Effects of hypothermia on the mechanical behavior of rabbit femoral arteries.

Abstract

The need to better understand the effects of non-physiological temperatures on arterial wall behavior is becoming more important because of the increased clinical use of hypothermal and hyperthermal treatments. The present study was performed to examine the effects of temperature on the mechanical behavior of femoral arteries excised from rabbits. Among 17, 27, 37, and 42°C, there were no significant differences in their diameter, stiffness, and P-D relations under the physiologically normal, control condition, although the arterial diameter was slightly smaller at 42°C than at the other three temperatures. Under the SMC-activated condition, on the other hand, we observed significant effects of temperature. For example, arterial diameter at 100mmHg was significantly larger at 17 and 27°C and smaller at 42°C compared with 37°C. Arterial stiffness at 40mmHg were significantly smaller at 17 and larger at 42°C than at 37°C, while the stiffness at 160mmHg were significantly larger at 17°C than at 37°C; however, there were no significant differences in the stiffness at 100mmHg among the four temperatures. Arterial contraction induced by SMC-activation was significantly different between 37°C and the other three temperatures; both of the maximum diameter response and diameter response at 100mmHg were significantly smaller at 17 and 27°C and larger at 42°C compared with 37°C. These results indicate that in the hypothermic range under the control condition, arteries are dilated when cooled, while they are constricted when heated. On the other hand, arterial response to SMC activation is significantly affected by the alterations of temperature. These results indicate that in the hypothermic range under the control condition, arteries are dilated when cooled, while they are constricted when heated. On the other hand, arterial response to the activation of vascular smooth muscle cells is significantly affected by the alteration of temperature. As the mechanical behavior of arterial wall is significantly influenced by temperature, this should be considered in the development of therapeutic methods and techniques for cardiovascular diseases.