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The relationship between the blood flow and the marrow cavity pressure of bone

University of British Columbia

An experimental animal model was developed to study and define the relationship between the blood flow and the marrow cavity pressure of bone. The study was carried out in 24 rabbits and 32 dogs under nembutol anesthesia. A multichannel physiograph was used to record simultaneously the systemic blood pressure, bone blood flow, marrow cavity pressure of bone and time sequence. The systemic blood pressure was measured by cannulating a brachial or carotid artery. The bone blood flow was measured by cannulating the nutrient vein and/or the nutrient artery. The marrow cavity pressure was measured by inserting a steel cannula through a drill hole in the cortex into the marrow cavity. The bones studied were mainly the tibia and femur. During the normal control condition, the marrow cavity pressure was found to have a wide range from animal to animal. In the rabbits, the range was from 20 to 60 mm. Hg. (15 to 50 percent of the systemic blood pressure). In the dogs, it ranged from 40 to 120 mm. Hg. (20 to 90 percent of the systemic blood pressure). However, the systemic blood pressure, intramedullary pressure and nutrient venous outflow were remarkably constant in a control period, therefore, their changes under experimental conditions were readily recordable. Various factors affecting bone circulation were studied. If the femoral vein is occluded the marrow cavity pressure rises and the nutrient venous outflow increases indicating venous congestion of bone. Nutrient artery occlusion causes a sharp fall in marrow cavity pressure coupled with a marked decrease in the nutrient venous outflow. Adrenalin and noradrenalin intravenous infusions produce a fall in marrow cavity pressure coupled with a decreased bone blood flow, despite an elevation in the systemic blood pressure. Isoproterenol hydrochloride generally causes a fall in the systemic blood pressure, widening of the pulse pressure, a fall in the marrow cavity pressure and a decrease in the nutrient venous outflow. Electrical sympathetic stimulation produces a fall in the marrow cavity pressure and a decrease in bone blood flow. Lumbar sympathectomy causes a rise in the marrow cavity pressure and an increase in the bone blood flow. Skeletal muscle contraction produces bone venous congestion with elevation of the marrow cavity pressure and increased nutrient venous outflow. Muscular relaxation causes a momentary sharp fall in the marrow cavity pressure to sub control levels before returning to the normal pressure. It is concluded that the marrow cavity pressure is bone blood flow dependent and reflects well the changes in the hemodynamics of bone. The narrow pressure rises if the arterial blood supply to bone increases or the venous congestion occurs in bone. The marrow pressure falls if the arterial blood supply to bone decreases or the venous drainage of bone is facilitated.

Text

2011-04-29

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http://hdl.handle.net/2429/34145

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University of British Columbia

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