Key result
Mean unilateral common carotid blood flow in dogs increased from 6.2 ml/min/kg at 25 degrees C to 16.8 ml/min/kg at 45 degrees C, in parallel with increasing respiratory water loss.
Absolute Event Rate: 16.8% vs 6.2%
Carotid flow increases during canine heat exposure warrant no clinical translation; leaves open mechanistic parallels for human thermoregulation.
Common carotid blood flow (CCBF) and respiratory water loss (RWL) were measured in dogs resting at ambient temperatures between 25 and 50 degrees C, during hypothalamic heating, and during light and heavy exercise at ambient temperatures of 25 and 35 degrees C. In resting dogs, CCBF varied with the level of RWL. Elevations in CCBF and RWL occurred within seconds of each other during bursts of panting. Mean unilateral CCBF increased from 6.2 ml . min-1 . kg-1 at 25 degrees C to 16.8 ml . min-1 . kg-1 at 45 degrees C, in parallel with increasing RWL. Hypothalamic heating elicited simultaneous elevations in CCBF and RWL, and the level of CCBF was strongly correlated with the hypothalamic temperature. Both CCBF and RWL increased rapidly at the onset of exercise and continued to rise during a 15-min run. Highest rates of blood flow and evaporation occurred during heavy exercise at 35 degrees C. It is concluded that the rate of blood flow through the common carotid arteries in the dog is related to the thermoregulatory needs of the animal, and most of the increased flow occurring during heat stress is destined for evaporative surfaces of the nose, mouth, and tongue.
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Baker et al. (1982) studied this question. Thermoregulatory stress (ambient temperature changes, hypothalamic heating, exercise) vs. Resting at 25 degrees C was evaluated on Common carotid blood flow (CCBF). Mean unilateral common carotid blood flow in dogs increased from 6.2 ml/min/kg at 25 degrees C to 16.8 ml/min/kg at 45 degrees C, in parallel with increasing respiratory water loss.
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