Chapter 2 where V = filtered volume, k = filtration coefficient, HP = hydrostatic pressure, c = capillary, i = interstitial fluid, gc = subendothelial glycocalyx, σ = membrane pore size, COP = colloid osmotic pressure, and Q = lymph flow. Figure 2-1 The main components of the Starling-Landis equation that affect intravascular water content include intravascular hydrostatic pressure (HP) and colloid osmotic pressure (COP). The intravascular HP is a result of intravascular volume, cardiac output (CO), and systemic vascular resistance (SVR). Under normal conditions the HP favors the movement of fluid from the vessel into the interstitium. The COP is the force that opposes intravascular HP, supporting intravascular water retention. The COP is generated by the presence of large molecules (primarily proteins) that do not readily pass the capillary membrane and create an osmotic effect. The dynamics of normal fluid movement across the capillary membrane can change with certain diseases. Fluid moves from the intravascular to the interstitial or third-space compartment under certain conditions (Figure 2-2 and Table 2-1). Plasma COP can increase with water loss (hemoconcentration), remain the same when there is acute hemorrhage, or decrease with protein loss. In addition to capillary dynamics, the composition of intravenously administered fluids determines how these fluids are distributed across fluid compartments. Figure 2-2 Fluid can pass out of the intravascular space under several conditions listed in Table 2-1: increased intravascular hydrostatic pressure (HP), increased capillary permeability, decreased filtration coefficient, and decreased intravascular colloid osmotic pressure (COP). These conditions lead to the consequences of peripheral edema and hypovolemia. A 5-g lyophilized canine albumin (www.ABRInt.net) recently has been developed for use as a replacement colloid in the treatment of hypoalbuminemia in dogs. It is stored in a dehydrated powder form and reconstituted with isotonic saline to a desired concentration. Information on its clinical use is limited to albumin replacement in dogs with hypoalbuminemia and septic peritonitis, but not for volume replacement.
Colloid Fluid Therapy
Fluid Dynamics
Albumin
Colloid Fluid Therapy
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