An Experimental and Theoretical Investigation of Hypothermia in Dogs

Abstract

A technique for post surgical rewarming from clinical hypothermia, which utilizes a thoracic flush with heated saline solution, has been investigated experimentally and theoretically. The rewarming technique was used in conjunction with surface cooling for eighteen separate experiments using mongrel dogs, with the thermal response of the animals determined from thermocouple measurements at twelve strategic locations. Utilizing these measurements, temperature histories were established for the animals, from which representative cooling and rewarming rates have been determined. The rectal temperature was found to provide a suitable clinical reference temperature for monitoring the level of hypothermia, and the rewarming rates (from 10 to 22° C/hr) compare favorably with those obtained by other investigators using surface and extracorporeal rewarming methods. Reasonable agreement was obtained between the measured temperature histories and theoretical predictions obtained using a simple lumped parameter heat transfer model.

An experimental and theoretical study of heat transfer and temperature control in the dog

“…In the experiment, if the dog's temperature reached a critical temperature, the environ ment was changed, thus changing the response of the dog. Mauck et al (1977) provide a model of a dog during hypothermia.…”

“…In the Mauck et al (1977) (Mauck et al, 1977) The results of their model are shown in Figure 7. A fairly good reproduction of the experimental results is obtained.…”

“…Figure 7. Comparison of Mauck model and experimental results (Mauck et al, 1977) Human Thermoregulatory Models…”

“…That is, the dog only inspires the amount of air necessary to meet its metabolic require ments . 9 Mauck et al, (1977) gives a value of 6.77 w/m^min C as the convective heat transfer coefficient from the skin of a dog to air. This value is assumed to be constant throughout the experiment.…”

“…This mass was chosen because it best represents the data obtained in the experimental portion of the experiment and because data are available on the volume and surface areas for segments of a dog of this mass. Mauck et al (1975) give the data from which the following table of compartment sizes is obtained. From these values of the radii and lengths of the various model compartments, the effective distance for conduction can be calculated by dividing the area of the mid-point concentric surface by the dif ference in radii of the centers of mass (assuming homogeneous regions)…”