The influence of haematocrit and fibrinogen concentration on vascular resistance

Barrie, William Wright (1979) The influence of haematocrit and fibrinogen concentration on vascular resistance. MD thesis, University of Glasgow.

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Obstructive arterial disease is common and is a major source of morbidity. It is frequently not amenable to direct surgery, but there is no effective form of medical therapy. The use of vasodilator drugs to lower vascular resistance has been discredited. Although in theory flow should be increased by reducing blood viscosity, the flow properties of blood are complex and unpredictable in vivo. In vitro blood viscosity increases enormously at very low shear rates and a yield stress exists (that is a finite minimum force is required for flow to start). These properties are related both to haematocrit and the presence of fibrinogen, and would be of great therapeutic potential if reflected in vivo, since plasma fibrinogen concentration, and to some extent haematocrit can be safely manipulated. Initially a simple canine model was used to investigate the effect of defibrinogenation on blood flow. A critical arterial stenosis was created in one femoral artery and electromagnetic flowmeters used to measure flow through both femoral arteries and cardiac output. In both limbs of the control animals and in the non ischaemic limb of the defibrinogenated animals flow decreased as did cardiac output. However, in the ischaemic limb of the defibrinogenated animals flow relative to cardiac output increased significantly after defibrinogenation suggesting that fibrinogen might be important in low flow states. These experiments were not conclusive however as the influence of changes in vasomotor tone or coagulation could not be excluded. To try to exclude influences other than blood viscosity, an isolated canine hind limb preparation was devised in which fresh anticoagu1ated canine blood at 37

Item Type: Thesis (MD)
Qualification Level: Doctoral
Additional Information: Adviser: W G Schenk
Keywords: Physiology
Date of Award: 1979
Depositing User: Enlighten Team
Unique ID: glathesis:1979-72812
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 11 Jun 2019 11:06
Last Modified: 11 Jun 2019 11:06

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