Pulmonary and Extrapulmonary Effects of Increased Colloid Osmotic Pressure During Endotoxemia in Rats: Extrapulmonary Effects of COP
Hetastarch and pentastarch infusion in hypopro-teinemic sheep, unlike our endotoxemic albumin-treated rats, have produced a limited transvascular fluid filtration in the lung and soft tissue compared to crystalloid infusion. This, however, was explained by the augmentation of plasma COP and by the plasma-to-lymph oncotic pressure gradient, where capillary integrity was maintained. Conflicting reports of the role of COP in the formation of organ edema indicate that the other Starling forces have significant but varying influence on edema genesis. Mehlhorn et al reported that increasing the COP of normothermic blood cardioplegia minimizes myocardial edema, thus preventing post-cardiopulmonary bypass cardiac dysfunction. Long-term high-colloid oncotic therapy was found to be effective in reducing ischemic brain edema in gerbils. In a rat model, reduced COP aggravated brain edema after mild-to-moderate mechanical head injury.
Interstitial pressure is another factor that influences fluid flux across the capillary membranes. This pressure in muscles is equal to 0 mm Hg. Although negative values are found in the lung, positive pressures are recorded in organs with tight capsules such as the kidney, in which values of8 to 10 mm Hg have been reported. Interstitial compliance and interstitial pressure are different in various organs. This also may be one of the factors responsible for the varying degree of interstitial edema formation in different organs. Thus, while an increase in capillary permeability during sepsis is generalized, it may affect different organs to various degrees. Increased water content may disturb functional activity by reducing tissue oxygenation. This may contribute to multiple organ dysfunction, as seen in sepsis and other systemic inflammatory reaction syndromes. buy asthma inhalers online
Albumin treatment both with and without endo-toxemia led to significant decreases in Hb levels (Fig 2), probably due to hemodilution. This may increase transcapillary fluid movements by affecting plasma COP, the capillary surface area, or capillary perme-ability. Thus, albumin administration for increasing COP may indirectly affect O2 carrying capacity. Alternatively, the easiest way for increasing COP is to give large doses of diuretics, whereas the easiest way of reducing COP is to give large volumes of crystalloids. Furosemide, a diuretic agent, has been shown to enhance pulmonary edema clearance in dogs. Whether increasing COP by giving furo-semide or other diuretic agents will improve multi-ple-organ edema during endotoxemia warrants further investigation.
Artificially increasing COP by albumin administration, in the face of early global capillary leak syndrome, aggravates pulmonary dysfunction and appears to have no beneficiary effect on endotoxin-induced lung, kidney, or heart edema.