Effects of Carbon Dioxide, Epinephrine and Ilidar on Skin, Blood and Rectal Temperatures of Unanesthetized Dogs Exposed to Extreme Cold

¹ From the Division of Veterinary Physiology and Pharmacology, University of Minnesota, St. Paul, Minnesota

Polyethylene cannulae were surgically placed in the pulmonary artery and in the posterior vena cava at a point where the hepatic veins enter (referred to as ‘hepatic vein’). Thermistors mounted in polyethylene tubing, were passed through these cannulae and the temperature changes of blood, skin (thorax, forearm, paw) and rectum were recorded photographically. The effects of carbon dioxide, epinephrine and Ilidar were superimposed on extreme cold while continuously recording blood, rectal and skin temperatures. Carbon dioxide inhalation was associated with a fall in blood and rectal temperatures and marked diminution of shivering. Little effect on skin temperatures was noted. It was thought that the decrease in metabolism contributed to the fall in ‘core’ temperature. Epinephrine, given intravenously in doses of 2.5 µg/kg was associated with an immediate cessation in shivering which persisted for 1–3 minutes. Blood and rectal temperatures fell slightly; skin temperatures showed little change. The intravenous administration of Ilidar in doses of 4.0 mg/kg was associated with rather marked rises in blood and rectal temperatures which were additive to those resulting from exposure to cold. Skin temperatures were only slightly affected. Apparently the doses of Ilidar were too small to block cutaneous vasoconstriction induced by sympathetic impulses reaching the cutaneous vessels. Vasodilation in the viscera could result in shunting blood away from the skin and in this way increase internal temperatures.