Venous Blood Flow in the Dog Leg Following Cold Injury

Abstract

In an attempt to determine the nature of the circulatory changes which occur in tissues injured by exposure to cold, the rate of venous outflow was studied in the dog's hind leg exposed to freezing temperatures. Before exposure to cold, control flow rates were determined, and changes in flow were measured following the injection of vasoactive drugs. Measurements were continued during a 30-minute immersion of the leg in an alcohol-solid carbon dioxide bath (app. –30°C), and then for several hours after the leg had been removed and thawed. Control blood flow rates were found to vary considerably from animal to animal (20 cc/min. to 90 cc/min.) but varied little in each individual. During exposure to cold, in most of the experiments, the legs froze: flow decreased almost to zero, and the temperature in the leg fell well below 0°C. In some experiments, however, the legs did not freeze: flow remained high throughout exposure, and tissue temperature remained above 0°C. In response to the injection of vasoactive drugs, the control venous outflow showed: a) a decrease after intravenous epinephrine; b) a decrease after intra-arterial epinephrine into the experimental leg; c) a transient increase after intra-arterial acetylcholine into the experimental leg. After exposure to cold, the legs which did not freeze still showed these reactions. However, in the legs which were frozen the reactions to intra-arterially injected drugs were very much diminished, and the flow was increased instead of decreased when epinephrine was intravenously administered.