Cross-sectional areas of deep/core veins are smaller at lower core body temperatures

Abstract

The cardiovascular system plays a crucial role in thermoregulation. Deep core veins, due to their large size and role in returning blood to the heart, are an important part of this system. The response of veins to increasing core temperature has not been adequately studied in vivo. Our objective was to noninvasively quantify in C57BL/6 mice the response of artery‐vein pairs to increases in body temperature. Adult male mice were anesthetized and underwent magnetic resonance imaging. Data were acquired from three colocalized vessel pairs (the neck [carotid/jugular], torso [aorta/inferior vena cava (IVC)], periphery [femoral artery/vein]) at core temperatures of 35, 36, 37, and 38°C. Cross‐sectional area increased with increasing temperature for all vessels, excluding the carotid. Average area of the jugular, aorta, femoral artery, and vein linearly increased with temperature (0.10, 0.017, 0.017, and 0.027 mm2/°C, respectively; P < 0.05). On average, the IVC has the largest venous response for area (18.2%/°C, vs. jugular 9.0 and femoral 10.9%/°C). Increases in core temperature from 35 to 38 °C resulted in an increase in contact length between the aorta/IVC of 29.3% (P = 0.007) and between the femoral artery/vein of 28.0% (P = 0.03). Previously unidentified increases in the IVC area due to increasing core temperature are biologically important because they may affect conductive and convective heat transfer. Vascular response to temperature varied based on location and vessel type. Leveraging noninvasive methodology to quantify vascular responses to temperature could be combined with bioheat modeling to improve understanding of thermoregulation.

Assessing structural and functional response of murine vasculature to acute β-adrenergic stimulation in vivo during hypothermic and hyperthermic conditions

“…Comparing these recently published results with data presented here, one can begin to estimate the seemingly opposing factors of changes in core temperature and dobutamine administration on core arteries. For example, Crouch et al quantified an ~4%, 1%, and 6% increase in area for the carotid artery, infrarenal aorta, and femoral artery, respectively, when core temperature is increased from 37 to 38 °C [20]. Here, for hyperthermia with dobutamine relative to hyperthermia alone we show a ~20%, 7%, and 5% decrease in area for the same vessels, respectively.…”

“…Dobutamine-induced decreases in average cross-sectional area of the core arteries during normothermic conditions are consistent with redistribution of blood to the skin/periphery due to dobutamine’s vasodilatory effects [9,22]. Conversely, cross-sectional area of the core arteries increase with increasing temperature, paralleling hyperthermia-induced vasodilation known to occur in the skin/periphery [19,20]. Comparing these recently published results with data presented here, one can begin to estimate the seemingly opposing factors of changes in core temperature and dobutamine administration on core arteries.…”

“…To improve parameterization and validation of mathematical and computational models [18], recent work has used magnetic resonance imaging (MRI) to quantify geometric (cross-sectional area) and functional (Green-Lagrange circumferential strain) changes in core arteries and veins due to increases in core temperature [19,20]. Previous work by Crouch et al showed that under hypothermic conditions (35 °C) the average area was significantly smaller in the infrarenal aorta and femoral artery by −12% and −72%, respectively, and larger for hyperthermic conditions (38 °C) by 1.3 and 6.0%, respectively, compared to normothermic conditions (37 °C) [20].…”

“…To improve parameterization and validation of mathematical and computational models [18], recent work has used magnetic resonance imaging (MRI) to quantify geometric (cross-sectional area) and functional (Green-Lagrange circumferential strain) changes in core arteries and veins due to increases in core temperature [19,20]. Previous work by Crouch et al showed that under hypothermic conditions (35 °C) the average area was significantly smaller in the infrarenal aorta and femoral artery by −12% and −72%, respectively, and larger for hyperthermic conditions (38 °C) by 1.3 and 6.0%, respectively, compared to normothermic conditions (37 °C) [20]. While cross-sectional area tended to increase with temperature, with larger changes occurring inferiorly, previous work in well-controlled and nearly identical conditions, Castle et al showed that cross-sectional area at normothermic conditions decreased with the administration of dobutamine for the carotid, suprarenal and infrarenal aorta, and iliac artery by −19%, −16%, −14%, and −12%, respectively, with larger changes occurring superiorly in the body [22].…”

“…For either increases in core temperature or dobutamine administration, the end-diastolic/minimum areas experienced larger changes than the peak-systolic/maximum areas, resulting in changes in maximum cyclic strain. Temperature’s effect on strain varied by location with a general overall decrease in strain from 35 to 38 °C [19,20], whereas dobutamine caused an increase in maximum cyclic strain for all vessels [22]. Combining these two cardiac stressors is of interest because of the differential response of core vasculature to changing temperature or administration of dobutamine alone.…”