The colloid-crystalloid controversy.

The type of fluid that should be infused in the critically ill patient remains controversial. In the presence of normal lungs, maintenance of the colloid osmotic pressure (COP) can limit the development of pulmonary edema when the hydrostatic pressure is raised. When the permeability of the lung capillaries is altered, the influence of the type of fluid on the lung function becomes minimal. The larger increase obtained in extravascular fluids by the use of crystalloids could limit the availability of cellular oxygen. Nevertheless, differences in morbidity and mortality have not been related to the type of fluid infused, suggesting that the amount of fluid is a more important factor.