HEMODYNAMICS OF BONE MARROW CIRCULATION

In 44 anesthetized rabbits the femur was perfused in situ through the nutrient artery by blood led through an extracorporal perfusion arrangement from the left carotid artery. Blood inflow, perfusion pressure and intramedullary venous pressure were recorded. At perfusion pressures of 110 to 150 cm of saline (80 to 110 mm of Hg) blood flow in the different animals ranged from 0.1 to 1.2 ml/min × g wet marrow tissue, and intramedullary venous pressure from 10 to 80 cm of saline (7 to 60 mm of Hg). Flow and intramedullary venous pressure both increased with the perfusion pressure whereas flow decreased and intramedullary venous pressure increased when the venous pressure outside the bone increased, showing that in the bone marrow both an arterial and a venous resistance were present. The predominant effect of noradrenaline was to constrict, and of acetylcholine to dilate arterial vessels. No reactive hyperemia could be demonstrated upon occlusion of the arterial inflow. The arterial vessels showed only a weak ability to autoregulate flow. The venous resistance varied greatly from one preparation to another, differing from only a small fraction of—to more than half the total vascular resistance in the bone marrow. It stayed constant or increased with increasing perfusion pressure, thereby causing the pressure‐flow relationship curves to differ from convex against the pressure—to convex against the flow axis. The hemodynamic properties demonstrated were explained as being due to the unusual vascular anatomy and the rigid enclosement of the bone marrow. © 1968 Scandinavian Physiological Society