Disturbed Blood Flow and Hemodynamics

Disturbed Blood Flow and Hemodynamics - Disturbed Blood...

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Disturbed Blood Flow and Hemodynamics Survival of cells and tissues is dependent on the oxygen provided in the blood supply as well as on a normal fluid balance; 60% of body weight is water (40% intracellular; 15% interstitial—extracellular; 4% plasma—extracellular) Edema Accumulation of abnormal fluids in the interstitial/intercellular tissue → swelling of the subcutaneous tissues (water under skin); disturbance in hydrostatic and oncotic pressure between capillary and interstitial fluid Mechanism: Normal control depends on : Starling’s Law; local factors (lymphatic obstruction, vascular permeability); systemic factors (cardiovascular function, overall fluid balance, salt retention); physiological ranges (intravascular pressure, osmolarity) Starling’s Law= movement of fluid between vessels and tissue governed by balance between 4 forces: 1. Hydrostatic pressure in vessel which measures 32mmHg at arterial end and 12mmHg at the venous end; pushes water out; force exerted by fluid against capillary wall; forces fluid out of capillaries; O2 and nutrients move into surrounding tissue; need to remove CO2 /waste from tissues into capillaries where they are less concentrated (via oncotic pressure) 2. Oncontic pressure= colloid osmotic pressure (COP) of plasma (26mmHg) which reflects the amount of serum protein (albumin); keeps water in; created by presence of large molecules that can’t diffuse and are prevented from moving through capillary membrane; doesn’t vary between arterial/venous ends 3. Interstitial pressure (tissue tension)= 3-4mmHg 4. Tissue fluid osmotic pressure (very low) Diffusion= movement from [high] →[low] Net filtration pressure= hydrostatic – oncotic pressure Fluid will leave if hydrostatic > oncotic (aterial end); NFP= +6mmHg Fluid will enter if hydrostatic < oncotic (venous end); NFP= -14mmHg **most important are the HP and OP of the plasma *intravascular HP and interstitial fluid osmotic pressure tend to move fluid OUTWARD; interstitial fluid pressure and plasma OP draw fluid INWARD Deoxygenated blood returns to R side of heart Central Circulation= systemic (to periphery); pulmonary Lymphatic Circulation= adjacent to capillary vessels 50% of total blood proteins leak out of capillaries 14 ml fluid into interstitial fluid; back into venous capillary (9/10); lymphatics (1/10) Veins/arteries meet at capillary network Edema will occur when there is: 1. An increased in intravascular hydrostatic pressure due to increased venous pressure (hydrostatic > oncotic; water out; reabsorption decreases and lymphatics drain more than 10%); ex. Congestive heart failure (right side failure→ peripheral edema=cant pump blood as effectively; pitting edema); left side failure→ lung edema); ex. Deep venous thrombosis of lower legs (one side only= localized; blood clot in venous
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circulation); hydrostatic edema= hydrostatic pressure at venous end of capillary is
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This note was uploaded on 02/08/2012 for the course PATHOLOGY 3245 taught by Professor X during the Spring '11 term at UWO.

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Disturbed Blood Flow and Hemodynamics - Disturbed Blood...

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