Proposition of a technique to assess the vasoactive effects of hemoglobin-based oxygen carrying solutions in vivo: Preliminary results in the rabbit aorta

Most of hemoglobin-based oxygen carriers (HBOCs) increase the blood pressure after injection in the blood stream by a mechanism involving one or more factors that contribute to the regulation of the vascular tone. Many techniques make it possible to study the vascular effects of HBOCs both in vivo and in vitro. The in vivo methods assess the blood pressure and some estimated regional blood flows (use of radioactive or colored microspheres). Measurements of the real vessel diameter and blood flow would be useful to understand hemoglobin-mediated vasoconstriction mechanism. Our purpose was to elaborate an experimental model in anesthetized rabbits to monitor the diameter and the blood flow velocity in the same vessel in order to calculate the absolute blood flow. The blood flow velocity (in cm/s) was assessed by pulsed Doppler velocimetry and the diameter (in mm) was assessed by a technique of Wall Tracking. The first results indicate that the method is well adapted to study the effects of resuscitative fluids (plasma and blood substitutes) on the aorta vascular tone after hemodilution or resuscitation from severe hemorrhage.