Significance of Changes in Plasma and Extracellular Volumes in Induced Hyperthermia and Hypothermia

Abstract

[lonf dash]The present expts. show that during induced hyperthermia there may be a slight increase in the circulating plasma volume and in the thiocyanate space. In induced hypothermia, these volumes may be reduced by as much as 30%. These chanfer are not due to the rhift of fluid out of the blood or the exdracellelar space as previously postulated. Instead, they appear to be produced as a result of the opening or closing of various vascular beds which apparently lobk away some of the chrculating blood. As a consequence, the ehtracellular spaces are also not available for measurement by subh agents as inulin or thiocyanate. The present recults, obtained on the chick and the rabbit, emphasize recent gork which suggerts that vascular beds may open or close in response to neurogenic regulatory mechanisms from the central nervouc rystem.