The Responses of Arterial Stiffness Parameter Beta-Derived Index of the Aorta and Illiac-Femoral Artery to Acute Hypovolemia in Rabbits

Abstract

Introduction: Acute hemorrhage decreases blood pressure (BP) and sometimes causes hypovolemic shock. At this time, peripheral arteries are supposed to contract and increase peripheral vascular resistance to raise BP. However, there have not been an adequate index of a degree of arterial stiffness. We assessed changes in arterial stiffness during rapid bleeding using new BP-independent vascular indices, aBeta and ifBeta, determined by applying the cardio-ankle vascular index (CAVI) theory to the elastic (aorta) and muscular (common iliac-femoral) arteries, respectively in rabbits. Methods: Eleven Japanese white male rabbits were fixed at supine under pentobarbital anesthesia. Fifteen percent of the total blood volume was depleted at a rate of 2 mL/kg/min for 6 min; 15 min later, the withdrawn blood was re-transfused at the same rate. Pressure waves at the origin of the aorta (oA), distal end of the abdominal aorta, distal end of the left common iliac artery, and flow waves at oA were measured simultaneously. Beta was calculated using the following formula: Beta=2ρ/PP×ln(SBP/DBP)×PWV2, where ρ, SBP, DBP, and PP are blood density, and systolic, diastolic, and pulse pressures, respectively. aBeta, ifBeta and aortic-iliac-femoral Beta (aifBeta) were calculated using aPWV, ifPWV and aifPWV, respectively. Results: aBeta and aifBeta increased, while ifBeta decreased significantly during the decreased BP induced by the bleeding. Reverse reactions of those indices were observed by transfusing the removed blood. Conclusion: total arterial stiffness (aifBeta) increased, however, the elastic and muscular arteries stiffened and softened during the bleeding, respectively. These results would give useful diagnostic information during fall in BP.