (6) ◽  
pp. 1688-1695 ◽  
Author(s):  
S. M. Fortney ◽  
C. B. Wenger ◽  
J. R. Bove ◽  
E. R. Nadel
Keyword(s):  
Blood Flow ◽  
Maximal Exercise ◽  
Forearm Blood Flow ◽  
Fluid Restriction ◽  
O2 Consumption ◽  
Rest Interval ◽  
Ambient Conditions ◽  
Exercise Tests ◽  
Sweating Threshold ◽  
Humidity Environment

To study the effect of hyperosmolality on thermoregulatory responses, five men [average maximal O2 consumption (VO2 max) = 48 ml X kg-1 X min-1] cycled at 65-75% VO2max for up to 30 min in a 30 degrees C, 40% relative humidity environment under three conditions. First, control tests (C) were performed where preexercise plasma volume (PV) and osmolality (Osm) averaged 3,800 ml and 282 mosmol X kg-1, respectively. Second, exercise tests (D) were performed following dehydration induced by fluid restriction and mild exercise (30% VO2max) in hot (40 degrees C) ambient conditions. Each subject then rested in cool surroundings 1 h before performing the exercise test. Preexercise PV and Osm averaged 3,606 ml and 293 mosmol X kg-1, respectively. Third, exercise tests (I) were performed following dehydration, but during the 1-h rest interval, 3% saline was infused so that PV was restored to 3,826 ml and Osm averaged 294 mosmol X kg-1 prior to exercise. During D, esophageal temperatures (Tes) were significantly higher than C, an avg 0.56 degrees C after 20 min exercise due to a 0.22 degrees C increase in Tes threshold for vasodilation, a 39% reduction in slope of the forearm blood flow (BF)-Tes relationship, a 32% average reduction in maximal exercise BF, and a 0.22 degrees C increase in Tes sweating threshold. During I, responses were similar to D, except the BF-Tes slope and the maximum BF were not significantly different from C. Thus hyperosmolality modifies thermoregulation by elevating thresholds for both vasodilation and sweating even without decreases in PV.

Factors determining the sweating threshold

1971 ◽  
Vol 15 (2-4) ◽  
pp. 286-291
Author(s):  
G. W. Crockford ◽  
K. P. Foster ◽  
J. Haspineall
Keyword(s):  
Sweating Threshold

Propofol Linearly Reduces the Vasoconstriction and Shivering Thresholds 

1995 ◽  
Vol 82 (5) ◽  
pp. 1169-1180 ◽  
Author(s):  
Takashi Matsukawa ◽  
Andrea Kurz ◽  
Daniel I. Sessler ◽  
Andrew R. Bjorksten ◽  
Benjamin Merrifield ◽  
...  
Keyword(s):  
Skin Temperature ◽  
Core Temperature ◽  
Response Curves ◽  
Target Concentration ◽  
The Core ◽  
Temperature Thresholds ◽  
Cutaneous Temperature ◽  
Response Thresholds ◽  
Temperature Manipulation ◽  
Sweating Threshold

Background Skin temperature is best kept constant when determining response thresholds because both skin and core temperatures contribute to thermoregulatory control. In practice, however, it is difficult to evaluate both warm and cold thresholds while maintaining constant cutaneous temperature. A recent study shows that vasoconstriction and shivering thresholds are a linear function of skin and core temperatures, with skin contributing 20 +/- 6% and 19 +/- 8%, respectively. (Skin temperature has long been known to contribute approximately 10% to the control of sweating). Using these relations, we were able to experimentally manipulate both skin and core temperatures, subsequently compensate for the changes in skin temperature, and finally report the results in terms of calculated core-temperature thresholds at a single-designated skin temperature. Methods Five volunteers were each studied on 4 days: (1) control; (2) a target blood propofol concentration of 2 micrograms/ml; (3) a target concentration of 4 micrograms/ml; and (4) a target concentration of 8 micrograms/ml. On each day, we increased skin and core temperatures sufficiently to provoke sweating. Skin and core temperatures were subsequently reduced to elicit peripheral vasoconstriction and shivering. We mathematically compensated for changes in skin temperature by using the established linear cutaneous contributions to the control of sweating (10%) and to vasoconstriction and shivering (20%). From these calculated core-temperature thresholds (at a designated skin temperature of 35.7 degrees C), the propofol concentration-response curves for the sweating, vasoconstriction, and shivering thresholds were analyzed using linear regression. We validated this new method by comparing the concentration-dependent effects of propofol with those obtained previously with an established model. Results The concentration-response slopes for sweating and vasoconstriction were virtually identical to those reported previously. Propofol significantly decreased the core temperature triggering vasoconstriction (slope = -0.6 +/- 0.1 degrees C.micrograms-1.ml-1; r2 = 0.98 +/- 0.02) and shivering (slope = -0.7 +/- 0.1 degrees C.micrograms -1.ml-1; r2 = 0.95 +/- 0.05). In contrast, increasing the blood propofol concentration increased the sweating threshold only slightly (slope = 0.1 +/- 0.1 degrees C.micrograms -1.ml-1; r2 = 0.46 +/- 0.39). Conclusions Advantages of this new model include its being nearly noninvasive and requiring relatively little core-temperature manipulation. Propofol only slightly alters the sweating threshold, but markedly reduces the vasoconstriction and shivering thresholds. Reductions in the shivering and vasoconstriction thresholds are similar; that is, the vasoconstriction-to-shivering range increases only slightly during anesthesia.

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