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Clonidine decreases vasoconstriction and shivering thresholds, without affecting the sweating threshold.
Can J Anaesth. 1997 Jun; 44(6):636-42.CJ

Abstract

PURPOSE

This study was conducted to test the hypothesis that clonidine produces a dose-dependent increase in the sweating threshold and dose-dependent decreases in vasoconstriction and shivering thresholds.

METHODS

Six healthy subjects (two female) were studied on four days after taking clonidine in oral doses of either 0 (control), 3, 6 or 9 micrograms.kg-1. The order followed a balanced design in a double-blind fashion. Oesophageal temperature and mean skin temperature (from 12 sites) were measured. Subjects were seated in 37 degrees C water which was gradually warmed until sweating occurred (sweat rate increased above 50 g.m-2.h-1). The water was then cooled gradually until thresholds for vasoconstriction (onset of sustained decrease in fingertip blood flow) and shivering (sustained elevation in metabolism) were determined. Thresholds were then referred to as the core temperature, adjusted to a designated mean skin temperature of 33 degrees C.

RESULTS

High dose clonidine similarly decreased the adjusted core temperature thresholds for vasoconstriction by 1.16 +/- 0.30 degrees C and for shivering by 1.63 +/- 0.23 degrees C (P < 0.01). The dose response effects were linear for both cold responses with vasoconstriction and shivering thresholds decreasing by 0.13 +/- 0.05 and 0.19 +/- 0.09 degree C.microgram-1 respectively (P < 0.0001). The sweating threshold was unaffected by clonidine, however the interthreshold range between sweating and vasoconstriction thresholds increased from control (0.19 +/- 0.48 degree C) to high dose clonidine (1.31 +/- 0.54 degrees C).

CONCLUSION

The decreases in core temperature thresholds for cold responses and increased interthreshold range are consistent with the effects of several anaesthetic agents and opioids and is indicative of central thermoregulatory inhibition.

Authors+Show Affiliations

Laboratory for Exercise and Environmental Medicine, Health, Leisure and Human Performance Research Institute, Winnipeg, Manitoba, Canada.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Clinical Trial
Controlled Clinical Trial
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

9187784

Citation

Nicolaou, G, et al. "Clonidine Decreases Vasoconstriction and Shivering Thresholds, Without Affecting the Sweating Threshold." Canadian Journal of Anaesthesia = Journal Canadien D'anesthesie, vol. 44, no. 6, 1997, pp. 636-42.
Nicolaou G, Chen AA, Johnston CE, et al. Clonidine decreases vasoconstriction and shivering thresholds, without affecting the sweating threshold. Can J Anaesth. 1997;44(6):636-42.
Nicolaou, G., Chen, A. A., Johnston, C. E., Kenny, G. P., Bristow, G. K., & Giesbrecht, G. G. (1997). Clonidine decreases vasoconstriction and shivering thresholds, without affecting the sweating threshold. Canadian Journal of Anaesthesia = Journal Canadien D'anesthesie, 44(6), 636-42.
Nicolaou G, et al. Clonidine Decreases Vasoconstriction and Shivering Thresholds, Without Affecting the Sweating Threshold. Can J Anaesth. 1997;44(6):636-42. PubMed PMID: 9187784.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Clonidine decreases vasoconstriction and shivering thresholds, without affecting the sweating threshold. AU - Nicolaou,G, AU - Chen,A A, AU - Johnston,C E, AU - Kenny,G P, AU - Bristow,G K, AU - Giesbrecht,G G, PY - 1997/6/1/pubmed PY - 1997/6/1/medline PY - 1997/6/1/entrez SP - 636 EP - 42 JF - Canadian journal of anaesthesia = Journal canadien d'anesthesie JO - Can J Anaesth VL - 44 IS - 6 N2 - PURPOSE: This study was conducted to test the hypothesis that clonidine produces a dose-dependent increase in the sweating threshold and dose-dependent decreases in vasoconstriction and shivering thresholds. METHODS: Six healthy subjects (two female) were studied on four days after taking clonidine in oral doses of either 0 (control), 3, 6 or 9 micrograms.kg-1. The order followed a balanced design in a double-blind fashion. Oesophageal temperature and mean skin temperature (from 12 sites) were measured. Subjects were seated in 37 degrees C water which was gradually warmed until sweating occurred (sweat rate increased above 50 g.m-2.h-1). The water was then cooled gradually until thresholds for vasoconstriction (onset of sustained decrease in fingertip blood flow) and shivering (sustained elevation in metabolism) were determined. Thresholds were then referred to as the core temperature, adjusted to a designated mean skin temperature of 33 degrees C. RESULTS: High dose clonidine similarly decreased the adjusted core temperature thresholds for vasoconstriction by 1.16 +/- 0.30 degrees C and for shivering by 1.63 +/- 0.23 degrees C (P < 0.01). The dose response effects were linear for both cold responses with vasoconstriction and shivering thresholds decreasing by 0.13 +/- 0.05 and 0.19 +/- 0.09 degree C.microgram-1 respectively (P < 0.0001). The sweating threshold was unaffected by clonidine, however the interthreshold range between sweating and vasoconstriction thresholds increased from control (0.19 +/- 0.48 degree C) to high dose clonidine (1.31 +/- 0.54 degrees C). CONCLUSION: The decreases in core temperature thresholds for cold responses and increased interthreshold range are consistent with the effects of several anaesthetic agents and opioids and is indicative of central thermoregulatory inhibition. SN - 0832-610X UR - https://www.unboundmedicine.com/medline/citation/9187784/Clonidine_decreases_vasoconstriction_and_shivering_thresholds_without_affecting_the_sweating_threshold_ L2 - https://doi.org/10.1007/BF03015448 DB - PRIME DP - Unbound Medicine ER -